Habitual well-digging in a rainforest-living group of East African chimpanzees, which may have been imported into the community’s behavioural repertoire by an immigrant female

Well-digging in a community of forest-living wild East African chimpanzees (Pan troglodytes schweinfurthii). Hella Péter, Klaus Zuberbühler & Catherine Hobaiter. Primates, Jun 6 2022. https://rd.springer.com/article/10.1007/s10329-022-00992-4

Abstract: Access to resources shapes species’ physiology and behaviour. Water is not typically considered a limiting resource for rainforest-living chimpanzees; however, several savannah and savannah-woodland communities show behavioural adaptations to limited water. Here, we provide a first report of habitual well-digging in a rainforest-living group of East African chimpanzees (Pan troglodytes schweinfurthii) and suggest that it may have been imported into the community’s behavioural repertoire by an immigrant female. We describe the presence and frequency of well-digging and related behaviour, and suggest that its subsequent spread in the group may have involved some degree of social learning. We highlight that subsurface water is a concealed resource, and that the limited spread of well-digging in the group may highlight the cognitive, rather than physical, challenges it presents in a rainforest environment.

Discussion

Chimpanzees living in water-restricted areas are able to exploit subsurface water by digging wells to access it (Nishida et al. 1999; McGrew et al. 2003; Hunt and McGrew 2002). Waibira chimpanzees were observed digging wells by hand next to a pool with stagnant surface water, their main water source during the dry season. We did not observe any use of tools for well-digging. Over a period of 377 days across seven annual dry seasons we documented habitual well-digging in four female chimpanzees. Importantly, this happened while stagnant surface water was available at the same time, suggesting they preferred the well water. Other individuals subsequently exploited the pre-dug wells for their own water access, either directly or by using sponges, again while (stagnant) surface water was available nearby.

Although digging behaviour (e.g. play digging) had been observed in the Waibira community prior to ONY’s immigration in 2015, we recorded no observations of well-digging in the community prior to 2015, despite camera trap video recording at the site (ongoing since January 2013) and direct observations during focal follows (ongoing since 2012). We also recorded no indirect evidence of well-digging at the water hole prior to 2015. While it is impossible to rule out that we missed this behaviour or failed to recognise the indirect traces of it, we consider it likely that ONY introduced the behaviour into the Waibira group. First, her competence and frequency of well-digging were remarkable from the beginning, suggesting that she knew the behaviour prior to immigration. Second, and equally remarkable, were the behavioural responses of other adult individuals who closely observed her well-digging behaviour and then exploited her wells over several years, suggesting that the behaviour was previously unknown to other Waibira adults.

A similar pattern was recorded in adult chimpanzees in Bossou, who closely observed (‘peering’) previously unknown nut-cracking behaviour in a field experiment (Biro et al. 2003). It has been argued that peering is a good indicator of ongoing social learning in apes (Schuppli et al. 2016), which is in line with our observations. Since its introduction in 2015, well-digging has now been observed repeatedly and in multiple individuals, suggesting it has spread–potentially by social learning–within the Waibira community. No similar behaviour has ever been observed in the well-studied neighbouring Sonso community (Reynolds 2005), despite three decades of careful observations and the fact that both groups occupy the same continuous forest habitat. Sonso chimpanzees, however, benefit from year-round access to a small river (the Sonso river), which flows across core areas of their territory and provides continuous access to fresh water.

Over the seven-season study period, we observed eight individuals to dig wells, but all four of the habitual well-diggers were females (three adults and one juvenile). While some younger males were observed to dig a well on at least one occasion, no adult male has so far been seen to dig one (although they were observed exploiting wells dug by others, suggesting a preference for the well water over the stagnant water that was still freely available). This female-biased pattern of spread is similar to that observed in Japanese macaques (Macaca fuscata) for potato washing (Nakamichi et al. 1998). Our camera trap coverage of the water hole is incomplete and it was not possible to observe all drinking events or social behaviours. Thus, it is likely that some well-digging and other digging-related behaviour were not captured in our video dataset. However, there is characteristic physical evidence of well-digging that is relatively easy to identify, such as the hole having clearly defined sides; the presence of separate marks made by fingers at the hole’s lip (where the fingers are initially dug into the soil) or in the area where the tailings remain; the presence of a small pile of substrate where the direction of digging with the fingers is consistent; in addition, the likelihood that well-digging has occurred is further supported by the presence of drinking tools in or around the hole (Video S4) (McGrew et al. 2007, 2013). During the same period of observation, the water hole and the surrounding area was surveyed regularly (at least once a week) for another study, and no indirect physical evidence of well-digging was observed prior to 2015. The failure to acquire this–very easily performed–behaviour by more individuals is puzzling, particularly since they have been observed to exploit the wells dug by other individuals. One possible explanation is that, while the physical act of well-digging for subsurface water is easy, the cognitive puzzle presented by its status as a concealed resource is more challenging, particularly given the (short) delay between the action of digging and the appearance of clean water, and the likely absence of clear cues to its presence. For example, in a muddy rainforest water hole olfactory cues to subsurface water presence are likely obscured by those from stagnant surface water. Delayed rewards or trace conditioning is shown to negatively impact the speed of learning compared to direct stimulus association (Kamin 1961; Beylin et al. 2001), and due to its significant cognitive demands, has been proposed as a possible test for animal consciousness (Shea and Heyes 2010). Additional reinforcing factors, such as observing a conspecific well-digging, may facilitate recognition of the connection between the action of manual digging and acquiring clean subsurface water.

