Coping with mortality: responses of monkeys and great apes to collapsed, inanimate and dead conspecifics

Coping with mortality: responses of monkeys and great apes to collapsed, inanimate and dead conspecifics. Arianna De Marco, Roberto Cozzolino & Bernard Thierry. Ethology Ecology & Evolution, Mar 21 2021. https://doi.org/10.1080/03949370.2021.1893826

Abstract: It was long assumed that only humans can distinguish the living from the dead. Renewed interest in this question over the last decade has led several authors to assert that non-human primates are also aware of death. We investigate this issue by comparing the behaviours of monkeys and great apes toward helpless conspecifics, basing our analysis on published reports. We first examine the behaviours of mothers towards the body of their dead offspring. They may carry the corpse for days or more before abandoning it. They groom, inspect and protect it, sometimes allowing group members to explore it, and rare cases of cannibalism have been reported. No significant difference is observed in the way that monkeys and great apes treat the bodies of infants. We then examine responses to collapsed (still able to move and react) and inanimate (unresponsive or dead) conspecifics. Monkeys and great apes guard, care for and inspect their helpless partners, and also manipulate and mobilise them. Through these actions, individuals may inform themselves about the state of their partners, test their responsiveness and/or attempt to rouse them. It appears that only chimpanzees and gorillas show violent action such as display behaviours and the rough treatment of bodies. They can also make distress calls, and periods of “stunned silence” sometimes occur in chimpanzees, indicating that they are experiencing intense emotion. Finally, we argue that while both monkeys and great apes detect body dysfunction through the victims’ inability to wake up and move, only great apes can understand that something serious has happened. The signs of emotional disturbance reported in them indicate that they may believe that inanimate conspecifics have entered a state of “dormancy”, meaning that they are unlikely to regain wakefulness. However, there is no evidence that any non-human primates are aware of mortality.

Keywords: deathemotiondistressempathymental representationepimeletic behaviourprimate

RECOGNITION OF DYSFUNCTION AND AWARENESS OF MORTALITY

Since death is the cessation of life, it may seem necessary to know what primates understand about life in order to know what they understand about death. Animals are defined by their animacy, and it has been shown in several animal species, including primates, that individuals are able to distinguish between animate and inanimate as human infants do: they can separate entities that engage in self-generated motion from those that do not (Opfer & Gelman 2011; Tsutsumi et al. 2012; Abdai et al. 2021). Some authors have proposed that animals and humans are endowed with several innate systems of “core knowledge” that are designed to build representations with specific contents. One system would serve to represent (inanimate) objects and their mechanical effects, while another would serve to represent (animate) agents and their actions (Spelke & Kinzler 2007; Carey 2009). On the basis of this theoretical framework, Gonçalves and colleagues (Gonçalves & Biro 2018; Gonçalves & Carvalho 2019) hypothesize that when a living being dies, its body becomes an object, thus activating both the object and agency core systems in bystanders. This would create a perceptual mismatch in them, resulting in an “animacy detection malfunction”.

It is sound to consider that an inanimate body can present contradictory clues that do not meet the expectations of conspecifics, and hinder their ability to recognize its state. However, it is probably too early to assert that the perception of a corpse induces a conflict between an object representation system and something like a life representation system. We are far from knowing what dynamic clues subjects use to assess animacy, and as Gonçalves and Carvalho (2019) acknowledge, agency involves much more than animacy: agents are capable of attentional states, goal-directed movements and interactions with others; primate species probably vary in their ability to identify these different components of agency. Moreover, subjects can also identify living beings like animals using morphological features such as the presence of a face, eyes, limbs or species-specific characteristics, and we do not know how dynamic and morphological clues are integrated at the brain level (Opfer & Gelman 2011; Fisher & Freiwald 2015). We should add to these multiple clues the past interactions and social relationships that a subject may have memorized about a given conspecific, which would also contribute to the subject’s representation of this individual.

Rather than starting from theoretical constructs about the recognition of life by primates, it seems more productive for the time being to address what they understand about the state of their inanimate conspecifics. However, discriminating inanimate individuals from perceptual features is not the same as knowing what it means to be dead (Allen & Hauser 1991; Monsó 2020). In what follows, we will examine in turn whether monkeys and great apes detect conspecific dysfunction, show signs of disturbance, and exhibit some awareness of mortality.

Detection of dysfunction

Although death is usually regarded as an event, it is more accurate to think of it as a process in which one organic function fails after another. In principle, it would thus be possible to detect the dysfunction of a body using different clues: cardiorespiratory arrest, cessation of eye movements, and the inability to move and react.

As previously reported, monkeys and great apes have been observed inspecting the face and/or mouth of collapsed or inanimate partners, and Anderson et al. (2010) wrote that the companions of a dying chimpanzee “appeared to test for signs of life by closely inspecting her mouth and manipulating her limbs (test for pulse or breath)”. However, nobody ever saw a monkey or an ape move their ear close to the mouth of another to listen to his/her breathing; nobody ever saw a monkey or an ape put their hand on the chest of another to feel his/her heartbeat. Not only would the contrary imply expectations about the need for breathing and heartbeats, but it is even hard for humans to be certain that the lungs and heart have stopped, especially in weakened individuals (Stewart 2003). Historically, people waited for signs of putrefaction to confirm death. Until a few centuries ago, tests for respiratory ventilation consisted for example of placing a feather under the nose, or holding a mirror before the mouth to detect condensation; it was only with the invention of the stethoscope in the 19th century that medical practitioners were able to determine with a reasonable degree of certainty whether the heart had ceased to function (President’s Commission 1981; Powner et al. 1996; Whetstine 2008). Against this background, it seems unlikely that primates other than humans have the ability to use soundless breathing, heart rate or pulse to assess the state of their conspecifics.

Another long-established medical sign of decease has been the fixity of the eyes (President’s Commission 1981; Whetstine 2008). This is understandable given the normal animation of the eye area, which includes gaze orientation, pupillary reflex, and eyelid movements. Experimental studies in humans and other primates have shown that they are disproportionally interested in the eye area; they are highly sensitive to the attention and gaze direction of others, and are able to adjust their behaviour to get a partner to attend to them (Emery 2000; Bourjade et al. 2014; Liebal et al. 2014; Tomasello & Call 2019). Correspondingly, monkeys and great apes often inspect the face and/or eyes of collapsed and recently deceased conspecifics (Tables 1–2). It is safe to assume that they are able to detect the absence of eye movement. The inability to make eye contact and get attention may warn them that something is going wrong with their companion. We can note that the eyes of inanimate individuals may be open or closed, but this information is not found in scientific reports. Fingering or picking at the eyes or eyelids has sometimes been observed in monkeys (Yerkes 1915; Fashing et al. 2011). According to a second-hand account, chimpanzees were once seen opening the eyes of a dead companion (Bekoff 2007).

Even if animacy is a main attribute of animals, it is common for primates to encounter motionless conspecifics. They regularly experience periods of immobility, which are first and foremost due to sleep phases. It is not the lack of animacy per se that must seem odd to observers of motionless individuals, but rather their inability to regain animacy: they are expected to wake up when someone acts on them, and the problem arises when they fail to do so. Assessing the responsiveness of partners and probing or stimulating them may account for many of the behaviours of primates towards collapsed and inanimate conspecifics. Although observing and sniffing can provide initial information, it is only by touching and above all handling partners that group members can test their reactivity or attempt to rouse them – with rough treatments producing the same effects. Whatever the exact goals of the intervening individuals, their actions can inform them if their partners were previously asleep or if something is going wrong. This is not an issue for collapsed partners, as they may still show some movement; we have indeed found that manipulative actions were mainly reported for inanimate partners, further indicating that monkeys and great apes are able to discriminate between these two conditions (Table 2). Note that we would expect the opposite trend for mobilising actions that specifically seek to lift a partner and restore him/her to an upright position: if the performers are able to distinguish between the two conditions, these actions should be applied to apparently wakeful – i.e. collapsed – partners rather than to inanimate ones. As already mentioned, only two unambiguous cases of this type of helping behaviour have been described. In the first instance a mountain gorilla attempted to pull a juvenile into a sitting position while the latter was still reactive (Watts 2020: case 1). In contrast, the second instance concerns a rhesus macaque who tried to lift a partner when the partner was inanimate, and did so again when the partner was beginning to regain consciousness after fainting (see Supplemental Material). There are too few cases to be able to draw firm conclusions.

