Duchenne Smiles as Honest Signals of Chronic Positive Mood.

Chronic positive mood (CPM) has been shown to confer a wide variety of social, functional, and health benefits. Some researchers have argued that humans evolved to feel CPM, which explains why most people report better than neutral mood (the "positivity offset bias") and why particularly happy people have particularly good outcomes. Here, we argue that the Duchenne smile evolved as an honest signal of high levels of CPM, alerting others to the psychological fitness of the smiler. Duchenne smiles are honest because they express felt positive emotion, making it difficult for unhappy people to produce them. Duchenne smiles enable happy people to signal and cooperate with one another, boosting their advantages. In our literature review, we found (a) that not all Duchenne smiles are "honest," although producing them in the absence of positive emotion is difficult and often detectable, and (b) that the ability to produce and recognize Duchenne smiles may vary somewhat by a person's cultural origin. In the final section of the article, we consider behavioral influences on CPM, reviewing research showing that engaging in eudaimonic activity reliably produces CPM, as posited by the eudaimonic-activity model. This research suggests that frequent Duchenne smiling may ultimately signal eudaimonic personality as well as CPM.

Traits and trade-offs are insufficient for evolutionary personality psychology.

Comments on the article by D. Nettle, who has clearly shown that evolutionary psychologists need to focus more attention on individual differences, not just species-typical universals. Such differences are not mere "noise," and evolutionary theory will gain by understanding how they are produced and maintained. However, by focusing on personality traits and the five-factor personality model, Nettle left unaddressed many of the most important aspects of human personality. An evolutionary psychology of personality must ultimately explain not just trait differences but also differences in personal goals, values, motives, identities, and life narratives--essential elements of human individuality and functionality. K. M. Sheldon et al suggest four reasons why traits and the five-factor personality model do not provide an optimal approach for explaining the evolution of personality: (a) As constructs, traits provide little purchase for explaining the causes of behavior; (b) trait concepts do not acknowledge or explain people's variations around their own baselines, variations that are likely crucial for adaptation; (c) traits do not explain or even describe true human uniqueness, i.e. the ways in which a person is different from everybody else; and (d) traits do not explain personality from the inside, by considering what people are trying to do in their lives. In raising these issues Sheldon et al are suggesting that the important question for evolutionary personality study is not why people fall at different points on a continuum regarding traits x, y, and z, but rather why each person is inevitably unique while still sharing the same evolved psychology.

Fertility cycle patterns in motives for sexual behavior.

Three studies examined the relationship between fertility, as indexed by day in cycle or salivary estradiol levels, and reported motives for sexual intercourse. Data from university and community samples in both cross-sectional and repeated-measures designs showed that sex-for-intimacy motives are endorsed significantly less by women who are relatively more fertile or show higher salivary estrogen levels. Sex for enhancement, self-affirmation, and partner approval also declined, although the data were less consistent. The remaining motives (coping and power) showed no consistent patterns across fertility status. Results suggest that sexual motives are rooted partly in woman's biology and are discussed in terms of plausible evolutionary mechanisms that might promote female "choosiness" at midcycle.

Estrogen fluctuations, oral contraceptives and borderline personality.

Results from three studies suggest fluctuation in estrogen level may influence the expression of borderline personality disorder (BPD) symptoms. In the first study, 226 women were administered the Personality Assessment Inventory, borderline scales (PAI-BOR; L.C. Morey, The Personality Assessment Inventory, Professional Manual, 1991) and a questionnaire that assessed time in menstrual cycle and use of oral contraceptives, that is synthetic estrogens. BPD symptoms were most common in women using oral contraceptives and during times in the menstrual cycle when estrogen level is rising. In Study 2, 52 women were measured four times across one menstrual cycle and provided salivary samples at each test session. The samples were assayed and estrogen levels were obtained. The principle finding was that variation in estrogen levels predicted the presence of BPD symptoms (r=0.4, p<0.01). This relationship remained significant when a general increase in negative affect was statistically controlled. Study 3 employed a pre-post Oral Contraceptive (OC) design with a control group. It was found that for women with high pre-existing levels of BPD, symptoms became significantly worse after starting pill use (F (3,42)=4.7; p<0.01). Research findings that link the serotonin system and estrogen are reviewed and theoretical and practical implications are discussed.

Seventy years of research on personality and close relationships: substantive and methodological trends over time.

The present review is based on a quantitative analysis of the abstracts for 477 studies published since 1932 on the topic of personality and close (romantic) relationships. This approach enables a "bird's-eye" view of the content and methods that have characterized research in this area and an examination of publication trends over time. Results showed that 60% of all published studies in this area relied exclusively on cross-sectional and self-report methods; that nearly all used convenience samples, though more than half used nonstudent samples; and that more than one-third relied exclusively on data from individuals rather than couples. Few studies appeared to include elaborated networks of constructs in either the personality or relationship domain or to attempt to integrate an elaborated model of personality with an elaborated relationship model. Examination of trends over time revealed a mixed picture, with increasing use of the least informative designs balanced by evidence of increasingly complex conceptual models.