Both extraversion & agreeableness are positively associated with life satisfaction and this association is much stronger for extraversion; agreeableness can even be detrimental on life satisfaction

Agreeableness, extraversion and life satisfaction: Investigating the mediating roles of social inclusion and status. Filip Fors Connolly, Ingemar Johansson Sevä. Scandinavian Journal of Psychology, June 22 2021. https://doi.org/10.1111/sjop.12755

Abstract: We examine inclusion and status as potential mediators in the relationships between extraversion and agreeableness, on the one hand, and life satisfaction, on the other hand. Previous research has shown that agreeableness is less strongly related to life satisfaction compared to extraversion. We argue that the relatively weak association between agreeableness and life satisfaction is due to the fact that, even though this personality trait is positively related to inclusion, it is only weakly related to status. Using structural equation modeling (SEM) and survey data from Australia, Denmark and Sweden, we test five hypotheses about the linkages between these personality traits, inclusion, status and life satisfaction. Our results show that both extraversion and agreeableness are positively associated with life satisfaction and that this association is much stronger for extraversion. Furthermore, our results show that extraversion is reliably associated with both inclusion and status, whereas agreeableness is a reliable predictor of inclusion but not of status. Turning to our mediation analysis, our main results demonstrate that the relationship between extraversion and life satisfaction is fully mediated by both inclusion and status, whereas the relationship between agreeableness and life satisfaction is partially mediated by inclusion. Our mediation analysis further shows that agreeableness has a negative direct effect on life satisfaction over and above the positive indirect effect through inclusion. Our findings highlight the role of both inclusion and status as important mediators in the relationships between extraversion and agreeableness, on the one hand, and life satisfaction, on the other hand.

DISCUSSION

The purpose of this study was to increase knowledge about the role of both social inclusion and social status in explaining the relationships between the personality traits extraversion and agreeableness, on the one hand, and life satisfaction, on the other hand. Given that both inclusion and status constitute the social basis of life satisfaction, it is surprising that no previous studies have investigated the extent to which each of these social needs can explain the relationship between personality traits and life satisfaction. More specifically, it is notable that the role of social status largely has been neglected in the literature on subjective well-being until recently, and that no studies have examined the mediating role of status in the extraversion–life satisfaction relationship as well as in the agreeableness–life satisfaction relationship.

Turning to our main result, we expected that status should mediate the relationship between extraversion and life satisfaction over and above inclusion, and that inclusion but not status should mediate the relationship between agreeableness and life satisfaction. The results confirm our hypotheses in showing that the relationship between extraversion and life satisfaction is mediated by both status and inclusion, whereas the relationship between agreeableness and life satisfaction is primarily mediated by inclusion. In addition, we found a direct negative effect of agreeableness on life satisfaction over and above the indirect positive effect through inclusion. We thus contribute to previous research by showing that both status and inclusion are independently and positively related to life satisfaction, thereby confirming that the social basis of life satisfaction is constituted by both types of social rewards. We also replicated results from previous research in showing that extraversion displays a much stronger relationship to life satisfaction than agreeableness. Our study also adds to previous research by demonstrating that extraversion is reliably related to both inclusion and status, whereas agreeableness is only a reliable predictor of inclusion but not of status. Although previous studies have demonstrated similar relationships, our study contributes using a larger and more representative sample than most other studies (cf. Anderson et al., 2001; Mahadevan et al., 2019).

If high levels of life satisfaction depend on being both included and admired, traits that increase both of these needs will have a larger impact compared to traits that only fulfill one of these needs. Previous studies on the relationship between extraversion and life satisfaction have largely focused on measures related to inclusion as an important mediator. However, based on our findings, inclusion is only a partial mediator in this relationship, as status also plays an important role. The role of status is compatible with Smillie et al. (2015) and Sun et al. (2017), who found that social contribution is an important mediator in the extraversion-positive affect relationship. Since social contribution most likely is an important antecedent of status, we consider our results to be an extension of these studies on the role of extraversion, social contribution and positive affect. Nevertheless, we suggest that future studies should further assess the relative importance of social contribution and social status as mediators in the relationship between extraversion and life satisfaction.

