Does inequity aversion depend on a frustration effect? A test with capuchin monkeys (Cebus apella)

Brosnan and de Waal (Nature 425:297–299, 2003) reported that if a witness monkey saw a model monkey receive a high-value food, the witness was more inclined to reject a previously acceptable, but low-value food. Later work demonstrated that this alleged inequity aversion might be due to frustration induced by switching subjects from their role as models receiving a high-value food to the role of witnesses receiving a low-value food. In the present study, pairs of female capuchins exchanged a token for either a high- or a low-value food without switching their model–witness roles. Witnesses could exchange a token for a low-value food after an adjacent model had exchanged a token for the same food (Equity Condition) or for a high-value food (Inequity Condition). Failure- and latency-to-exchange measures showed that witnesses were unaffected by the food type offered to models (no inequity aversion). Moreover, models were unaffected by their history of food type offered (no frustration). These results join earlier work suggesting that alleged inequity effects depend on frustration-induction procedures. Furthermore, inequity effects sometimes fail to emerge because frustration induction in nonhuman primates is labile. This study complied with protocols approved by the Italian Health Ministry and all procedures were performed in full accordance with the European law on humane care and use of laboratory animals.     

Flexible cue use in food-caching birds

An animal’s memory may be limited in capacity, which may result in competition among available memory cues. If such competition exists, natural selection may favor prioritization of different memory cues based on cue reliability and on associated differences in the environment and life history. Food-caching birds store numerous food items and appear to rely on memory to retrieve caches. Previous studies suggested that caching species should always prioritize spatial cues over non-spatial cues when both are available, because non-spatial cues may be unreliable in a changing environment; however, it remains unclear whether non-spatial cues should always be ignored when spatial cues are available. We tested whether mountain chickadees (Poecile gambeli), a food-caching species, prioritize memory for spatial cues over color cues when relocating previously found food in an associative learning task. In training trials, birds were exposed to food in a feeder where both spatial location and color were associated. During subsequent unrewarded test trials, color was dissociated from spatial location. Chickadees showed a significant pattern of inspecting feeders associated with correct color first, prior to visiting correct spatial locations. Our findings argue against the hypothesis that the memory of spatial cues should always take priority over any non-spatial cues, including color cues, in food-caching species, because in our experiment mountain chickadees chose color over spatial cues. Our results thus suggest that caching species may be more flexible in cue use than previously thought, possibly dependent upon the environment and complexity of available cues.     

Who Discovered the Binary System and Arithmetic? Did Leibniz Plagiarize Caramuel?

Gottfried Wilhelm Leibniz (1646–1716) is the self-proclaimed inventor of the binary system and is considered as such by most historians of mathematics and/or mathematicians. Really though, we owe the groundwork of today’s computing not to Leibniz but to the Englishman Thomas Harriot and the Spaniard Juan Caramuel de Lobkowitz (1606–1682), whom Leibniz plagiarized. This plagiarism has been identified on the basis of several facts: Caramuel’s work on the binary system is earlier than Leibniz’s, Leibniz was acquainted—both directly and indirectly—with Caramuel’s work and Leibniz had a natural tendency to plagiarize scientific works.     

Psychosocial predictors of the short-term course and outcome of major depression: a longitudinal study of a nonclinical sample with recent-onset episodes

Three variables have been hypothesized to play important roles in prolonging the course of depressive episodes: a ruminative response style, significant interpersonal relationships, and childhood adversity. The authors examined whether these variables predicted the short-term course of major depressive disorder (MDD). Participants (n = 84) were college students with a recent-onset major depressive episode. Assessments included several interview and self-report measures, and data on interpersonal relationships were obtained from close confidants. Follow-up interviews were conducted 6 months later. After controlling for baseline severity, harsh discipline in childhood significantly predicted mean level of depression across the follow-up and level of depression at follow-up. Harsh discipline was also significantly associated with relapse but not with recovery. After controlling for baseline severity, rumination and the interpersonal variables did not predict the outcome of MDD.     

Rethinking speed theories of cognitive development. Increasing the rate of recall without affecting accuracy

Researchers have suggested that developmental improvements in immediate recall stem from increases in the speed of mental processes. However, that inference has depended on evidence from correlation, regression, and structural equation modeling. We provide counter-examples in two experiments in which the speed of spoken recall was manipulated. In one experiment, second-grade children and adults recalled lists of digits more quickly than usual when the lists were presented at a rapid rate of two items per second. In a second experiment, children received lists at a rate of one item per second; half the children were trained (successfully) to speak their responses more quickly than usual, at a rate similar to adults' usual rate. Recall accuracy was completely unaffected by either of these response-speed manipulations. Thus, although response rate is a strong marker of an individual's maturational level, it does not appear to determine the accuracy of immediate recall. These results have important methodological and theoretical implications for human development.     