Given wider trends in the spread and maintenance of group-specific behaviour in chimpanzees, we predict that in the future we will see (1) further spread of well-digging between adult females and immature individuals of both sexes; (2) matrilineal spread, as three of the habitual well-diggers were mature females, two of them with offspring; and (3) the possible spread to adult males with the maturation and rise in rank of immature male well-diggers.

In conclusion, we describe a new case of well-digging in chimpanzees–the first described for a rainforest-living group. We describe the apparent spread of this behaviour, which was potentially introduced by an immigrant female. The repeated innovation of well-digging across four communities of chimpanzees (McGrew et al. 2003, 2007; Hunt and McGrew 2002) could be explained by individual learning in response to a strong ecological necessity; however, the apparent absence of this behaviour in Waibira prior to ONY’s immigration, followed by its subsequent rapid acquisition by a few–but not many–group members, suggests that there was a socially mediated component to its spread in Waibira. Our observations support previous evidence suggesting that social transmission typically occurs to other younger or low or similarly ranked individuals (Horner et al. 2010). The now habitual use of a technique previously associated with communities that live in savannah or savannah-woodland highlights the importance of seasonal variation as well as broad ecological variation in resource availability for forest-dwelling chimpanzees (Wessling et al. 2018). Irrespective of the typical availability of water as a resource, the limited presence of water during at least some periods of the year appears sufficient to shape chimpanzee behaviour in the Waibira community. Taken together, these observations highlight both the striking variation and flexibility of chimpanzee behavioural repertoires.

We show that firms with more Machiavellian CEOs will have lower costs than other firms in the market, one reason why a personal characteristic that is usually seen as problematic for organizations is rather common in their upper ranks

Bargaining your way to success: The effect of Machiavellian chief executive officers on firm costs. Tessa Recendes, Federico Aime, Aaron D. Hill, Oleg V. Petrenko. Strategic Management Journal, March 27 2022. https://doi.org/10.1002/smj.3402

Research Summary: This study builds on insights from the upper echelons tradition in strategy to examine the effects of chief executive officer (CEO) Machiavellianism on relevant firm costs. While Machiavellianism has been usually construed as a purely negative trait, we argue that the pragmatic focus on the outcomes of exchanges and psychological obsession with winning in transactions that Machiavellian CEOs infuse in their organizations can have important effects on firm cost, a fundamental but frequently understudied driver of financial performance in strategic management research. In line with our arguments, we find that CEO Machiavellianism has negative effects on production costs, financing costs, and acquisition premiums. We find support for our ideas with a sample of S&P 500 CEOs, operationalizing CEO Machiavellianism using a videometric approach.

Managerial Summary: In this study, we investigate the effect of CEO Machiavellianism on firms’ costs. We show that firms with more Machiavellian CEOs will have lower costs than other firms in the market. Rather counterintuitively, this study suggests an explanation for why a personal characteristic that is usually seen as problematic for organizations is rather common in their upper ranks. Ultimately, the study demonstrates the value of the bargaining attitude that Machiavellian CEOs bring to their organizations and suggests this value should be weighed against their risks or acknowledged to manage the risks this common personal characteristic implies.