The termination of breathing, heartbeat, eye movements and any reflex or motor response is referred to by medicine as negative signs of life. They are later followed by positive signs of death: cooling of the body, stiffening, putrid odours and changes in skin colour that result from the decomposition process. These different alterations gradually take the body away from its living appearance, which could contribute to the information – or confusion – of those who inspect it (Gonçalves & Biro 2018). However, positive signs of death do not appear until several hours or even more than a day after death, so in many cases group members have assessed the state of the affected partner long before this time.

It may be expected that the more experienced individuals are better at detecting unresponsiveness and other signs of death. Three studies have compared the duration of dead infant carrying in females of different age and maternal experience. This yielded contradictory results that provided little support for the hypothesis that younger and/or first-time mothers would carry their dead infant for longer periods of time than other mothers (Sugiyama et al. 2009; Das et al. 2019; Lonsdorf et al. 2020). Besides, younger chimpanzees tend to exhibit more exploratory behaviours toward corpses than adults (Teleki 1973a; Stewart et al. 2012; van Leeuwen et al. 2016; Jakucińska et al. 2020), and it is not rare for them to play with the bodies of dead infants (see above). However, little quantitative data are available in primates about the tendency of different age-and-sex categories to examine the body of affected conspecifics (see De Marco et al. 2020).

Signs of disturbance

In the foregoing, we deliberately used the vague expression “something is going wrong” to account for what primates can infer when faced with a conspecific’s inability to respond to their actions. The question now is whether this can cause concern to subjects. Not understanding something is not necessarily a reason for worry. On the contrary, if primates understand that something serious has happened, it can be disturbing to them and can be reflected in their behaviour.

Several authors have claimed that the occurrence of affiliative behaviours towards collapsing or dying conspecifics is a mark of compassion (Bezerra et al. 2014; Yang et al. 2016; Gonçalves & Carvalho 2019). However, the affected individuals in these situations can move and emit sounds, so partners may respond to their signs of distress without the need for a mental representation of their emotional states. If compassion implies an understanding of distress that involves empathic perspective-taking or the sharing of feelings (Cheney & Seyfarth 2007; Boesch 2012; Adriense et al. 2020), then responses to the behavioural expression of distress are not proof of compassion. On the other hand, there is converging evidence that great apes such as chimpanzees are capable of targeted helping and empathic perspective-taking, and can thus apprehend the suffering of conspecifics (de Waal 2008; Boesch 2012; Pérez-Manrique & Gomila 2018; Sato et al. 2019). Nevertheless, when chimpanzees display affiliation towards a dying conspecific, it is difficult to justify any assumption that this a caretaking behaviour anticipating an approaching death (Anderson et al. 2010): an individual who is collapsing or dying is by definition still alive; we have no reason to believe that others can predict she/he is going to die, and they may actually perceive her/him as rescuable. Stringent conditions are necessary to examine whether a companion’s physical condition may disturb partners, regardless of the occurrence of any communicative cues. We must rule out reactions to collapsed conspecifics and focus on reactions to inanimate conspecifics. We must also exclude cases where the presence of a danger in the surroundings can elicit distress or warning calls from bystanders (e.g. Mohnot 1980; Gupta 2000; Perry & Manson 2008: Maní/Pobrecito; Riley et al. 2015; Campbell et al. 2016: case 4).

The display behaviours and rough treatments that chimpanzees and gorillas show towards their inanimate conspecifics are among the most dramatic responses reported in animals (Table 2). Males are primarily responsible for these actions, which in some cases were repeated over several hours (Fossey 1983; Stewart et al. 2012). Even though rough treatments may contribute to test or awaken the partner, the energy devoted to violent behaviours indicates that the individuals’ motivations go beyond these goals. Regardless of whether this behaviour expresses frustration due to incomprehension or a lack of acceptance of the partner’s state, it at least informs us that individuals find the situation serious enough to engage in such heated action. The alternation of periods of quiet attendance and periods of excitement is another hallmark of the chimpanzee response. Emotional displays may include warning and distress calls, while stillness may pervade the entire group in cases of stunned silence (see above). Here again, signs of intense emotional disturbance in chimpanzees indicate that they attribute a special meaning to the unresponsiveness of their companion. No comparable periods of stunned silence have been recorded in gorillas, but it is difficult to make inferences about this difference with chimpanzees because gorilla temperament is characterized by high emotional stability (Schaeffer & Steklis 2014; Eckhardt et al. 2015). No conclusions can be drawn for bonobos and orang-utans due to the lack of documented reports in these species.

The comparison of monkey behaviour with that of chimpanzees and gorillas is illuminating. No rough treatment of corpses was reported in monkeys. Display behaviours were observed once in Hanuman langurs, but they were not directed at the body of the dead individual (Mohnot 1980). Monkey responses to inanimate conspecifics are generally unremarkable. In one well-documented case in brown capuchins, for example, group members quietly inspected and handled the body of a recently deceased female in turn, and even her sister and offspring did not exhibit any signs of distress (De Marco et al. 2020). In another instance in rhesus macaques, a male made sustained efforts to revive an unconscious partner by mobilising and lifting him, and although the intervening male yawned a few times, indicating a significant degree of tension (see Maestripieri et al. 1992; Deputte 1994), he showed no evidence of being alarmed (see Supplemental Material). Likewise, the other reported cases showed no signs of distress (Table 2; see also Takeshita et al. 2020). There were two types of situation in which distress vocalisations were heard, but they do not actually contravene the previous statement. In the first case, infants cried and screamed following their mother’s death (Mohnot 1980; Fashing et al. 2011); however, these behaviours also occur as part of normal mother-offspring interactions when a female does not attend to her infant. The second situation involves mothers emitting warning, distress or contact calls when they lose the body of their dead infant. Here, the triggering event is not the infant’s lack of response, but the absence of the infant’s body, as already mentioned (Altmann & Altmann 1970: Shorty; Smuts 1985: Zandra/Zephyr; Perry & Manson 2008: Abby/Omni; Li et al. 2012: case 1; Botting & van de Waal 2020: Nurks; Carter et al. 2020: cases 1 and 5). Although monkeys sometimes display signs of tension or anxiety such as restlessness, scratching and yawning when confronted with the unresponsiveness of a conspecific (Campbell et al. 2016: case 1; Carter et al. 2020; De Marco et al. 2020; Supplemental Material), they do not show any signs of the intense emotional disturbance observed in chimpanzees and gorillas. The communicative signals that only monkeys send to non-responding conspecifics may represent a further consequence of their inability to realize the severity of their state, whereas chimpanzees and gorillas could be aware that any attempt to communicate is pointless.