Regarding inclusion, our findings showed that inclusion in the family domain was more strongly related to life satisfaction than inclusion in the domain of friends. This result mirrors previous studies, which have found that satisfaction with family is a stronger correlate of life satisfaction than satisfaction with friends (Tiefenbach & Kohlbacher, 2015). We also found that both agreeableness and extraversion were positively related to inclusion in the domain of family to a similar degree, but that extraversion was slightly more strongly related to inclusion when it comes to friends. This suggests that extraversion is at least as important as agreeableness in nurturing positive social relationships beyond its effect on social status.

When it comes to the negative direct association between agreeableness and life satisfaction observed in our mediation model, that is, when holding levels of inclusion constant, a more agreeable person tends to have lower levels of life satisfaction compared to a less agreeable person. Future studies should devote attention to explaining this negative association. We consider one possible explanation to be that individuals with high levels of agreeableness risk being exploited in social interactions (Hilbig, Glöckner & Zettler, 2014), which may negatively affect life satisfaction through reducing personal goal attainment.

We acknowledge the following potential limitations in our study. Since our analysis is cross-sectional, we cannot claim that the observed effects are causal, only that the results do not reject causal effects. However, since personality traits are highly stable over time (especially rank order stability) and partly inherited (McCrae, 2011; Specht, Egloff & Schmukle, 2011), it is reasonable to assume that personality traits mainly affect status and inclusion rather than the reverse. However, since some studies show that life events can affect personality traits (Scollon & Diener, 2006), reciprocal effects between status/inclusion and personality traits can certainly not be entirely ruled out. An important avenue for future research is, therefore, to investigate this issue using longitudinal data and/or experimental research designs.

Another potential limitation is that all our measures were based on self-reports. As a consequence, the strength of the associations between agreeableness, extraversion, inclusion, status and life satisfaction may be inflated due to common method bias (see Schimmack & Kim, 2020). However, even though the magnitude of these associations may be inflated in an absolute sense, the relative strength of these associations should still be reasonably accurate. For instance, even if the true association between extraversion and status is weaker than the one based on self-reports, the finding that extraversion is more strongly associated with status than agreeableness should still be valid.

Furthermore, even though we used large-scale survey data, in contrast to most previous studies on the relationship between personality and life satisfaction, our data were restricted to participants from Australia, Denmark and Sweden. Previous research provides some support for cross-cultural differences in terms of the associations between personality traits and life satisfaction. For instance, Kim et al. (2018) found that extraversion was a stronger predictor of life satisfaction in US samples compared to samples from the UK, Germany and Japan. It is conceivable that the cultural emphasis on social status attainment in American society might explain this pattern. Thus, future research should investigate whether the mediating role of status in the extraversion–life satisfaction relationship is stronger in the US compared to the countries analysed in this paper.

There could also be potential limitations associated with the measures used in our analysis, in particular regarding the measures of extraversion, agreeableness and inclusion. For example, the items used to capture inclusion were originally created for measuring loneliness and relationship satisfaction. However, since we were able to estimate an underlying latent factor using these items, we argue that this factor most likely captures the degree to which individuals are included in the domains of family and friends. When it comes to our personality measures, a limitation is that we used a relatively short scale with only four items for capturing extraversion and agreeableness, respectively. Consequently, our measures may not capture each trait in a fully balanced way. For instance, previous studies have shown that the mini-IPIP measure used to capture extraversion in this study relates more strongly to facets such as gregariousness and friendliness compared to assertiveness (Donnellan et al., 2006), which could have inflated the association between extraversion and life satisfaction somewhat. Future studies should, therefore, attempt to replicate our findings using more exhaustive measures of extraversion and agreeableness.