Spain & Portugal: Across a wide array of attitudes towards COVID-19, women were more likely to hold stronger, wider, and more cautionary attitudes about the virus

Opinions and options about COVID-19: Personality correlates and sex differences in two European countries. Sónia Brito-Costa, Peter Karl Jonason, Michele Tosi, Rui Antunes, Sofia Silva, Florêncio Castro. PLoS One, June 3, 2022. https://doi.org/10.1371/journal.pone.0268193

Abstract: In the initial months of the COVID-19 pandemic in 2020, we collected data (N = 1,420) from Portugal and Spain in relation to personality (i.e., Dark Triad traits, Big Five traits, religiousness, and negative affect) and attitudes related to COVID-19 about its origins, opinions on how to deal with it, and fear of it. The most pervasive patterns we found were: (1) neurotic-type dispositions were associated with stronger opinions about the origins of the virus and leave people to have more fear of the virus but also more trust in tested establishments to provide help. (2): religious people were less trusting of science, thought prayer was answer, and attributed the existence of the virus to an act of God. We also found that sex differences and country differences in attitudes towards COVID-19 were mediate by sex/country differences in personality traits like emotional stability, religiousness, and negative affect. For instance, women reported more fear of COVID-19 than men did, and this was verified by women’s greater tendency to have negative affect and low emotional stability relative to men. Results point to the central role of neuroticism in accounting for variance in broad-spectrum attitudes towards COVID-19.

Can Basic Education be Standardized? Evidence from Kenya

Gray-Lobe, Guthrie and Keats, Anthony and Kremer, Michael and Mbiti, Isaac and Ozier, Owen W., Can Education be Standardized? Evidence from Kenya (June 5, 2022). University of Chicago, Becker Friedman Institute for Economics Working Paper No. 2022-68. https://bfi.uchicago.edu/working-paper/2022-68/

Abstract: We examine the impact of enrolling in schools that employ a highly-standardized approach to education, using random variation from a large nationwide scholarship program. Bridge International Academies not only delivers highly detailed lesson guides to teachers using tablet computers, it also standardizes systems for daily teacher monitoring and feedback, school construction, and financial management. At the time of the study, Bridge operated over 400 private schools serving more than 100,000 pupils. It hired teachers with less formal education and experience than public school teachers, paid them less, and had more working hours per week. Enrolling at Bridge for two years increased test scores by 0.89 additional equivalent years of schooling (EYS) for primary school pupils and by 1.48 EYS for pre-primary pupils. These effects are in the 99th percentile of effects found for at-scale programs studied in a recent survey. Enrolling at Bridge reduced both dispersion in test scores and grade repetition. Test score results do not seem to be driven by rote memorization or by income effects of the scholarship.

The YouTube recommendation algorithm does push real users into mild ideological echo chambers, where users receive different recommendations distributions, but doesn't happen that many go down `rabbit holes' that lead them to extreme content

Brown, Megan and Bisbee, James and Lai, Angela and Bonneau, Richard and Nagler, Jonathan and Tucker, Joshua Aaron, Echo Chambers, Rabbit Holes, and Algorithmic Bias: How YouTube Recommends Content to Real Users (May 11, 2022). SSRN: http://dx.doi.org/10.2139/ssrn.4114905

Abstract: To what extent does the YouTube recommendation algorithm push users into echo chambers, ideologically biased content, or rabbit holes? Despite growing popular concern, recent work suggests that the recommendation algorithm is not pushing users into these echo chambers. However, existing research relies heavily on the use of anonymous data collection that does not account for the personalized nature of the recommendation algorithm. We asked a sample of real users to install a browser extension that downloaded the list of videos they were recommended. We instructed these users to start on an assigned video and then click through 20 sets of recommendations, capturing what they were being shown in real time as they used the platform logged into their real accounts. Using a novel method to estimate the ideology of a YouTube video, we demonstrate that the YouTube recommendation algorithm does, in fact, push real users into mild ideological echo chambers where, by the end of the data collection task, liberals and conservatives received different distributions of recommendations from each other, though this difference is small. While we find evidence that this difference increases the longer the user followed the recommendation algorithm, we do not find evidence that many go down `rabbit holes' that lead them to ideologically extreme content. Finally, we find that YouTube pushes all users, regardless of ideology, towards moderately conservative and an increasingly narrow range of ideological content the longer they follow YouTube's recommendations.

Keywords: YouTube, Recommendation Algorithms, Echo Chambers, Theory Testing

 

Liberals were more prone than conservatives to perceive a tweet with the opposing political view as a bot

Why Some Are Better than Others at Detecting Social Bots: Comparing Baseline Performance to Performance with Aids and Training. Ryan John Kenny. Carnegie Mellon University PhD Dissertations, May 2022. https://www.proquest.com/openview/a907b0780af36f04b33cb1477c8aadc9/1?pq-origsite=gscholar&cbl=18750&diss=y