Awareness of mortality

We came to the conclusion that monkeys and great apes are able to understand that “something is going wrong” when confronted with an inanimate conspecific. We also reached the conclusion that at least great apes such as chimpanzees and gorillas can also understand that “something serious has happened”. However, the question remains as to whether they are aware of what it means when a partner remains permanently inert, and whether we can gain any insight into this question. Research studies in developmental psychology have shown that the understanding of death in human children can be defined and measured through several dimensions (Speece & Brent 1984; Kenyon 2001; Slaughter 2005; Longbottom & Slaughter 2018). From 4 to 10 years of age, children successively master four main dimensions related to the concept of mortality: (1) Irreversibility: a dead individual cannot return to life, (2) Universality: all living beings must eventually die, (3) Cessation: all bodily and mental functions cease upon death, (4) Causation: the breakdown of bodily functions is due to external and internal causes.

Irreversibility is probably the easiest dimension of mortality to grasp, as it is the first dimension that children successfully master. Several authors have expressed the opinion that primates are capable of understanding the permanence of death (de Waal 2013; Anderson 2018; Gonçalves & Carvalho 2019). de Waal (2013) reports an anecdote where a film was projected to a group of captive chimpanzees. The film showed a male from the group who had died a few years earlier, and his appearance on the screen provoked a strong emotional reaction from his former rivals. Gonçalves and Carvalho (2019) argue that their reaction was evidence of a violation of expectation regarding the irreversibility of death. However, this event is by no means conclusive, as it could just as well be used to support the view that chimpanzees accept that dead individuals can return to life, and be touched if this appears to happen. Other researchers claim that the weakening of the mother’s attachment to her dead infant and her eventual abandonment of the corpse prove her awareness of the irreversibility of death (Das et al. 2019; Lonsdorf et al. 2020; Monsó 2020). If it were true, however, this explanation would be tantamount to asserting that mothers of any animal species who give up the putrefying body of their offspring are aware of the irreversibility of death. One might just as well reason ad absurdum that chimpanzee females are among the least cognitively gifted primates since more than half of them in the Gombe population carry their dead offspring (see Lonsdorf et al. 2020). It is more straightforward to say that mothers have no other choice but to abandon the corpses after some time, and that this behaviour tells us nothing about death awareness in primates.

Anderson (2011, 2018) points out that chimpanzees have many opportunities to learn that inanimate individuals generally do not wake up, not only because they are exposed to deceased conspecifics – infant death being the most common event – but also because they regularly capture animals that they may kill and handle for a period of time before consuming them. Indeed, these different experiences are likely to inform individuals that subjects who remain immobile for extended periods of time generally do not recover. It should be noted however that small animals of a wide range of taxa follow death-feigning anti-predator strategies in which they go into tonic immobility when captured (Humphreys & Ruxton 2018). This means that it is not uncommon for primates to encounter motionless animals, some of which can subsequently resume activity. It should also be remembered that witnessing sleeping and awakening sequences in others is a daily reality for them. Furthermore, individuals may have also seen unconscious partners who later recover, because they were temporarily ill or had passed out. For example, falling from a tree is a continuing risk for tree-dwelling animals (see Table 2); primates cannot avoid occasionally landing on a dead branch, and if they fail to catch hold of a lower branch, they may pass out or die when they hit the ground, depending on the distance they fall and the nature of the ground. Waking up is instantaneous in a sleeping partner, whereas it may seem delayed in an unconscious partner. The consequence is that it is always difficult for primates to predict what will happen to an inanimate conspecific because the possibility that she/he may recuperate can rarely be excluded. The occurrence of visitations points in the same direction. By returning to a body they have previously left, they can check if their companion is still in the same state.

Children grow in a world of cultural symbols and conventions, and the representations embodied in the human language help them to form abstract categories (Tomasello 1999; Carey 2009). The words “death” and “dead” are offered to them as tools that are passed on from one generation to the next (Renfrew 2016). Yet it takes years for them to understand that terms such as “never”, “always” or “definitely” can have absolute meaning (Kuczaj 1974; Hoffner et al. 1990). In comparison, animals are solipsist thinkers, meaning that they learn by themselves. They receive no support from others that would help them to conceptualize the absolute dimensions of death. While great apes can learn that unresponsive companions may not recover, this is probabilistic knowledge and not the absolute knowledge implied by words such as “irreversibility” and “permanence”. Rather than asserting that great apes may be aware of the irreversibility of death, it seems more appropriate to echo Boesch’s (2012) formulation that chimpanzees may be able to “realize dead individuals do not move or need help anymore, and that they will remain inanimate”. This knowledge involves some uncertainty; it may reflect the belief that these individuals have fallen into a state where they seem to remain asleep indefinitely. We propose to call this state “dormancy”, which means that the individual is in a prolonged state of immobility that is not normal sleep, with no rule specifying that recovery is excluded. In terms of the conceptualization abilities required, belief in dormancy is a less costly hypothesis than an awareness of the irreversibility of death.

Like irreversibility, the second dimension of mortality, universality, has an absolute meaning. We cannot question primates directly like we do with children, and there is no indication to date that they are able to know that death happens to everyone, whether they are conspecifics or individuals of other species (Anderson 2018). The third and fourth dimensions of mortality are the last to be mastered by children because they involve basic knowledge about the biological properties of living beings and the body functions that maintain life (Slaughter 2005). Some authors assume that primates recognize death as the cessation of bodily functions, basing their reasoning on the fact that mothers handle and defend the body of their dead infant (Das et al. 2019), or on changes in maternal behaviour such as atypical carrying postures, distancing from the corpse and its final abandonment (Lonsdorf et al. 2020). However, the first argument ignores the fact that mothers also handle and defend their live infants (Gonçalves & Carvalho 2019), and the second fails to distinguish between detection of dysfunction and awareness of mortality: mothers may be able to recognize that something is going wrong with their non-responding infant without necessarily understanding what has happened (see above). The fourth main dimension of mortality, causation, is particularly demanding on the cognitive level since it requires subjects to infer causal relations, i.e. formulate hypotheses about the mechanisms involved in the breakdown of the functioning of the organism. It has been suggested that prey killing and lethal attacks on conspecifics may help individuals to gain insight into the causes of death (Anderson 2018), and also that the investigation of inanimate bodies would enable the understanding of these causes (Das et al. 2019). However, it should be clear that inspecting corpses or even inflicting death on others – as all predators do – is by no means proof that they realize how death occurs. Several authors have argued, based on a limited number of cases, that individuals react differently to deceased partners depending on the cause of death, but the views expressed by these authors are conflicting. According to Anderson and collaborators (Anderson 2011; Yang et al. 2016; Pettitt & Anderson 2020), sudden and traumatic deaths resulting from an accident or a killing would trigger more alarm and violent behaviours than deaths due to non-apparent causes such as illness. In contrast, Boesch (2012) proposes that bodies with wounds generate fewer signs of fear and alarm in chimpanzees than those of individuals who die from unexplained causes such as illness. Whatever the case, the accumulation of reports in chimpanzees and other species indicates that none of these expectations have been confirmed, either for dead infants (Rajpurohit 1997; Watson & Matsuzawa 2018), or other inanimate conspecifics (Table 2).