Finally, future research should also investigate to what extent status and inclusion mediates the relationship between extraversion, agreeableness and other forms of well-being such as psychological well-being (Ryff, 1989). It has previously been shown that personality traits are more strongly associated with it than with life satisfaction (Anglim et al., 2020; Kokko, Tolvanen & Pulkkinen, 2013). However, no studies have to our knowledge investigated how psychological well-being is related to social status. Another important avenue for future research is to investigate whether self-esteem acts as an additional mediator in the relationships analysed here. Mahadevan et al. (2019) recently showed that self-esteem tracks both inclusion and status. One could, therefore, expect that extraversion and agreeableness should affect inclusion/status, which in turn influence self-esteem and subsequently judgements of life satisfaction.

We highlight several important contributions of our study. First, while previous research on life satisfaction as well its relationship to personality has primarily focused on social inclusion, our study has shed light on the importance of social status for life satisfaction as well the role of status in the relationship between personality traits and life satisfaction. Second, our study also increases the understanding of why extraversion is more strongly related to life satisfaction than is agreeableness, by showing that both inclusion and status mediate the relationship between extraversion and life satisfaction, while the relationship between agreeableness and life satisfaction is primarily mediated by inclusion. Furthermore, we contribute by demonstrating that agreeableness is negatively associated with life satisfaction when taking the mediating role of inclusion into account. Our findings thereby suggest that pro-social motives and behaviors, which characterize high levels of agreeableness, may have only a weak effect on life satisfaction, since they do not necessarily lead to higher status. Moreover, high levels of agreeableness that do not lead to social inclusion may even be detrimental for life satisfaction. Third, while our study emphasizes the importance of social status for life satisfaction, it also points to a potential dilemma when thinking about how to promote life satisfaction and life satisfaction–enhancing behaviors. The pursuit of social status constitutes a zero-sum game, that is, one individual’s attainment of status will, by definition, lead to another individual’s loss of status. Therefore, promoting the status-enhancing effects of extraversion will not necessarily be beneficial for societal levels of life satisfaction and overall subjective well-being. Moreover, promoting agreeableness as well as the softer aspects of extraversion (warmth) should increase inclusion, which is beneficial for other people and society at large.

People high in hostile sexism especially likely to attribute negative outcomes to women who keep their last names after marriage; some effects especially strong among women judging other women

Functional perceptions of relational success and infidelity concerns for violators of gendered naming conventions in marriage. Kelsey Drea, Mitch Brown, Donald F. Sacco.  Journal of Social and Personal Relationships, June 16, 2021. https://doi.org/10.1177/02654075211025090

Abstract: Replicating and extending previous findings, we report two high-powered studies exploring how heterosexual men and women’s decisions to change or keep their surnames following marriage influence perceptions of various marital outcomes as a function of perceivers’ sexist attitudes. Participants in Study 1 evaluated men and women who indicated keeping or changing their surname after marriage, along with an articulated reason for their decision, specifically either to disrupt or reinforce gender norms. Study 2 removed the reasoning of their choice. Independent of participant gender or whether decision reasoning was provided, both studies demonstrated that targets who violated gendered naming norms (e.g., female keepers and male changers) were perceived more negatively than those who adhered to these norms (e.g., male keepers and female changers), particularly for participants higher in hostile sexism. We frame these findings from complementary evolutionary and sociocultural perspectives.

Keywords: Attitudes, gender norms, infidelity, marriage, sexism, surname

Laboratory: Moderate alcohol consumption unleashes homo economicus by inhibiting cooperation (due to a deterioration in mood and an increase in physiologic stress)

Zak PJ, Hayes K, Paulson E, Stringham E (2021) Alcohol unleashes homo economicus by inhibiting cooperation. PLoS ONE 16(6): e0253296, Jun 22 2021. https://doi.org/10.1371/journal.pone.0253296

Abstract: Human behavior lies somewhere between purely self-interested homo economicus and socially-motivated homo reciprocans. The factors that cause people to choose self-interest over costly cooperation can provide insights into human nature and are essential when designing institutions and policies that are meant to influence behavior. Alcohol consumption can shed light on the inflection point between selfish and selfless because it is commonly consumed and has global effects on the brain. The present study administered alcohol or placebo (N = 128), titrated to sex and weight, to examine its effect on cooperation in a standard task in experimental economics, the public goods game (PGG). Alcohol, compared to placebo, doubled the number of free-riders who contributed nothing to the public good and reduced average PGG contributions by 32% (p = .005). This generated 64% higher average profits in the PGG for those who consumed alcohol. The degree of intoxication, measured by blood alcohol concentration, linearly reduced PGG contributions (r = -0.18, p = .05). The reduction in cooperation was traced to a deterioration in mood and an increase in physiologic stress as measured by adrenocorticotropic hormone. Our findings indicate that moderate alcohol consumption inhibits the motivation to cooperate and that homo economicus is stressed and unhappy.