Abstract: Social bots have infiltrated many social media platforms, sowing misinformation and disinformation. The harm caused by social bots depends on their ability to avoid detection by credibly impersonating human users. These three studies use a signal detection task to compare human detection of Twitter social bot personas with that of machine learning assessments. Across these studies, we find that sensitivity was (1a) minimal without training or aid, (1b) people were hesitant to respond ‘bot,’ and (1c) people were prone to “myside bias,” judging personas less critically when they shared political views. We also observed (1d) sensitivity improved when a bot detection aid was provided and (1e) when users received training focused on the objectives of social bot creators: to amplify narratives to an extensive social network. When participants labeled a persona a social bot, (2) the probability of their willingness to share its content dropped dramatically. We investigated the relationships between users’ attributes and social bot detection performance and found, (3a) social media experience did not improve detection and at times impaired it; (3b) myside bias affected the sensitivity and criterion used by liberals and conservatives differently; and (3c) analytical reasoning did not improve social bot detection, nor did it mitigate observed myside bias effects, but increased them slightly. We found that (4) people were more concerned about social bots influencing others’ online behaviors than being influenced themselves. Additionally, users’ willingness to pay for a social bot detection aid increased (5a) the more they were concerned about social bots, (5b) the greater their social media experience, (5c) the greater their sensitivity, and (5d) the higher their threshold for responding ‘bot.’ These findings demonstrate the threat posed by social  bots and two interventions that may reduce them.

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Political Values and Political Differences

As participants' political difference (PD) from the persona increased, they were more 

likely to judge it a 'bot,' consistent with myside bias, with a one standard deviation increase in 

PD shifting the intercept by 0.19. The post-hoc model adds participants' self-reported 

political values (PV) as the main effects and interactions. In the post hoc model, both liberal 

and conservative participants had a greater probability of responding ‘bot’ when viewing a 

persona of an opposing political view. However, liberals had a greater probability of 

responding ‘bot’ than conservatives. 

Both models' interaction between bot indicator and political differences (BI x PD) is 

explained by adding political values in the post-hoc model. The significant three-way 

interaction (BI x PV x PD) (p < 0.001) reveals an asymmetric pattern of sensitivity related to

participants’ political views. Figure 2 shows the relationship between PV and BI, with PD 

divided into five levels. In the upper left, when judging personas with similar political views,

liberals were very sensitive to the bot indicator score (red line), while conservatives were not

(purple line). At the other extreme, when judging personas with opposite political views, 

liberals were insensitive to bot indicator scores, while conservatives had a modest sensitivity.

Prenatal maternal stress: Pregnant women especially vulnerable to chronic stress; potential challenging situations such as body image issues, lifestyle changes, fluctuating hormones, induce lasting changes to fetal stress response ("fetal programming")

Prenatal stress perturbs fetal iron homeostasis in a sex specific manner. Peter Zimmermann, Marta C. Antonelli, Ritika Sharma, Alexander Müller, Camilla Zelgert, Bibiana Fabre, Natasha Wenzel, Hau-Tieng Wu, Martin G. Frasch & Silvia M. Lobmaier. Scientific Reports volume 12, Article number: 9341, Jun 4 2022. https://www.nature.com/articles/s41598-022-13633-z

Abstract: The adverse effects of maternal prenatal stress (PS) on child’s neurodevelopment warrant the establishment of biomarkers that enable early interventional therapeutic strategies. We performed a prospective matched double cohort study screening 2000 pregnant women in third trimester with Cohen Perceived Stress Scale-10 (PSS-10) questionnaire; 164 participants were recruited and classified as stressed and control group (SG, CG). Fetal cord blood iron parameters of 107 patients were measured at birth. Transabdominal electrocardiograms-based Fetal Stress Index (FSI) was derived. We investigated sex contribution to group differences and conducted causal inference analyses to assess the total effect of PS exposure on iron homeostasis using a directed acyclic graph (DAG) approach. Differences are reported for p < 0.05 unless noted otherwise. Transferrin saturation was lower in male stressed neonates. The minimum adjustment set of the DAG to estimate the total effect of PS exposure on fetal ferritin iron biomarkers consisted of maternal age and socioeconomic status: SG revealed a 15% decrease in fetal ferritin compared with CG. Mean FSI was higher among SG than among CG. FSI-based timely detection of fetuses affected by PS can support early individualized iron supplementation and neurodevelopmental follow-up to prevent long-term sequelae due to PS-exacerbated impairment of the iron homeostasis.

Discussion

PS disrupts fetal iron homeostasis in a sex-specific manner

This study indicates a sex-dependent difference in fetal iron homeostasis and FSI due to PS in an otherwise healthy cohort, mainly driven by the male sex. Causal inference approach allowed us to independently verify fetal sex as an important effect modifier on the causal pathway between PS and cord blood ferritin. The findings strengthen previous published FSI results10.

