More than just a pretty face? The relationship between immune function and perceived facial attractiveness.

It has long been hypothesized that attractiveness provides a cue to a target's health and immunocompetence. However, much of the research testing this hypothesis has relied on a small number of indirect proxies of immune function, and the results of this research have been mixed. Here, we build on this past research, examining the relationship between target attractiveness and (i) self-reported health, (ii) in vivo measures of inflammation and white blood cell count/composition, and (iii) in vitro tests of targets' immune function, including (c1) leucocyte proliferation in response to immunological stimulants, (c2) phagocytosis of Escherichia coli bioparticles, (c3) NK cell-mediated lysis of target tumour cells, and (c4) Staphylococcus aureus growth in isolated plasma. Results revealed multiple, sometimes sex-differentiated, relationships between targets' immune function and others' perceptions of their attractiveness. Together, this work suggests complex, often sex-differentiated relationships between immune function, health, and attractiveness.

Low Childhood Socioeconomic Status Promotes Eating in the Absence of Energy Need.

Life-history theory predicts that exposure to conditions typical of low socioeconomic status (SES) during childhood will calibrate development in ways that promote survival in harsh and unpredictable ecologies. Guided by this insight, the current research tested the hypothesis that low childhood SES will predict eating in the absence of energy need. Across three studies, we measured (Study 1) or manipulated (Studies 2 and 3) participants' energy need and gave them the opportunity to eat provided snacks. Participants also reported their SES during childhood and their current SES. Results revealed that people who grew up in high-SES environments regulated their food intake on the basis of their immediate energy need; they ate more when their need was high than when their need was low. This relationship was not observed among people who grew up in low-SES environments. These individuals consumed comparably high amounts of food when their current energy need was high and when it was low. Childhood SES may have a lasting impact on food regulation.

Tempting foods and the affordability axiom: Food cues change beliefs about the costs of healthy eating.

Many consumers report that healthy eating is more expensive than unhealthy eating (the affordability axiom). We hypothesize that endorsement of this belief may be driven by the motivation to eat unhealthy foods. We tested this hypothesis in three studies. Study 1 revealed that the affordability axiom is associated with poorer eating habits and higher Body Mass Index (BMI). Study 2 found that the presence of a tasty food cue in the environment increased endorsement of affordability axiom. Study 3 found that these effects were moderated by one's food intake goals. Food cues led non-dieters to increase endorsement of the affordability axiom, but had the opposite effect among those seeking to restrict their calorie intake. The affordability axiom might persist as a means of validating unhealthy food choices.

The effect of non-caloric sweeteners on cognition, choice, and post-consumption satisfaction.

Consumers often turn to non-caloric sweeteners (NCS) as a means of promoting a healthy body weight. However, several studies have now linked their long-term use to increased weight gain, raising the question of whether these products produce unintended psychological, physiological, or behavioral changes that have implications for weight management goals. In the following, we present the results of three experiments bearing on this issue, testing whether NCS-consumption influences how individuals think about and respond to food. Participants in each of our three experiments were randomly assigned to consume a sugar-sweetened beverage, an unsweetened beverage, or a beverage sweetened with NCS. We then measured their cognition (Experiment 1), product choice (Experiment 2), and subjective responses to a sugar-sweetened food (Experiment 3). Results revealed that consuming NCS-sweetened beverages influences psychological processes in ways that - over time - may increase calorie intake.

The Holy Father (and Mother)? Multiple Tests of the Hypothesis That Parenthood and Parental Care Motivation Lead to Greater Religiosity.

Parenting is a universal element of human life. However, the motivational and attitudinal implications of parenthood remain poorly understood. Given that many major religions prescribe parent-benefiting norms restricting sexual promiscuity and socially disruptive behavior, we hypothesized that both parenthood and parental care motivation would predict higher levels of religiosity. Studies 1 to 3 (N >2,100 U.S. MTurkers; two preregistered) revealed that parental status and motivation were robustly associated with religiosity in Americans, and that age-related increases in religiosity were mediated by parenthood. Study 4a (376 students) found a moderated experimental effect, such that emotionally engaged participants showed increases in religiosity in response to a childcare manipulation. Study 4b then replicated this effect in recoded data from Studies 1 and 2. Study 5 used data from the World Values Survey (N = 89,565) and found further evidence for a relationship between parenthood and religiosity. These findings support functional accounts of the relationship between parenthood and mainstream religiosity.