Discussion

We found that moderate alcohol consumption reduced contributions to a public good pool by 32%. Those who consumed alcohol earned 64% more money because they interacted with more cooperative placebo participants. Alcohol also doubled the number of participants who were complete free-riders, contributing nothing to the public good. BAC linearly reduced PGG contributions "unleashing" individuals to behave selfishly.

If money is the only value one receives from cooperation, at least as captured by the PGG, then the present study has shown that a moderate consumption of alcohol results in behavior closer to that predicted by traditional models in economics [2,18,72]. This may be due to alcohol’s stimulation of the neurotransmitter dopamine [38] that is strongly associated with reward-seeking behaviors [73]. Conversely, a rich literature has documented the humans are gregariously social and that most people in most circumstances are biased towards cooperation [74,75]. Our results are unlikely to be affected by the methodology we employed. Previous research has shown that monetary decisions that capture cooperative behaviors that include blood draws match those absent blood sampling [74]. Nevertheless, while we sought to capture typical social drinking, our results may not generalize to single-sex alcohol consumption or drinking by older cohorts.

Alcohol’s inhibition of appropriate social responses has been termed "alcohol myopia" [76] but is more typically seen in heavy drinkers and alcoholics that moderate imbibers [77]. The primary mechanism producing inhibition has been traced to an increase in the inhibitory neurotransmitter GABA [37]. If the treatment reported here resulted in alcohol myopia, it appeared to decrease the value put on social benefits and increase the value of selfish benefits as has been shown with testosterone administration [78]. Indeed, pre-play communication has been consistently been shown to increase cooperation [79], yet alcohol was shown to blunt this effect.

Alcohol’s reduction of the perceived value of cooperation was manifested in the present study by an increase in negative affect. Alcohol accentuates emotional volatility [76,80], negative affect [81], and impulsivity [82]. The reduction in prefrontal activity that moderates social-emotional responses [83] reduced affective states in alcohol-consuming participants and may have focused them on immediate monetary rewards rather than the psychic reward of conforming to a social norm of cooperation [84]. Most economics studies have measured impulsivity by the choice of immediate versus delayed rewards. Individuals showing patience for temporal rewards are generally more cooperative [85] counter to the results found here. The role of stress has not been measured in the existing literature and may explain the difference in findings. At the same time, trait impulsivity can lead to alcohol use and abuse [86].

Social rejection and physical pain have been also shown to increase one’s desire for money [87] and our analysis suggests that an increase in negative affect of moderate alcohol consumption may mimic pain responses when it comes to money [88]. This finding is in contrast to much of the literature showing that negative affect increases monetary allocations to others in ultimatum and dictator games [89]. We did not find that isolation while drinking influenced negative affect compared to those drinking socially as others have reported [90].

Perhaps our most valuable finding is that alcohol increases physiologic stress and through this route reduces cooperation. This was captured by higher levels of the stress hormone ACTH for those who consumed alcohol. ACTH, rather than cortisol, was measured because the former responds more quickly than the latter in line with the time course of the experiment. Moderate stress tends to increase prosociality [91–93] while high and/or chronic stress inhibits prosocial behaviors [94,95]. Moderate alcohol consumption may be an effective way to induce physiologic stress, in particular, by having people drink alone. Our finding that physiologic stress was higher for those drinking alone seems to be new in the literature that has focused on drinking to reduce stress [96]. While drinking alone is a known risk factor for alcohol abuse [90], we have shown that drinking alone reduces subsequent prosocial behaviors. This may further isolate and stress solo drinkers, influencing them to continue to imbibe alcohol. The increase in stress was primarily driven by women and we believe this finding is worth additional research. A replication of study’s results is warranted because when segmented into subsamples, some of the analysis was relatively underpowered.