The effect of caffeine on handwriting movements in skilled writers

In laboratory tasks, caffeine has been shown to improve psychomotor performance. The aim of the present experiment was to assess the effects of caffeine on a skilled everyday life task in habitual caffeine consumers. The assessment of handwriting movements of 20 adults was performed following the administration of 0mg/kg (placebo), 1.5mg/kg, 3.0mg/kg or 4.5mg/kg of caffeine. A digitising tablet was used for the assessment of fine motor movements. Participants were asked to perform a simple writing task. Kinematic analysis of handwriting movements showed that, in comparison to placebo administration, high doses of caffeine (i.e., 4.5mg/kg) can produce improvements in handwriting as indicated by more fluent handwriting movements as well as an increase in maximum velocity and maximum positive and negative accelerations. The results suggest that higher doses of caffeine can enhance psychomotor performance.     

The incremental validity of the MMPI-2: when does therapist access not enhance treatment outcome?

The present study examined whether therapist access to the Minnesota Multiphasic Personality Inventory (MMPI-2) predicted favorable treatment outcome, above and beyond other assessment measures. A manipulated assessment design was used, in which patients were randomly assigned either to a group in which therapists had access to their MMPI-2 data or to a group without therapist access to such information. Illness severity, improvement ratings, number of sessions attended, and premature termination were indicators of therapy outcome. Results indicated that therapist access to the MMPI-2 data did not add to the prediction of positive treatment outcome beyond that predicted by other measures in this setting. Findings from this initial study suggest that, compared with other resources, perhaps in clinical settings with an emphasis on diagnosis-based and evidence-based treatment, the MMPI-2 may not provide incrementally valid information. However, these effects warrant replication across different settings and samples. Guidelines for future studies are discussed.     

Incorporating if...then...personality signatures in person perception: beyond the person-situation dichotomy

Three studies investigated conditions in which perceivers view dispositions and situations as interactive, rather than independent, causal forces when making judgments about another's personality. Study 1 showed that perceivers associated 5 common trait terms (e.g., friendly and shy) with characteristic if...then... (if situation a, then the person does x, but if situation b, then the person does y) personality signatures. Study 2 demonstrated that perceivers used information about a target's stable if...then... signature to infer the target's motives and traits; dispositional judgments were mediated by inferences about the target's motivations. Study 3 tested whether perceivers draw on if...then... signatures when making judgments about Big Five trait dimensions. Together, the findings indicate that perceivers take account of person-situation interactions (reflected in if...then... signatures) in everyday explanations of social behavior and personality dispositions. Boundary conditions are also discussed.     

Stereotypes as dominant responses: on the "social facilitation" of prejudice in anticipated public contexts

This article challenges the highly intuitive assumption that prejudice should be less likely in public compared with private settings. It proposes that stereotypes may be conceptualized as a type of dominant response (C. L. Hull, 1943; R. B. Zajonc, 1965) whose expression may be enhanced in public settings, especially among individuals high in social anxiety. Support was found for this framework in an impression formation paradigm (Experiment 1) and in a speeded task designed to measure stereotypic errors in perceptual identification (Experiment 2). Use of the process dissociation procedure (B. K. Payne, L. L. Jacoby, & A. J. Lambert, in press) demonstrated that these effects were due to decreases in cognitive control rather than increases in stereotype accessibility. The findings highlight a heretofore unknown and ironic consequence of anticipated public settings: Warning people that others may be privy to their responses may actually increase prejudice among the very people who are most worried about doing the wrong thing in public.     

Universal sex differences in the desire for sexual variety: tests from 52 nations, 6 continents,and 13 islands

Evolutionary psychologists have hypothesized that men and women possess both long-term and short-term mating strategies, with men's short-term strategy differentially rooted in the desire for sexual variety. In this article, findings from a cross-cultural survey of 16,288 people across 10 major world regions (including North America, South America, Western Europe, Eastern Europe, Southern Europe, Middle East, Africa, Oceania, South/Southeast Asia, and East Asia) demonstrate that sex differences in the desire for sexual variety are culturally universal throughout these world regions. Sex differences were evident regardless of whether mean, median, distributional, or categorical indexes of sexual differentiation were evaluated. Sex differences were evident regardless of the measures used to evaluate them. Among contemporary theories of human mating, pluralistic approaches that hypothesize sex differences in the evolved design of short-term mating provide the most compelling account of these robust empirical findings.