The PS effect on the fetal iron biomarkers has been poorly understood. Rhesus monkey infants born to stressed mothers were more likely to develop iron deficiency7. Likewise, several studies in humans have shown a correlation between PS and cord blood zinc protoporphyrin/heme index as well as PS and ferritin levels4,5,6.

During pregnancy, maternal stress hormones such as cortisol influence the growing fetus and its neurodevelopment, presumably via epigenetic mechanisms9,19. Cortes and colleagues proposed an influence of chronic stress through a stress-induced altered expression of a variant of the enzyme acetylcholinesterase on the iron-regulating system in fetal sheep brain-derived primary microglia cultures15. They assumed the afferent cholinergic anti-inflammatory pathway signaling on microglial α7 nicotinic acetylcholine receptors to down-regulate metal ion transporter and ferroportin, which acts as a hepcidin receptor (Fig. 1).

Animal studies observed stress-dependent cognitive deficits mainly seen in males20,21. In humans, sex-specific PS effects are reflected by lower scores in conduct assessments and higher test scores for emotional disturbance in males compared to females13,22,23. Campbell et al. applied six specific PS questionnaires, each twice in the second and third trimester, to 428 ~ 28-years-old mothers and found newborns of pregnant women exposed to violence to be stronger associated with cord blood ferritin levels lower in boys than in girls4.

The relation of iron homeostasis biomarkers to PS

Our results show no relationship between the presence of maternal anemia, fetal iron deficiency and PS. These findings are in agreement with literature suggesting that the fetus is robust against moderate changes of the maternal iron homeostasis24,25.

Within the DAG framework, we estimated that PS reduced the cord blood serum ferritin levels by approximately 15%. These findings are exceeding the adaption factor for inflammatory processes in infants the WHO uses in a current guideline26. We assume that during pregnancy even relatively small additional shifts in fetal iron homeostasis, especially in ferritin levels, may induce sex-specific neurodevelopmental effects27. Our observations regarding the link between PS, fetal iron homeostasis and the postnatal neurodevelopmental trajectories warrant further investigations, because this condition may be corrected therapeutically via targeted prenatal and/or postnatal iron supplementation2.

The PS effect transmitted by maternal cortisol on the fetal neurodevelopment may depend on the time course of exposure28,29. Hypothetically, taking our explanation further antepartum, i.e., to ~ 3.5 weeks earlier at the time of taECG recording, we speculate that PS-induced differences in hepcidin at that time may lead to the reported changes in iron parameters that could still be detected in the cord blood1. Our exploratory findings of higher FSI within certain ranges of at-birth iron biomarkers support this notion. The absence of group differences of cord blood iron parameters including the whole cohort may reflect adaptions (more pronounced in females) that occur as pregnancy progresses20.

The role of the immune system

Our data in leukocytes showed no evidence of increased inflammatory processes in SG neonates (Table S1). Nevertheless, acute inflammatory processes, a common phenomenon during delivery, may have had an effect on our cord blood findings transmitted by other cellular messengers such as the cytokine IL-6 (Fig. 1). In general, inflammation upregulates the acute phase protein ferritin influencing its role as a biomarker of the iron storage30. Inflammation also upregulates hepcidin levels leading to an intestinal sequestration of iron14. Cord blood interleukin levels were increased in chronically stressed mother’s infants31. Taken together, the effects of PS can be mediated by inflammatory processes and this link should be investigated further in future studies including a broader characterization of the maternal and neonatal inflammatory profiles32.

FSI as a potential biomarker of PS in late gestation

The present findings confirm that FSI is increased in PS during the third trimester of pregnancy10. Because the FSI showed poor association with the measured iron biomarkers, we assume that PS influences fHR and mHR coupling by different pathways. Moreover, in our DAG framework it is conceivable that FSI may serve as an indicator of subsequent altered neurodevelopmental trajectories, even in the absence of biochemical PS correlates such as alterations in iron homeostasis33,34.

ML-based predictions of PS

With our ML approach, we mimicked a real-life scenario to identify mother–fetus dyads affected by PS. Our results are consistent with findings in other clinical settings where electronic medical record mining identified patients at risk even without additional biophysical assessments, such as ECG35. Notably, adding biophysical characteristics improves ML model performance, thus emphasizing the potential of antepartum mother–child monitoring using taECG to improve the early detection of health abnormalities such as PS.