Our findings show that homo economicus is alive and well and that alcohol is enough to bring him out. A variety of factors besides alcohol reduce prosocial tendencies, including high levels of testosterone and serotonin depletion [97]. The present study was not designed to capture the contribution of changes in neurotransmitters on cooperation, but this is a rich area for future research.

Both Google Search and Google Scholar more often than not ranked a link to the original article higher than a link indicating that the article has been retracted

The Dissemination of Scientific Fake News: On the Ranking of Retracted Articles in Google. Emmanuel Genot, Erik J Olsson. Jun 2021. Chapter in The Epistemology of Fake News. Oxford University Press (forthcoming Aug 2021, https://www.amazon.com/Epistemology-Fake-News-Engaging-Philosophy/dp/0198863977). https://www.lunduniversity.lu.se/lup/publication/c395d114-c3b2-486a-80a0-0c80c150adee

Summary: Fake news can originate from an ordinary person carelessly posting what turns out to be false information or from the intentional actions of fake news factory workers, but broadly speaking it can also originate from scientific fraud. In the latter case, the article can be retracted upon discovery of the fraud. A case study shows, however, that such fake science can be visible in Google even after the article was retracted, in fact more visible than the retraction notice. We hypothesize that the reason for this lies in the popularity-based logic governing Google, in particular its foundational PageRank algorithm, in conjunction with a psychological law which we refer to as the “law of retraction”: a retraction notice is typically taken to be less interesting and therefore less popular with internet users than the original content retracted. We conduct an empirical study drawing on records of articles retracted due to fraud (fabrication of data) in the Retraction Watch public database. The study tests the extent to which such retracted scientific articles are still highly ranked in Google –and more so than information about the retraction. We find, among other things, that both Google Search and Google Scholar more often than not ranked a link to the original article higher than a link indicating that the article has been retracted. Surprisingly, Google Scholar did not perform better in this regard than Google Search. We also found cases in which Google did not track the retraction of an article on the first result page at all. We conclude that both Google Search and Google Scholar runthe risk of disseminating fake science through their ranking algorithms.

“Ounce equivalents” of animal- and plant-based protein-rich foods may not be metabolically equivalent after all

Metabolic Evaluation of the Dietary Guidelines’ Ounce Equivalents of Protein Food Sources in Young Adults: A Randomized Controlled Trial. Sanghee Park, David D Church, Scott E Schutzler, Gohar Azhar, Il-Young Kim, Arny A Ferrando, Robert R Wolfe. The Journal of Nutrition, Volume 151, Issue 5, May 2021, Pages 1190–1196, https://doi.org/10.1093/jn/nxaa401

Abstract

Background: The Dietary Guidelines for Americans (DGAs) published an “ounce equivalents” recommendation to help consumers meet protein requirements with a variety of protein food sources. However, the metabolic equivalency of these varied protein food sources has not been established.

Objective: We have investigated the hypothesis that the anabolic responses to consumption of ounce equivalents of protein food sources would be directly related to the essential amino acid (EAA) content of the protein food source.

Methods: Following 3 d of dietary control, a total of 56 healthy young adults underwent an 8.5-h metabolic study using stable isotope tracer methodology. The changes from baseline following consumption of 1 of 7 different protein food sources were compared with the baseline value for that individual (n = 8 per group).

Results: Consumption of ounce equivalents of animal-based protein food sources (beef sirloin, pork loin, eggs) resulted in a greater gain in whole-body net protein balance above baseline than the ounce equivalents of plant-based protein food sources (tofu, kidney beans, peanut butter, mixed nuts; P < 0.01). The improvement in whole-body net protein balance was due to an increase in protein synthesis (P < 0.05) with all the animal protein sources, whereas the egg and pork groups also suppressed protein breakdown compared with the plant protein sources (P < 0.01). The magnitude of the whole-body net balance (anabolic) response was correlated with the EAA content of the protein food source (P < 0.001).