While the absence of evidence is not evidence of absence, the burden of proof rests on the person who asserts that something exists, and not on the person who denies it. Monsó (2020) looked for behaviours that would demonstrate that animals understand death, but she only proposed signs of emotional disturbance and ways to detect the dysfunction of the body. To date, there is no evidence that primates, including great apes, have an absolute concept of death, whatever the dimension considered, be it irreversibility, universality, cessation or causation. At this point, it is important to notice that irreversibility differs from the other three dimensions in two major respects. First, irreversibility can be reduced to a more concrete notion such as dormancy. To bystanders, a dormant conspecific may appear to be a sleeping individual who fails to wake up despite repeated interactions with her/him, and who remains in this state for an indefinite period of time. It is also conceivable that experienced individuals may have learned that it is common for a dormant body to cool down, smell, be surrounded by flies, and gradually lose its shape. Second, the awareness of the mortal condition of all living beings or the biological functions involved in the cessation of life and the causation of death is very abstract knowledge with little emotional content. These three dimensions of mortality cannot account for the strong emotional commitment revealed by the behaviour of great apes such as chimpanzees and gorillas. On the contrary, the ability to conceive of irreversibility or dormancy may explain that they understand something serious has happened. Realizing that the inanimate individual in front of them is unlikely to come out of sleep, unlikely to revert to the way she/he was, and must be left behind, can induce intense emotional disturbance. This may explain the display behaviours and rough treatments that have been recorded in chimpanzees and gorillas, reflecting a lack of comprehension and/or acceptance that their companion remains in an inanimate state. This may also explain the distress calls and episodes of stunned silence reported in chimpanzees. Some authors consider that such behaviours indicate an awareness of the irreversibility of death (Anderson 2017; Monsó 2020). As discussed earlier, we find it more accurate to attribute these responses to the belief that their partner has gone into a dormant state. Belief in dormancy represents a more parsimonious explanation that does not require the involvement of concepts of mortality that may be too abstract to belong to the cognitive realm of great apes.

Personality traits relate to both STEM preferences & specialization; extraversion & agreeableness are the strongest predictors of not chosing STEM; this trend is even stronger for girls (vs boys)

Personality traits, preferences and educational choices: a focus on STEM. Johan Coenen, Lex Borghans, Ron Diris. Journal of Economic Psychology, March 22 2021, 102361. https://doi.org/10.1016/j.joep.2021.102361

Rolf Degen's take: "Nice" personality traits are associated with lower preferences for STEM fields, even more so among females

Highlights

• Personality traits relate to both STEM preferences and STEM specialization

• Openness and Agreeableness are the best predictors of STEM preferences

• Extraversion is the strongest predictor of actual choice for STEM

• Cognitive skills become more important when moving from preferences to actual choice

• There are markedly different patterns for boys compared to girls

Abstract: Around the developed world, the need for graduates from Science, Technology, Engineering and Mathematics (STEM) fields is growing. Research on educational and occupational choice has traditionally focused on the cognitive skills of prospective students, and on how these determine the expected costs and benefits of study programs. Little work exists that analyzes the role of personality traits on study choice. This study investigates how personality traits relate to preferences of students for STEM studies and occupations, and to specialization choice in high school. We use a rich data set that combines administrative and survey data of Dutch secondary education students. We find that personality traits are related to both the preference that students have for STEM as the actual decision to specialize in STEM studies, but to different degrees. We identify significant relations with preference indicators for all Big Five traits, especially for Openness to Experience (positive), Extraversion and Agreeableness (both negative). The size of these relations is often larger than those between cognitive skills and STEM preferences. Personality traits are comparatively less important with respect to the actual specialization choice, for which we identify a robust (and sizable) negative relation with Extraversion, and for girls find a positive relation with Openness to Experience. The results suggest that once students have to make actual study choice decisions, they rely more on cognitive skills rather than personality traits, in contrast to their expressed preferences.

Keywords: PersonalityEducational choiceSTEM

The digit ratio (2D:4D) is considered a proxy for testosterone exposure in utero; it doesn not predict economic preferences

2D:4D does not predict economic preferences: Evidence from a large, representative sample. Levent Neyse, Magnus Johannesson, Anna Dreber. Journal of Economic Behavior & Organization, Volume 185, May 2021, Pages 390-401. https://doi.org/10.1016/j.jebo.2021.02.029

Abstract: The digit ratio (2D:4D) is considered a proxy for testosterone exposure in utero, and there has been a recent surge of studies testing whether 2D:4D is associated with economic preferences. Although the results are not conclusive, previous studies have reported statistically significant correlations between 2D:4D and risk taking, altruism, positive reciprocity, negative reciprocity and trust. However, most previous studies have small sample sizes gathered from university students and there is also no consensus on the type of analysis (e.g., which hand to analyze or subgroup to focus on) or the preference elicitation method. We present results from a pre-registered large sample study testing if 2D:4D is associated with economic preferences. Data were collected in a representative sample of adults in the German Socioeconomic Panel-Innovation Sample (SOEP-IS), in a sample of about 3450 respondents (about 5 times larger than the previously largest study in this field). Using experimentally validated survey questions, we find no statistically significant association between 2D:4D and economic preferences in the largest study to this date on the topic.

Keywords: Economic behaviorPrenatal hormonesTestosteroneDigit ratio

The tendency to perceive an electoral outcome as foreseeable is positively & consistently associated with satisfaction with the outcome

Hindsight Bias and Electoral Outcomes: Satisfaction Counts More Than Winner-Loser Status. Mauro Bertolotti and Patrizia Catellani. Social CognitionVol. 39, No. 2, March 2021. https://doi.org/10.1521/soco.2021.39.2.201

Abstract: The tendency to perceive outcomes as more foreseeable once they are available is a well-known phenomenon. However, research on the cognitive and motivational factors that induce individuals to overestimate the foreseeability of an electoral outcome has yielded inconsistent findings. In three studies based on large-scale electoral surveys (ITANES, Italian National Election Studies), we argued that the tendency to perceive an electoral outcome as foreseeable is positively and consistently associated with satisfaction with the outcome. Across all studies, satisfaction with the outcome was significantly and positively associated with retrospective foreseeability, above and beyond voters’ preference for a “winning” or “losing” party. In Study 3, a measure of memory distortion of pre-electoral forecasts was included, which was only weakly associated with retrospective foreseeability, but not with satisfaction for the outcome, supporting the notion of different levels of hindsight bias associated with different cognitive and motivational factors.

It has been suggested that inequalities in personality are implicated in the intergenerational transmission of inequality

Inequality in personality over the life cycle. Miriam Gensowski, Mette Gørtz, Stefanie Schurer. Journal of Economic Behavior & Organization, Volume 184, April 2021, Pages 46-77. https://doi.org/10.1016/j.jebo.2021.01.018

Rolf Degen's take: Personality traits are similarly unequally distributed as wealth, and the former could be a cause of the latter

Chart: Steve Stewart-Williams (@SteveStuWill)

Abstract: We document gender and socioeconomic inequalities in personality over the life cycle (age 18–75), using the Big Five 2 (BFI-2) inventory linked to administrative data on a large Danish population. We estimate life-cycle profiles non-parametrically and adjust for cohort and sample-selection effects. We find that: (1) Women of all ages score more highly than men on all personality traits, including three that are positively associated with wages; (2) High-education groups score more favorably on Openness to Experience, Extraversion, Agreeableness, and Neuroticism than low-education groups, while there is no socioeconomic inequality by Conscientiousness; (3) Over the life cycle, gender and socioeconomic gaps remain constant, with two exceptions: the gender and SES gaps in Openness to Experience widen, while gender differences in Neuroticism, a trait associated with worse outcomes, diminish with age. We discuss the implications of these findings in the context of gender wage gaps, household production models, and optimal taxation.

Keywords: InequalityPersonalityBig Five-2 InventoryLife cycle dynamicsGender disadvantageSocioeconomic disadvantage

Narcissism, Machiavellianism, and psychopathy are weakly associated to creativity; the strongest links are between the traits and scientific creativity

Creativity and the Dark Triad: A Meta-Analysis. Izabela Lebud, Bernadetta Figur, Maciej Karwowski. Journal of Research in Personality, March 21 2021, 104088. https://doi.org/10.1016/j.jrp.2021.104088

Highlights

• A meta-analysis of the links between creativity and the Dark Triad of personality.

• Significant, weak relations between creativity and narcissism and Machiavellianism.

• Dark Triad is mainly related to creativity when it was measured with self-report.

• The strongest links between Dark Triad traits and scientific creativity.