Strengths and limitations

Strengths of the FELICITy study are the prospective design preventing recall bias and the definition of criteria for a matching system to exclude possible confounders. Additionally, eventual confounding factors such as the intake of iron supplement and ethnic group showed no group differences (Fig. S1). This is the first prospective longitudinal study starting in utero aiming to assess PS and fetal biomarkers. Additionally, it is the first study to use causal inference and machine learning approaches to investigate sex-dependent influence of PS on the fetal iron homeostasis. There are certain limitations. Our inclusion criteria prevented us from enrolling non-German-speaking patients. This may have biased how the PS effects are represented in the multicultural Munich population. Also, we used a matching system that could not include every screened CG patient. Due to the uncertainties of a human study, several subject numbers for different sub-analyses were lower. Furthermore, we focused on measuring PS in the third trimester which necessarily neglected earlier stages of pregnancy and a possible temporal dynamic of PS over the entire course of pregnancy.

We chose not to include other potential effect modifiers on the causal pathway of the DAG such as inflammatory processes as they are difficult to define quantitatively and were not the focus of this study. However, future studies could further refine estimates of PS → Iron Biomarker average exposure effect by adjusting for these covariates.

This study did not differentiate between arterial or venous origin of the analyzed cord blood samples. To our knowledge this issue has not been addressed in literature so far. In general, the placental iron transfer and the assessment of the fetal iron status using cord blood parameters are poorly understood36,37. As of the date of the manuscript’s submission no commonly used normal ranges of cord blood iron parameters exist. The established ranges start with the child's birth26 but are not applicable to cord blood ranges since in cord blood usually, iron parameters are higher38. These issues warrant further research to identify potential biasing effects on cord blood analysis.

Maximizing men ("No matter what I do, I have the highest standards for myself") who had attractive wives more satisfied at start of their marriages; maximazing women who had high status husbands experienced less steep declines in satisfaction over time

Maximizing Tendencies in Marriage: Accentuating the Implications of Readily Observable Partner Characteristics for Intimates’ Satisfaction. Juliana E. French, Andrea L. Meltzer.Personality and Social Psychology Bulletin, March 5, 2019. https://doi.org/10.1177/0146167219832337

Abstract: People differ in their tendencies to labor over decisions and to make choices that maximize their outcomes—a difference known as maximization. Here, we used two independent, 3-year longitudinal studies of newlywed couples to demonstrate that this individual difference in decision making has important implications for romantic relationships. Consistent with the idea that maximizers are more likely to compare their current romantic partners to potential alternative partners’ readily observable qualities, such as their physical attractiveness and status, results demonstrated that intimates’ maximization moderated the implications of these sex-differentiated variables for marital satisfaction. Specifically, maximizing men who had attractive (vs. unattractive) wives were more satisfied at the start of their marriages. Likewise, maximizing women who had high (vs. low) status husbands experienced less steep declines in satisfaction over time. These findings demonstrate that maximization has important implications for long-term romantic relationships by accentuating the effects of readily observable partner qualities on relationship outcomes.

Keywords: maximizing tendencies, physical attractiveness, status, sex differences, marriage

Discussion

Rationale and Summary of Results

After choosing a long-term partner, intimates face a barrage of potential alternative partners. Given that maximizers (vs. satisficers) more frequently attend to such potential alternatives and compare the readily observable, desirable traits of those alternatives (e.g., physical attractiveness, status) to their current partners’ traits, they may be at greater risk of experiencing poorer relationship outcomes, to the extent that their partners compare less favorably to such alternatives. Nevertheless, if their partners compare more favorably to such alternatives, maximizers (vs. satisficers) may experience better relationship outcomes. Given the sex-differentiated preferences for partner physical attractiveness and partner status (e.g., Buss, 1989; Buss & Barnes, 1986; Kenrick et al., 1990; Li et al., 2002; Meltzer et al., 2014b; but also see Eastwick & Finkel, 2008), we predicted that maximizing men (vs. women) would be more satisfied to the extent that their partners are relatively attractive, and that maximizing women (vs. men) would be more satisfied to the extent that their partners have relatively high status. We pooled the data from two independent, 3-year longitudinal studies of newlywed couples to test these predictions. Results were consistent with predictions. Maximizing men (vs. women) were more satisfied at the start of their marriages to the extent that they had physically attractive partners; in contrast, satisficing men and women were no more or less satisfied at the start of their marriages to the extent that they had physically attractive partners. Likewise, maximizing women (vs. men) experienced less steep declines in marital satisfaction across the first three years of marriage to the extent that their partners had high incomes; in contrast, satisficing men and women experienced no more or less steep declines in marital satisfaction to the extent that their partners had high incomes. It is worth noting, however, that our higher order associations emerged as marginally (rather than traditionally) significant; results should thus be interpreted with caution until they can be replicated.