Conclusion: The “ounce equivalents” of protein food sources as expressed in the DGAs are not metabolically equivalent in young healthy individuals. The magnitude of anabolic response to dietary proteins should be considered as the DGAs develop approaches to establish healthy eating patterns.

Keywords: ounce equivalent, anabolic response, essential amino acids, net protein balance, stable isotope tracers

Popular version Not all dietary proteins are created equal (nutrition.org)

Laughter in response to tickling might express gender stereotypes of socio-expressive behavior in playful social interaction; involuntary muscle contractions may reflect biological components of playfulness in opposite gender constellations

The importance of skin area and gender in ticklishness. Sven Svebak. Scandinavian Journal of Psychology, June 21 2021. https://doi.org/10.1111/sjop.12756

Abstract: The importance of skin area and gender in ticklishness was explored in the present study. No previous report has been published on stimulation of the body surface exposed when dressed in a swimsuit (supine and prone positions), and the use of a feather has not been reported before. Fifty-seven university students volunteered (female N = 26, age range: 19–25, mean = 22.4; male N = 31, age range: 20–26, mean = 23.1). Sessions were videotaped for scoring of local involuntary muscle contractions (IMC) and laughter. Smiles were not scored because the face was not visible in the prone position. Subjective ticklishness was scored on a visual analogue scale. Areas that gave rise to ticklishness, were hatched onto a figure of the body. A two-factor design (gender of tickler by gender of ticklee) explored effects on dependent measures. Results showed that laughter was most frequent in female ticklees, disregarding the gender of the tickler. Subjective ticklishness and IMC scored high in opposite gender constellations. Ticklish areas included the ankles, knees, medial sides of the thighs and legs, lateral sides of the upper part of the body, elbows, the upper parts of arms, and the neck and shoulders. It was proposed that laughter in response to tickling stimulation might express gender stereotypes of socio-expressive behavior in playful social interaction, whereas IMC and subjective ticklishness may reflect biological components of playfulness in opposite gender constellations when tickled by a feather.

DISCUSSION

In general, the structure of the results supported the proposed distinction between the socio-expressive variable of laughter and the biological variables of IMC and subjective ticklishness. Laughter was more frequent in females than in males, whereas IMC scored high in opposite sex constellations, as did also the experience of the overall intensity of subjective ticklishness. It is stated in Table 2 that there was no relationship between the occurrence of IMC and laughter responses with the confounding variable of duration of the ticklish stimulation. The ANCOVAs for the IMC scores from the prone position also reflected a slightly less significant role for the gender of the tickler. It may be important to note that the significant ANCOVAs for the IMC occurred only for scores obtained in the prone (back) condition. It is possible that this type of skin stimulation relates somewhat to tickling in adult sex-related play behavior, as described in the book on erotic play by Moran (2003). However, this speculation should be left for empirical testing in the future. All subjects were within the same student population, and the laboratory may have facilitated the establishment of a protective mental frame (see Introduction) that has been proposed in reversal theory as important for the enjoyment of high arousal in the playful state and empirically supported later (see Svebak & Apter, 1987). The correlational analyses of the present findings support the validity of pleasure in the IMC where significant coefficients were calculated between laughter and IMC as well as between subjective ticklishness and IMC (Table 2). Moreover, the involuntary nature of the spontaneous IMC appeared to be similar to observations reported in previous electromyographic research that have supported a role for strong and phasic muscle responses (short-lasting, stimulus-elicited) during sensory-motor task performance in a playful mental state (Svebak, 1984).