Abstract: This paper presents a meta-analysis of the relationships between creativity (creative potential, activities, and achievement) and the Dark Triad of personality: narcissism, Machiavellianism, and psychopathy. Multilevel meta-analytic models demonstrated a small but significant positive association between creativity and narcissism (r = .15 [.10, .29]) and Machiavellianism (r = .06 [.02, .09]), but not with psychopathy (r = .03 [-.02, .07]). Creativity measures (self-report-vs.-performance), aspects (self-perception, creative activity, creative abilities, creative achievements), and domains (general, art, science, and everyday creativity) moderated the links with the Dark Triad. We discuss the possible mechanism of associations between Dark Triad traits and creativity and highlight future research directions.

Keywords: The Dark Triadcreativitymeta-analysispersonality

Swearing/cursing and coprophenomena are prevalent in daily life; swearing makes up around 0.5% of the daily spoken content, however, the inter-individual variability is very high

Swearing and coprophenomena – a multidimensional approach. Asne Senberg et al. Neuroscience & Biobehavioral Reviews, March 20 2022. https://doi.org/10.1016/j.neubiorev.2021.03.016

Rolf Degen's take: https://twitter.com/DegenRolf/status/1373509898823217155

Highlights

• Swearing/cursing and coprophenomena are prevalent in daily life.

• We provide a multidimensional approach to systematize swearing and coprophenomena.

• We provide a theoretical framework reasons, targets, functions/effects and influencing factors for swearing and coprolalia.

Abstract: Swearing, cursing, expletives – all these terms are used to describe the utterance of taboo words. Studies show that swearing makes up around 0.5% of the daily spoken content, however, the inter-individual variability is very high. One kind of pathologic swearing is coprolalia in Tourette syndrome (TS), which describes the involuntary outburst of taboo words. Coprolalia occurs in approximately 20-30% of all patients with TS. This review compares swearing in healthy people and coprolalia in people with TS and is the first one to develop a multidimensional framework to account for both phenomena from a similar perspective. Different research findings are embedded in one theoretical framework consisting of reasons, targets, functions/effects and influencing factors for swearing and coprolalia. Furthermore, the very limited research investigating obscene gestures and copropraxia, compulsive obscene gestures, is summarized. New research questions and gaps are brought up for swearing, obscene gestures and coprophenomena.

Keywords: swearingcursingcoprolaliacoprophenomenaTourette Syndrome

Sex differences in early experience and the development of aggression in wild chimpanzees

Sex differences in early experience and the development of aggression in wild chimpanzees. Kris H. Sabbi et al. Proceedings of the National Academy of Sciences, March 23, 2021 118 (12) e2017144118; https://doi.org/10.1073/pnas.2017144118

Significance: Chimpanzees, human’s close evolutionary relatives, are a tractable model system for understanding how physical aggression can develop in the absence of gender socialization. Here we used 13 y of behavioral data and a targeted 3-y social development study to document clear sex differences in chimpanzees’ early aggressive experiences, supporting the possibility for social experience to shape sex-typed behavior in the absence of explicitly taught gender norms. However, as young males’ own aggressive behavior provoked aggressive responses from others, experiential differences were influenced by early-emerging behavioral differences that already resembled adult patterns. By demonstrating interactions between exposure to aggression and developing behavior, our results add an important perspective to long-standing debates over the origins of gender differences in human aggression.

Abstract: Sex differences in physical aggression occur across human cultures and are thought to be influenced by active sex role reinforcement. However, sex differences in aggression also exist in our close evolutionary relatives, chimpanzees, who do not engage in active teaching, but do exhibit long juvenile periods and complex social systems that allow differential experience to shape behavior. Here we ask whether early life exposure to aggression is sexually dimorphic in wild chimpanzees and, if so, whether other aspects of early sociality contribute to this difference. Using 13 y of all-occurrence aggression data collected from the Kanyawara community of chimpanzees (2005 to 2017), we determined that young male chimpanzees were victims of aggression more often than females by between 4 and 5 (i.e., early in juvenility). Combining long-term aggression data with data from a targeted study of social development (2015 to 2017), we found that two potential risk factors for aggression—time spent near adult males and time spent away from mothers—did not differ between young males and females. Instead, the major risk factor for receiving aggression was the amount of aggression that young chimpanzees displayed, which was higher for males than females throughout the juvenile period. In multivariate models, sex did not mediate this relationship, suggesting that other chimpanzees did not target young males specifically, but instead responded to individual behavior that differed by sex. Thus, social experience differed by sex even in the absence of explicit gender socialization, but experiential differences were shaped by early-emerging sex differences in behavior.

Keywords: aggressive developmentsocial developmentfission–fusionearly social experienceexposure to aggression

Development of aggression in wild chimpanzees: Social experience differed by sex even in the absence of explicit gender socialization, but experiential differences were shaped by early-emerging sex differences in behavior

Sympathy for the underdog: people are inclined to adopt the emotional perspective of powerless (versus powerful) others

Sympathy for the underdog: people are inclined to adopt the emotional perspective of powerless (versus powerful) others. François Quesque, Alexandre Foncelle, Elodie Barat, Eric Chabanat, Yves Rossetti & Jean-Baptiste Van der Henst. Cognition and Emotion, Mar 16 2021. https://doi.org/10.1080/02699931.2021.1902282

Abstract: Upon learning of the story of Cinderella, most people spontaneously adopt the emotional perspective of this helpless young woman rather than of her older sisters who oppress her. The present research examines whether this pattern reveals a general human tendency to empathise more with the emotions of individuals with low (versus high) power. Six experiments (N = 878) examined how power influences the focus of people’s emotional attributions. Participants were presented with situations in which one character exercised power over another one and had to resolve a referential ambiguity by considering the perspective of one or the other character. Results show that participants largely privileged the emotional states of the low-power character over those of the high-power character. This effect was observed with different types of stimuli (comics and video clips), with high- and low-power roles attributed to pairs of different genders (Experiments 1–4) or same gender (Experiments 5–6). Finally, the tendency persisted – though it was reduced – when participants adopted a less passive role with respect to the characters (Experiment 3) and when power occurred in a less despotic way (Experiment 6). Results are discussed with respect to social attention and sensitivity to fairness.

KEYWORDS: Perspective-takingemotionpowermentalisingreferential ambiguity

Spending on clothing is linked to more happiness among males (less happiness among females); spending less on alcohol is linked to less happiness; less luxury has only a limited relationship with happiness

Happiness and Consumption: A Research Synthesis Using an Online Finding Archive. Ruut Veenhoven et al. SAGE Open, March 19, 2021. https://doi.org/10.1177/2158244020986239

Abstract: There is a considerable amount of research on the effect of income on happiness, but only a limited number of studies have considered how the spending of income works out on one’s happiness. In this article, we take stock of the scattered findings on the relation between consumption and happiness. We cover 379 research findings observed in 99 empirical studies. We use a new method of research synthesis, in which research findings are first described in a comparable format and then entered in an online “findings archive” (World Database of Happiness). This technique allows a condensed presentation of the many research findings, while providing readers access to the full results through hyperlinks from the text. Our systematic review reveals some unexpected findings, but does not provide a conclusive answer to the question of what patterns of consumption provide the most happiness for what type of people. Suggestions for further research are provided.

Keywords: life satisfaction, consumption, informed choice, research synthesis, findings archive

Discussion

In this article, we explored a new strand of consumer research, using a novel presentation method of “link-facilitated research synthesis.” The aim was to see what patterns of consumption produce the most happiness for what kind of people. What have we learned?

What We Know Now

Consumption is related to happiness, at least some kinds of consumption are. Although most of the correlations are small and insignificant, we did see several substantive links. When interpreted as denoting a causal effect, some findings suggest that a “Calvinist” or conservative consumption style tends to foster happiness. This appears in the findings on spending on durables and education. The observed correlation between house ownership and happiness can also be seen as a fruit of solid spending. Yet, we also found links between experience consumption and happiness.