An astute reader may have noticed that maximizing women with attractive (vs. unattractive) partners were relatively less satisfied at the start of their marriages, and maximizing men with high (vs. low) status partners experienced relatively steeper declines in satisfaction over time. Although we did not predict such simple effects a priori, these findings are consistent with other research. Other scholars have demonstrated, for example, that women with attractive (vs. unattractive) partners are more concerned about sexual infidelity (White, 1980), which appears to be a valid concern—attractive, partnered men not only desire more frequent extra-pair relations (White, 1980), they engage in more frequent sexual infidelity (Gangestad & Thornhill, 1997; cf. Rhodes, Morley, & Simmons, 2013). Likewise, other scholars have demonstrated that increases in partnered women’s income leads to declines in their partners’ overall well-being over time (Rogers & DeBoer, 2001), and is associated with an increased likelihood of marital dissolution (Ono, 1998; Teachman, 2010). As the current work demonstrates, however, individual differences such as women’s maximizing tendencies can moderate these associations. Indeed, partner attractiveness was negatively associated with maximizing wives’ initial marital satisfaction but unassociated with satisficing wives’ initial marital satisfaction, and partner income was positively associated with maximizing husbands’ declines in marital satisfaction but unassociated with satisficing husbands’ declines in marital satisfaction.

Implications and Future Directions

These results have several important theoretical implications. Perhaps most notably, the current research demonstrates the critical implications of an important individual difference in decision-making styles for long-term romantic relationships—maximization. The choice of a long-term partner is a relatively enduring one that has notable implications for people’s overall physical and mental health (Holt-Lunstad et al., 2010; Proulx et al., 2007; Robles et al., 2014). For these reasons, decision making in this domain is critical; thus, it is likely that people attend to certain qualities in potential partners that will maximize their outcomes. Nevertheless, there are individual differences in such maximizing tendencies, and the current research provides novel evidence that such differences have implications for long-term relationship outcomes. Moreover, the current findings suggested that maximizers are not always successful in maximizing their outcomes. Indeed, maximizing men with unattractive partners were relatively dissatisfied with their marriages, and maximizing women with low-status partners experienced relatively steeper declines in marital satisfaction over time. These negative outcomes are likely due to maximizers’ tendencies to frequently attend to relationship alternatives (Mikkelson & Pauley, 2013). Although we were unable to directly test this mechanism in the current research, future research may benefit from doing so. Future research may also benefit from continuing to examine additional ways that maximization influences romantic relationships. For example, given men’s relative preference for sexual novelty (Little, DeBruine, & Jones, 2014), maximizing men (vs. women) may be at greater risk of lower sexual satisfaction in their long-term relationships, though this effect may be buffered by their partners’ willingness to introduce sexual novelty. Likewise, maximization may play an important role in individuals’ decision to marry such that maximizers may engage in longer courtships or be more hesitant to agree to marriage.

The current research also has implications for our understanding of maximization more generally. In contrast to most previous research demonstrating that maximizers (vs. satisficers) experience more negative outcomes following decision-making processes (Besharat et al., 2014; Bruine de Bruin et al., 2016; Newman et al., 2018), the current studies are among the first (at least to our knowledge) to demonstrate that some maximizers can actually experience more positive outcomes—especially in decision-making domains where an exhaustive search of all possibilities is impossible (Newman et al., 2018; Schwartz et al., 2002). Indeed, maximizing men were more satisfied to the extent that they had attractive partners, and maximizing women were more satisfied to the extent that they had high-status partners. Future research may benefit from further exploring other domains in which maximizers experience similar positive outcomes.

Readers familiar with the maximization literature may have noticed that, in the current research, maximization was, on average, unassociated with intimates’ initial satisfaction or changes in marital satisfaction (see the simple effects of maximization in Tables 2 and 3). Decisions regarding who to marry are critically important, and may be one of the most important decisions that people make in their lives. Given the enduring nature of such a decision, it is possible that newly married couples are less susceptible to such negative outcomes (at least at the beginning) because they may more heavily weigh the potential costs and benefits of their decision, and because they hold relatively positive illusions (Murray, Holmes, & Griffin, 1996). Indeed, we are unaware of other research that has examined the implications of maximization for such important life decisions. Although Mikkelson and Pauley (2013) demonstrated that maximizers (vs. satisficers) were less satisfied with their relationships, they utilized samples of undergraduate women, and the implications of choosing dating partners in young adulthood are notably less consequential than the implications of choosing marriage partners in adulthood. Of course, in the current research, the null association between intimates’ maximizing tendencies and their relationship outcomes were moderated by the quality of their partners.