Too strong to care? Investigating the links between formidability, worldviews, and views on climate and disaster.

People vary in climate change skepticism and in their views on disaster cause and prevention. For example, the United States boasts higher rates of climate skepticism than other countries, especially among Republicans. Research into the individual differences that shape variation in climate-related beliefs represents an important opportunity for those seeking ways to mitigate climate change and climate-related disasters (e.g., floods). In this registered report, we proposed a study examining how individual difference in physical formidability, worldview, and affect relate to attitudes about disaster and climate change. We predicted that highly formidable men would tend to endorse social inequality, hold status quo defensive worldviews, report lower levels of empathy, and report attitudes that promote disaster risk accumulation via lesser support for social intervention. The results of an online study (Study 1) support the notion that men's self-perceived formidability is related to disaster and climate change beliefs in the predicted direction and that this relationship is mediated by hierarchical worldview and status quo defense but not empathy. An analysis of a preliminary sample for the in-lab study (Study 2) suggests that self-perceived formidability relates to disaster views, climate views, and status quo maintaining worldviews.

Sex differences in the impact of childhood socioeconomic status on immune function.

Early life stress increases one's risk for health problems later in life, and many studies find that these effects are sex-differentiated. Here, we examined relationships between multiple sources of early life stress and adult immune function in humans across several functional assays. Adult participants provided retrospective information about their childhood (a) socioeconomic status, (b) household unpredictability, and (c) exposure to adverse experiences. Participants' peripheral blood mononuclear cells (PBMCs) were then isolated for use in functional assays of immune performance: (a) tumor cell lysis by natural killer cells, (b) phagocytosis of Escherichia coli bioparticles, and (c) mitogen-induced leukocyte proliferation and cytokine release. In men, lower childhood socioeconomic status predicted decrements in immunological performance across functional assays, along with greater spontaneous cytokine release from PBMCs. These changes co-occurred with elevations in plasma testosterone levels. Similar effects were not observed for other sources of stress, nor were they found in women (with the exception of spontaneous cytokine release). These findings provide evidence that low childhood socioeconomic status has a lasting negative impact on multiple aspects of immune function, particularly in men.

No evidence for a relationship between MHC heterozygosity and life history strategy in a sample of North American undergraduates.

Although allelic diversity at the major histocompatibility complex (MHC) has implications for adaptive immunity, mate choice, and social signalling, how diversity at the MHC influences the calibration of life history strategies remains largely uninvestigated. The current study investigated whether greater MHC heterozygosity was associated with markers of slower life history strategies in a sample of 789 North American undergraduates. Contrary to preregistered predictions and to previously published findings, MHC heterozygosity was not related to any of the psychological life history-relevant variables measured (including short- vs. long-term sexual strategy, temporal discounting, the Arizona life history battery, past and current health, disgust sensitivity, and Big Five personality traits). Further, no meaningful effects emerged when analysing women and men separately. Possible reasons for why the current results are inconsistent with previous work are discussed.

PsychoBehavioroimmunology: Connecting the Behavioral Immune System to Its Physiological Foundations.

Although infectious disease has posed a significant and persistent threat to human survival and welfare throughout history, only recently have the psychological and behavioral implications of disease threat become a topic of research within the behavioral sciences. This growing body of work has revealed a suite of affective and cognitive processes that motivate the avoidance of disease-causing objects and situations-a cascade of processes loosely conceptualized as a "behavioral immune system (BIS)." Recent BIS research has linked disease threat to a surprisingly broad set of psychological and behavioral phenomena. However, research examining how the BIS is nested within our broader physiology is only beginning to emerge. Here, we review research that has begun to elucidate the physiological foundations of the BIS-at the levels of sensory modalities, cells, and genes. We also discuss the future of this work.

Inflammation Predicts Decision-Making Characterized by Impulsivity, Present Focus, and an Inability to Delay Gratification.

Here, we propose a novel theoretical model linking present-focused decision-making to the activities of the immune system. We tested our model by examining the relationship between inflammatory activity - in vivo and in vitro - and decision-making characterized by impulsivity, present focus, and an inability to delay gratification. Results support our model, revealing that inflammation predicts these outcomes even after controlling for factors that may contribute to a spurious linkage between them. Moreover, subsequent analyses revealed that our model was a better fit for the data than alternative models using present-focused decision-making and its health-harming behavioural sequelae (e.g., smoking, risky sexual behaviour) to predict inflammation, lending support for the proposed directionality of this relationship. Together, these results suggest that inflammation may contribute to decision-making patterns that can result in undesirable personal and societal outcomes.