Contrary to claims by critics of consumerism, we did not find much evidence of consumption reducing happiness. Owning a car does not seem to lower happiness. Some counter-intuitive findings reported in section “Daily Expenses and Happiness” are (a) spending on clothing is associated with greater happiness among males, but with less happiness among females; (b) high expenditure on communication is associated with less happiness; (c) the expected negative correlation between health expenditure and happiness persists when self-rated health is controlled; (d) spending less on alcohol is associated with lower happiness levels; (e) less luxury has only a limited relationship with happiness. An unexpected finding reported is section “House Ownership and Happiness” was that home ownership is most related to happiness among people with poor mental health. A suggestive finding reported in section “Car ownership and happiness” was that driving an expensive car does not go with greater happiness. All this requires further research.

What We Do Not Know Yet

The available studies on consumption and happiness do not show to what extent the correlations between consumption and happiness stem from a causal effect of consumption on happiness; only in the case of house ownership, there is some causal evidence.

We are still largely in the dark about the relationship between happiness and the use of goods and services purchased, such as in the above-mentioned case of car ownership and happiness. This aspect of consumption is intertwined with wider lifestyle and time-use issues. We can learn more about consumption’s effects on happiness using the methods of multiple moment assessments, such as the experience sampling method (ESM) or day reconstruction method (DRM; see, for example, Burger et al., 2020 on the relationship between lottery play and happiness for a study that uses multiple moment assessment).

This review focuses on what the relationship between consumption and happiness is, which is what consumers need to know to make informed decisions. This information will be more convincing if they also understand why particular kinds of consumption add or detract from happiness. Such effects are likely to differ across products, people, and situations; some will involve different psychological processes, such as need gratification, social comparison, as well as identification. For that purpose, we need studies that focus on particular products and particular consumers, as is common practice in marketing research.

Why So Many Blank Spaces?

The number of research findings on consumption and happiness is small, in particular when compared with the large body of research literature on consumer satisfaction with products and services. Another striking observation is that the few available studies are not very sophisticated: Most of the findings are cross-sectional, the columns for longitudinal and experimental studies in the tables are largely empty and the tables with specifications also show many blank spaces. Why is this the case?

We follow Stanca and Veenhoven (2015) who note that one of the reasons seems to be theoretical short-sightedness. Many mainstream economists still equate consumption with happiness in general and consumer satisfaction in particular. These economists are unaware of the above noted difference between expected and experienced utility and do not see the difference between needs and wants, nor do they know that happiness depends more on meeting the former than the latter. (Veenhoven, 2009)

Another reason is in commercial self-interest. Producers are interested in selling their products in the first place. They spend a lot of money on marketing research to get a better picture of what consumers expect will make them happy and on advertisements to influence these expectations and link to their products. Whether these products actually add to a consumer’s happiness is not the producer’s prime concern. Although there is a considerable body of research on consumer’s experienced satisfaction with products and services, there is little research on the effect of using products on satisfaction with life, not even in sectors where wider life satisfaction is evidently at stake, such as in the case of life insurances or residential care. This lack of research is part of a wider market failure. As there is limited dependable information on the long-term consequences of big consumer purchases on happiness, this could explain why there is no market competition on happiness effects and hence no product development in this direction.

The market is unlikely to solve this problem; governments and consumer unions are in a better position to press for more research on the effects of consumption on happiness. Scientists can also make a difference by informing the public about what kinds of consumption are conducive to happiness.

Lines for Further Research

How can we further expand our current body of knowledge? We have learned that more cross-sectional studies will not provide much more information. Thus, the focus should be on longitudinal studies that allow a view on changes in happiness following changes in consumption. One way to obtain follow-up data is to insert questions on consumer choice in ongoing large-scale longitudinal studies in which happiness is measured, such as the Australian HILDA, the British “Understanding Society Survey” and the German Socio-Economic Panel (GSOEP).¹⁴ Another option is to add questions on happiness to ongoing follow-up studies on consumption. One can think here of longitudinal studies on broad consumer behavior or particular kinds of consumption, such as the U.S. National Consumer Panel¹⁵ or the Quebec Longitudinal Study on Nutrition and Aging.¹⁶

The most informative research will be experimental studies, in which consumption change is induced externally and subsequent effects on inner happiness are traced, such as in the above-mentioned examples of subsidized house ownership (Rohe & Stegman, 1994) and the natural experiment with compulsory health insurance (Keng & Wu, 2014).

Next to such descriptive studies on what effects consumption exerts on happiness; we need more research on how consumption affects happiness; in other words, we need to understand the causal mechanisms involved.

Adaptation of sperm whales to open-boat whalers: Captures dropped 58pct in a few years, it appears that whales swiftly learned effective defensive behaviour

Adaptation of sperm whales to open-boat whalers: rapid social learning on a large scale? Hal Whitehead, Tim D. Smith and Luke Rendell. The Royal Society Biology Letters, Volume 17, Issue 3, Mar 17 2021. https://doi.org/10.1098/rsbl.2021.0030

Abstract: Animals can mitigate human threats, but how do they do this, and how fast can they adapt? Hunting sperm whales was a major nineteenth century industry. Analysis of data from digitized logbooks of American whalers in the North Pacific found that the rate at which whalers succeeded in harpooning (‘striking’) sighted whales fell by about 58% over the first few years of exploitation in a region. This decline cannot be explained by the earliest whalers being more competent, as their strike rates outside the North Pacific, where whaling had a longer history, were not elevated. The initial killing of particularly vulnerable individuals would not have produced the observed rapid decline in strike rate. It appears that whales swiftly learned effective defensive behaviour. Sperm whales live in kin-based social units. Our models show that social learning, in which naive social units, when confronted by whalers, learned defensive measures from grouped social units with experience, could lead to the documented rapid decline in strike rate. This rapid, large-scale adoption of new behaviour enlarges our concept of the spatio-temporal dynamics of non-human culture.

4. Discussion

While a combination of H1–H3 might produce a steep decline in strike rate, social learning of defensive measures between social units (HX) is the best-supported explanation for the rapid decline in strike rate following the first sperm whale sighting within a region. The whalers themselves wrote of defensive methods that they believed the whales were adopting, including communicating danger within the social group, fleeing—especially upwind—or attacking the whalers [17,18] (figure 1). Deep dives would also have been effective. But, perhaps the most straightforward change would be for sperm whales to cease their characteristic defensive behaviour against their most serious previous predator, the killer whale, Orcinus orca. Gathering in slow-moving groups at the surface and fighting back with jaws or flukes often works against killer whales [19,20], but will have only assisted the relatively slow-moving, surface-limited, harpoon-bearing open-boat whalers.

There are other behavioural changes that the whales may have made in response to whaling, but their impact on strike rates is less clear. There is some evidence that sperm whales formed larger groups in response to whaling [15], but this would likely have increased rather than decreased strike rates. They may have learned to avoid the whalers before the whalers detected them, but this should generally have reduced the mean detection range of the whalers and so increased the strike rate. However, if whales fleeing at long ranges made themselves more visible by blowing hard and showing their bodies forcefully, so increasing the number of sightings with groups that were not easily struck, this might have additionally decreased the strike rate.

Thus, there are learned behavioural changes that the sperm whales could have made to reduce strike rates, and some anecdotal witness that they did so. However, learning as individuals or within social units is not supported as the sole cause of the initial decline in strike rate. To achieve the observed reduction in strike rate through behavioural change, some mechanism must have allowed naive whales without the experience of whalers to receive the benefits of experience.