The current findings also help reconcile inconsistencies in support for evolutionary-based theories such as sexual strategies theory (Buss & Schmitt, 1993) and parental investment theory (Trivers, 1972). According to such theories, partner attractiveness should more positively impact men’s (vs. women’s) long-term relationship outcomes, and partner status should more positively impact women’s (vs. men’s) long-term relationship outcomes. Although such effects have emerged in numerous studies (e.g., Li et al., 2013; Meltzer et al., 2014b), they have failed to emerge in other studies (Eastwick & Finkel, 2008; Eastwick et al., 2014). It is worth noting that the sex-differentiated effect of partner attractiveness trended toward significance in the current research, and the sex-differentiated effect of partner status emerged in the predicted direction. Nevertheless, both effects emerged more strongly for maximizers than for satisficers. It may thus be that unknown sample differences in maximization have accentuated sex differences in prior studies that demonstrated the predicted effect (e.g., Li et al., 2013; Meltzer et al., 2014b) and attenuated those differences in research that failed to demonstrate the predicted effect (e.g., Eastwick & Finkel, 2008, though see Meltzer et al., 2014a). Considering maximizing tendencies and other important individual differences in future research may provide more consistent results.

Finally, future research may benefit from considering the function of individual differences in maximizing tendencies—that is, why some people expend the time and energy necessary to labor over their decision making, such as choosing a suitable long-term partner, whereas other people do not. It may be that such individual differences reflect differences in individual needs, such as those stemming from different life histories. According to life history theory, the harshness and unpredictability of people’s childhood environments can affect their psychological and behavioral functioning in adulthood (e.g., Belsky, Steinberg, & Draper, 1991; Simpson, Griskevicius, Kuo, Sung, & Collins, 2012). People who are exposed to unpredictable early environments tend to be more opportunistic, be more impulsive, and are more likely to seek immediate gratification; thus, they may also be more likely to adopt satisficing tendencies when choosing a relationship partner. That is, they may be more likely to choose a “good enough” partner. People who are exposed to stable early environments, in contrast, tend to be long-term planners who delay gratification for later and potentially larger payoffs; thus, they may be more likely to adopt maximizing tendencies when choosing a relationship partner. That is, they may consider all possible partners in hopes of choosing the “best” partner. In other words, people’s maximizing tendencies may be a result of their early environmental exposure. Future research may benefit from examining this possibility, as well as whether early environmental experiences similarly moderate the effects of partner physical attractiveness and partner status on long-term relationship outcomes.

Strengths and Limitations

Several strengths of this research enhance our confidence in the findings reported here. First, the studies drew from, and did not vary across, two independent studies of marriage, which allowed for increased power. Second, in contrast to using newly formed or hypothetical relationships, the current study utilized samples of participants who were all young, married couples for whom the measured outcomes were real and consequential. Finally, analyses in the current study controlled numerous potential confounds (i.e., own attractiveness, own income, partner age, partner extraversion, and partner student status), helping to decrease the possibility that the results were spurious or suppressed due to associations with those variables. Nevertheless, supplemental analyses also demonstrated that the key effects continued to emerge in uncontrolled models.

Despite these strengths, several factors limit interpretations of the current findings until they can be replicated and extended. First, whereas the relative homogeneity of our two samples enhances our confidence in the pattern of associations that emerged, this lack of variability limits our ability to generalize these findings to other samples of couples (e.g., short-term couples, older married couples, nonheterosexual couples). Maximizing tendencies, for example, may similarly affect relatively shorter term relationships (e.g., dating relationships). Likewise, it is possible that maximizing tendencies may not moderate the association between partner attractiveness and relationship satisfaction among older couples. Given that the current predictions were derived from evolutionary perspectives and the notion that partner attractiveness is important to relationship outcomes due to its association with fertility and successful reproduction, partner attractiveness may no longer differentially affect older men’s and women’s long-term relationships (for a related discussion, see Meltzer et al., 2014a). Future research may benefit from examining this possibility and the extent to which the current findings generalize. Second, although we had a priori, theoretically driven predictions for two different traits that should matter for intimates’ relationship satisfaction in contextually different ways, the predicted effects emerged as marginally (rather than traditionally) significant. Nevertheless, there are notable challenges associated with conducting longitudinal, dyadic research (e.g., stringent inclusion criteria, resource intensiveness; see Finkel, Eastwick, & Reis, 2015) as well as known statistical difficulties of detecting moderator effects (McClelland & Judd, 1993); thus, we believe that the results reported here warrant notable consideration. Of course, future research would benefit from replicating the current results using a larger sample that is specifically designed to test these associations. Finally, the data presented here are correlational and thus are unable to support strong causal conclusions. Although we were able to control some variables that could have been responsible for the associations observed here, other potential third variables remained uncontrolled.