Day length predicts investment in human immune function: Shorter days yield greater investment.

Winter is characterized by stressful conditions which compromise health and render animals more vulnerable to infection and illness than during other times of the year. Organisms are hypothesized to adapt to these seasonal stressors by increasing investment in immune function in response to diminished photoperiod duration. Here, we examined this hypothesis in a sample of healthy human participants. Using several functional immune assays in vitro, as well as by utilizing measures of in vivo proinflammatory cytokine levels, we predicted that shorter day length would be associated with greater investment in immunological function. Results revealed that shorter days predicted significant upregulation of several facets of immune function, including natural killer cell cytotoxicity, peripheral blood mononuclear cell proliferation (in response to, and in the absence of stimulation), and plasma levels of interleukin-6, as well as lower rates of Staphylococcus aureus growth in serum ex vivo. Further, consistent with the hypothesis that these trade-offs would be offset by decreased investment in mating effort, shorter day length also predicted lower levels of total testosterone in men. These results suggest that ambient photoperiod may be a powerful regulator of human immunological activity, providing some of the first evidence of seasonal changes in multiple facets of human immune function.

Behavioral immune system activity predicts downregulation of chronic basal inflammation.

Here, we present a mechanistically grounded theory detailing a novel function of the behavioral immune system (BIS), the psychological system that prompts pathogen avoidance behaviors. We propose that BIS activity allows the body to downregulate basal inflammation, preventing resultant oxidative damage to DNA and promoting longevity. Study 1 investigated the relationship between a trait measure of pathogen avoidance motivation and in vitro and in vivo proinflammatory cytokine production. Study 2 examined the relationship between this same predictor and DNA damage often associated with prolonged inflammation. Results revealed that greater trait pathogen avoidance motivation predicts a) lower levels of spontaneous (but not stimulated) proinflammatory cytokine release by peripheral blood mononuclear cells (PBMCs), b) lower plasma levels of the proinflammatory cytokine interleukin-6 (IL-6), and c) lower levels of oxidative DNA damage. Thus, the BIS may promote health by protecting the body from the deleterious effects of inflammation and oxidative stress.

A Method for Manipulating Blood Glucose and Measuring Resulting Changes in Cognitive Accessibility of Target Stimuli.

Much research in social psychology has investigated the impact of bodily energy need on cognition and decision-making. As such, blood glucose, the body's primary energy source, has been of special interest to researchers for years. Fluctuations in blood glucose have been linked to a variety of changes in cognitive and behavioral processes, such as self-control, political attitudes, and eating behavior. To help meet growing interest in the links between bodily energy need and these processes, this manuscript offers a simple methodology to experimentally manipulate blood glucose using a fasting procedure followed by administration of a sugar-sweetened, unsweetened, or artificially-sweetened beverage. This is followed by presentation of a method for measuring resulting changes in implicit cognition using a lexical decision-task. In this task, participants are asked to identify whether strings of letters are words or non-words and response latencies are recorded. Sample results from a recent publication are presented as an example of the applications for the experimental manipulation of blood glucose and the lexical decision task measures.

The impact of perceived disease threat on women's desire for novel dating and sexual partners: is variety the best medicine?

Researchers in the evolutionary sciences have long understood men's desire to mate with a variety of women. Because men's obligatory investment in offspring production is relatively small, men can directly increase their number of descendants by mating with multiple partners. Relatively less is known, however, about the conditions that favor sexual variety seeking in women. Drawing on insights from evolutionary biology and behavioral ecology, we examined the relationship between the perceived pathogen load in an environment and women's desire for sexual variety. Across 5 experiments, we primed women with cues indicating that the rate of disease is increasing in their environment. We then measured their desire for novel sexual and dating partners. Results revealed that women with a history of vulnerability to illness respond to these cues by desiring a greater number of novel partners. This shift was not found in men and did not predict variety seeking in a nonsexual domain. In addition to providing evidence of a novel conceptual link between the pathogen load and patterns of human mating behavior, this research also provides new insights into women's mating psychology and the conditions that favor sexual variety seeking in the greater investing sex.