We suggest that naive social units learned defensive measures from grouped experienced social units and adopted them. Encounters with whalers typically lasted hours, and sperm whales through their echolocation and communication systems can probably sense and coordinate behaviour over ranges of several kilometres. Other processes could have enhanced the social learning process. If groups were particularly likely to split between or within social units after an experience with whalers, and then to join other units, this will have increased the probability that a naive animal was grouped with an experienced individual during its first encounter with whalers.

Our analysis provides substantial support for rapid (less than 20% generation time, so much too fast for genetic evolution) social learning over large spatial scales. The ability of sperm whales, or potentially other species, to rapidly change behaviour in the face of a new anthropogenic threat by making use of social learning has implications for the population significance of new threats, and their assessment. Data from the earliest exposures may not generalize to later periods, and vice versa.

Increased subjective age (personal aging rate perception) increases mortality very much; biggest factors in SubjAge are physical health and expections of sex life in 10 years

PsychoAge and SubjAge: development of deep markers of psychological and subjective age using artificial intelligence. Alex Zhavoronkov et al. Aging, Volume 12, Issue 23 pp 23548—23577, December 8, 2020. https://doi.org/10.18632/aging.202344

Rolf Degen's take: Higher subjective age doubles mortality risk, and one of the top concomitants of subjective age is how satisfying people expect their sex life to be in 10 years’ time

Abstract

Aging clocks that accurately predict human age based on various biodata types are among the most important recent advances in biogerontology. Since 2016 multiple deep learning solutions have been created to interpret facial photos, omics data, and clinical blood parameters in the context of aging. Some of them have been patented to be used in commercial settings. However, psychological changes occurring throughout the human lifespan have been overlooked in the field of “deep aging clocks”.

In this paper, we present two deep learning predictors trained on social and behavioral data from Midlife in the United States (MIDUS) study: (a) PsychoAge, which predicts chronological age, and (b) SubjAge, which describes personal aging rate perception. Using 50 distinct features from the MIDUS dataset these models have achieved a mean absolute error of 6.7 years for chronological age and 7.3 years for subjective age. We also show that both PsychoAge and SubjAge are predictive of all-cause mortality risk, with SubjAge being a more significant risk factor.

Both clocks contain actionable features that can be modified using social and behavioral interventions, which enables a variety of aging-related psychology experiment designs. The features used in these clocks are interpretable by human experts and may prove to be useful in shifting personal perception of aging towards a mindset that promotes productive and healthy behaviors.

Discussion

In this article, we present two novel aging clocks created within the deep learning paradigm — PsychoAge and SubjAge. Both these clocks use the same set of 50 psychosocial features to estimate human chronological age and subjective age, respectively. These clocks showed superior performance during CV in MIDUS 1 (MAEPsychoAge= 6.70 years; MAESubjAge= 7.32 years) and were verified in two other large data sets — MIDUS 2 and MIDUS Refresher (Table 1). In terms of epsilon accuracy, PsychoAge reached a score of 0.78 in MIDUS 1, and SubjAge — 0.74.

Having trained and verified the final models, we aimed to understand how PsychoAge and SubjAge see human aging and what features they pay the most attention to. With a tandem PFI-DFS approach we ranked all features according to their relative importance. Top-5 important features in both clocks were associated with health conditions (e.g. headache frequency) and relationship status (marital status, expectations from sex life in 10 years). Less significant features greatly differ in their relative importance for SubjAge and PsychoAge predictions. For example, top-20 PsychoAge features contain only one personality trait — neuroticism. Meanwhile, the only personality traits encountered among top-20 SubjAge features are — extraversion and openness.

These three personality traits, along with conscientiousness and agreeableness form “the big five traits”, which are commonly used in practice and scientific research to describe the human mental state landscape. High neuroticism is characteristic of emotional instability and common mental disorders, such as mood disorders, anxiety, and substance use disorders. Openness and extraversion, on the other hand, are considered more balanced traits, although their abnormally low scores are also related to social phobia and agoraphobia [27]. Positive orientation, seeking warmth, social interaction, and emotional stability may play an important role in psychological aging.

We hypothesized that the human mind evolves throughout the lifespan, which results in some traits, beliefs, or priorities shifting — not always in unison or at the same speed. At certain life stages, career-related priorities may rise, while at others they may fade and be replaced by different priorities. These lifelong progressions of the psyche eventually get recognized by the neural networks we constructed to let them build an image of psychological aging.

This idea of human mind progression is described in much more detail in the review of SST by Laura Carstensen. SST suggests that younger people are more goal-oriented, interested to obtain new knowledge and skills, while older people tend to value emotionally meaningful goals more.

To identify the psychosocial features that change while a person advances from one age group to another we trained separate DNNs on MIDUS 1 samples from three age groups (25-39, 40-64, 65-75 years). First, we defined the psychological aging core — variables that remain highly important (top-25) across all age groups (Table 2). The core contained not only strictly psychological features, however. To illustrate, marital status, hypertension medication, headaches, and body mass index were among the seven core features required for accurate chronological age prediction. Interestingly, neuroticism score also belonged to the same psychological aging core, as well as seeing the community as a source of comfort. Psychological traits within the subjective aging core contained aspirations scale, extraversion, openness, positive reappraisal prevalence, and two career-related variables — effort put into work now and work expectations in 10 years. In contrast to the first psychological core, which contained few psychological traits, the subjective core consisted almost exclusively of psychological features.

This highlights an important distinction between aging per se (as judged by PsychoAge) and our perception of it (as judged by SubjAge): subjective aging is mostly dependent on internal causes.

We also explored the uniquely important features for each age group — features that emerged only in one top-25 set. Since these features were recognized as important only in these groups, it may be assumed that they shift the most markedly during the corresponding life periods. To illustrate, young adults were not the only age group who responded affirmatively to the statement “Forceful describes you well”, but rather many of these people went through a transformation that affected their forcefulness. Detecting such a change was essential for a predictor to accurately predict whether a person was at the beginning or the end of this phase of life.

On their own, DNNs are unable to tell generational and age-related changes apart or tell the difference between pro-longevity and progeroid features. Thus, the results of the feature importance analysis should always be cautiously inspected and verified in more rigorous settings. Still, feature importance analysis is a powerful tool for hypothesis generation and the verification of overall biological relevance.

While neuroticism was identified as a part of the psychological aging core, it was also a uniquely important subjective aging feature in the elderly MIDUS 1 subsample. This may be interpreted as neuroticism progressing unnoticed by an individual until old age when it starts to affect the perception of age. Previous studies identified that neuroticism tends to cause low emotional differentiation, anxiety, and depression in old people [28, 29].

Other personality traits rendered important for subjective age estimation in the elderly were optimism, being outgoing, and content with life in general. These results indicate that these might be top-priority features to focus on while developing policies aimed to involve the elderly in social life. Several studies have shown the importance of a social and productive lifestyle during aging [30, 31]. psychologically important and active events may protect against aging diseases, such as dementia [32].

After establishing which variables are important in absolute terms, we aimed to measure the models’ response to changes in their values. Using mixed-effects linear models, we explored the monotonic trends between 50 variables, PsychoAge and SubjAge predictions (Supplementary Figure 1 and Supplementary Figure 2).

Once again, neuroticism showed unique behavior. Contrary to the other big five traits, neuroticism score was associated with higher SubjAge and lower PsychoAge. More specifically, people within the same PsychoAge group could have >5 years of SubjAge difference due to differences in neuroticism score alone. This verifies our previous conjecture that neuroticism is a key marker of subjective aging and may be used as a sensitive measure of emotional states and late-life depressive symptoms.