The IMC response may be seen as a defensive evolutionary response where the aim is to rid the skin surface of an irritant by means of a local vibration. The IMC often triggers other defensive reactions as well, such as brushing and scratching of the stimulated area. Tickling most often is a pleasant sensory experience whereas itching may also involve pleasure when it is mild. However, both are mediated by the afferent pain system and, therefore, has been described as a pain-pleasure system (Mintz, 1967). In this way, laughter during ticklishness may be seen as a sociocultural signal of playfulness, whereas IMC as well as subjective ticklishness may be biological reflexes that express the paradox of mixed feelings in playfulness. Provine (2000, p. 120) discussed the social and biological complexity of the tickle stimulus and the related responses, and he pointed to the defensive movements often seen in the ticklee: “Ticklees may variously hit, kick, or wriggle to rid themselves of the stimulus.” All this may be accompanied by the contrasting behavior of hilarious laughter to encourage the tickler to continue. In this way, laughter seems to invite playful interaction whereas, at the same time, the IMC signals the opposite. The inherent paradox of ambiguity tends to increase felt arousal that is experienced as more and more pleasant with increasing arousal, provided the person is in a playful state. In contrast, it is felt as unpleasant worry or anxiety when in the serious state (Apter, 1992, 2007, 2018; Svebak & Apter, 1987).

The idea that tickle responses are signs of amusement has been discussed some years ago by Harris and Alvarado (2005), as based upon the association of smiling with humor. The relation with humor was not strongly supported in their study where smiling and laughing were also related to styles of coping with stimulation that may be experienced as slightly aversive. In general, humor, the sense of humor, laughter and smiling are all complex phenomena, and the sense of humor of an individual should not be confused with a biological trait of ticklishness. The present study did not investigate humor as a social phenomenon nor the sense of humor of the individual participant.

Recent techniques for the eliciting of ticklish responses, such as in the studies by Harris et al., appear to be more along with the gargalesis type when fingers are used, as opposed to the mild knismesis form which was used in the present study. Probably, the present study was open to playfulness because subjects were recruited on a voluntary basis, with no use of credit points that may facilitate a vicarious motive to participate, and with the use of a stimulation technique that is less invasive than is the use of fingers. In addition, the ticklers were introduced to the participants in a lecture beforehand. It is a fact that no subject asked to stop the stimulation despite the instruction to do so at any time if they felt for it.

It is often underlined that there are many different types of smiles as well as laughter. Smiles were not recorded in the present study, simply because the face was not visible in the prone position. Laughter was scored from video tapes by two independent judges who adopted a commonsense attitude toward scoring, with no further sophistication than to identify laughter as present or absent. The quality of the laughter was not scored. And a strong exhale would not be counted because it would not be accompanied by vocalization. This approach to scoring may have acted as a limitation and may explain why there were relatively few laughter reactions during the stimulation. The concordance between the two judges was almost perfect (see Method above). It is possible that important information about the distribution of responses may have been lost when facial expressiveness was not scored, and that an approach which made the face visible throughout the tickling procedure would have supported a different conclusion. However, the mapping of particularly ticklish areas all over the skin surface would not have been possible unless the subjects were stimulated also in the prone position where the face was invisible. This goal was seen as essential to the study.

The presence of a playful state during ticklishness could be validated by the use of a questionnaire at the end of the session. There are well established survey measures available to assess trait playfulness (Murgatroyd, Rushton, Apter & Ray, 1978; Svebak & Murgatroyd, 1985), but measures of state playfulness have proved to be much more difficult to validate and establish (Apter & Lewis, 2018; Desselles, Murphy & Theys, 2014). None were found to be useful in this experimental setting.

In the present study, mean scores on the subjective experience of ticklishness were slightly lover than those reported in an fMRI experiment by Carlsson, Petrovic, Skare, Petersson & Ingvar (2000) when using the same visual analog scale (66 as compared with 58 in the present experiment). This small difference may further validate the present method for eliciting ticklishness in the laboratory.

In conclusion, females appeared more often than males to respond overtly with laughter, disregarding the gender of the tickler, whereas IMC and subjective ticklishness appeared to be biological signals of play-related reflexive responses in opposite sex constellations. The precise subjective qualities of these responses should be further investigated in future research. The use of a feather for skin stimulation (knismesis: mild, soft) uncovered a complete list of locations that gave rise to the experience of ticklishness. The areas included the ankles, knees, medial sides of the thighs and legs, lateral sides of the upper part of the body, stomach, elbows, the upper part of arms, and the neck and shoulders. These areas may be different in gargalesis (vigorous, invasive) types of ticklish stimulation although they overlap well with the areas suggested by Hall and Allin (1897) based on a survey more than one hundred years ago.