Other big five traits also had significantly large effects on both PsychoAge and SubjAge. For example, a person with the bottom openness score would feel 7.2 years older than their PsychoAge counterpart with the top score. In the meantime, a person with the bottom openness score would be 5.3 years younger, as measured by PsychoAge, than their SubjAge counterpart with the top score. Similar tendencies could be observed for most other personality traits, thus building a strong case for SST.

Interestingly, personal opinion on when middle age starts and ends was significantly associated with higher PsychoAge but does not affect SubjAge. We hypothesize that this is an indication of “time dilation” associated with aging. As people get older, they place “middle age” higher and higher, as if their lifetime dilates, while younger participants may have stereotypes about aging and place “middle age” lower. An excellent study on the topic of perception of age stereotypes and self-perception of aging has been written by Hummert [33].

Among the health-related features, the distinction between internal and external health locus of control is of utmost interest. Health locus of control is a set of personal beliefs and experiences that determine whether a person takes responsibility for their health (internal locus) or considers it to be outside of their power, fully dependent on external factors (external locus). Internal locus of control is associated with a problem-solving mindset, while external locus is tied to depression, anxiety, and suicidal thoughts, as well as maladaptive behaviors [34]. We demonstrated that external locus of health control is a rare feature that demonstrated a linearly positive effect on both PsychoAge and SubjAge. It was the only feature to offer no payoff in at least one aging dimension, except for “Taking prescription medications for blood pressure”. Internal control, per contra, did not display concordant linearly negative effect on. Instead, it decreased SubjAge and decreased PsychoAge, just as most other health-related variables.

While the external locus of control was a senopositive (higher values increase age predictions) feature in both aging dimensions, some features were identified as double senonegative (higher values decrease age predictions). Increasing values for the variables from the relationships category were associated with lower PsychoAge and SubjAge, thus favoring single people content with their sex life, who expected to remain sexually active in 10 years. In this case, it is difficult to conclude the cause-effect relation between psychological aging and sexuality. Is reduced libido a precondition to becoming subjectively old? Or does feeling old due to other factors make people less interested in the sexual aspect of life? Can more satisfying sex life prolong healthy longevity, or does PsychoAge simply see higher sex drive as a feature more frequently encounter in the youth? More thorough research is required to answer these questions as well as similar questions concerning other variables.

Although the effect of most variables on PsychoAge and SubjAge was shown to be discordant, the magnitude of their effects on these two measures of psychological aging is not equal. Since the target variable in the mixed-effects model is expressed in years, Table 3 can be used to approximate how a shift in a psycho-social parameter will affect PsychoAge or SubjAge, and which one of them will change more. For example, the variable “Rate health in 10 years” is a survey question that measures health expectation on a scale from 0 to 10, from worst to best. Each increment increases PsychoAge by 0.5 years but also decreases SubjAge by 1.0 years. This yields an “exchange rate” of 2 subjective years lost per 1 chronological age gained. Other features have their own exchange rates, which may be manipulated to accumulate “net profit” in both SubjAge and PsychoAge dimensions.

Other directional feature analysis methods may be more appropriate for navigating the psychological aging landscape since linear mixed effect models operate based on multiple assumptions and simplifications. More specifically, they treat all features independently and approximate the complex interrelations between PsychoAge and SubjAge that may be in place with a random intercept. Accumulated local effects or more sophisticated Shapley value analysis may handle the convoluted feature interrelations more efficiently.

To further validate PsychoAge and SubjAge we tested their prediction errors (delta) as all-cause mortality risk factors (Figure 6). SubjAge delta was proven to be a more powerful risk factor than PsychoAge. More specifically, the SubjAge delta beyond ±5 years was associated with roughly doubling or halving the mortality rate.

We also tested the 50 psychosocial markers of aging as risk factors. We identified significant mortality risks associated with certain factors among (i) health features (“Health compared to others your age”, “Rate current health”, “Shortness of breath while walking up a slight hill”), (ii) personality traits (“Conscientiousness personality trait”, “Agency personality trait”), (iii) psychological beliefs (“Live for today”, “Positive reappraisal”, “Lower aspirations”), (iv) well-being (“Satisfied with life at present”), and, (v) demographic factors (“Chronological age”) (Figure 7).

A problem frequently encountered even by psychologists is obtaining sufficiently detailed information about their patients while keeping the data collection process as short as possible to avoid survey fatigue. In this work, we propose a solution to this survey length-descriptiveness balance problem based on modern deep learning and biogerontological methods. The solution is a relatively short list of features that are both modifiable and provably important in the context of aging.

Some studies show that family history is a source of numerous highly important aging-related features [35]. For example, having long-lived parents and grandparents is strongly correlated with a longer lifespan. However, such factors are not easily modified, especially if the grandparents are no longer alive. Therefore, in this study, we have deliberately limited questions on non-modifiable historical factors to give our surveys more practical value. We demonstrated that variables related to health and closer personal relationships play a crucial role in chronological and subjective age prediction. Furthermore, images about life changes, for instance, when females or males enter middle age, demonstrate a strong predictive power. We suggest that modifying the behavior and the mindset via these variables may be a promising therapeutic concept.

The factors comprising the developed aging clocks can be used to create individual behavioral therapies that would make them feel and actually become biologically younger. For example, PsychoAge can be used to quantify the beneficial effects of daily vigorous-intensity activity on their rate of aging. SubjAge, in its turn, can be used to quantify the beneficial effects of physical activity on personal perception of age.

Focusing on such modifiable age-related features while being able to score lifestyle choices numerically offers interesting opportunities to both professional therapists and individuals seeking self-improvement. We believe that the described approach has a high potential to increase longevity conscience on a population level.

When the category of close relationships is considered, people with access to PsychoAge and SubjAge may choose to develop stronger bonds, get married, or stay married out of an egoistic incentive to prolong their healthspan. The beneficial effect of close relationships and intimacy on health was previously shown in multiple studies, and we believe that drawing people’s attention to such physical-mental health connections should not be neglected [36].

Extracting actionable items from human biological profiles, such as transcriptomic or proteomic profiles, is an actively researched subject. The profiles associated with human psychology can also be subjected to similar workflows to devise personal behavioral therapy plans. In this study, we have demonstrated how the combination of deep learning and aging clocks can be used to create psychological surveys that promote longevity consciousness and personal improvement. These tools and methods could be applied in a wide range of research areas, including psychiatry, longevity, psychology, and psychophysiology for the greater good of society.

Inducing cognitive structure led novice consumers to experience numbness (less intense emotion); however, shifting experts away from using their cognitive structure restored their experience of emotion

Emotionally Numb: Expertise Dulls Consumer Experience. Matthew D Rocklage, Derek D Rucker, Loran F Nordgren. Journal of Consumer Research, ucab015, March 15 2021. https://doi.org/10.1093/jcr/ucab015

Abstract: Expertise provides numerous benefits. Experts process information more efficiently, remember information better, and often make better decisions. Consumers pursue expertise in domains they love and chase experiences that make them feel something. Yet, might becoming an expert carry a cost for these very feelings? Across more than 700,000 consumers and 6 million observations, developing expertise in a hedonic domain predicts consumers becoming more emotionally numb – i.e., having less intense emotion in response to their experiences. This numbness occurs across a range of domains – movies, photography, wine, and beer – and across diverse measures of emotion and expertise. It occurs in cross-sectional real-world data with certified experts, and in longitudinal real-world data that follows consumers over time and traces their emotional trajectories as they accrue expertise. Further, this numbness can be explained by the cognitive structure experts develop and apply within a domain. Experimentally inducing cognitive structure led novice consumers to experience greater numbness. However, shifting experts away from using their cognitive structure restored their experience of emotion. Thus, although consumers actively pursue expertise in domains that bring them pleasure, the present work is the first to show that this pursuit can come with a hedonic cost.

Keywords: expertise, emotion, hedonic, consumer knowledge, language, attitudes