"Right-trunkers" and "left-trunkers": side preferences of trunk movements in wild Asian elephants (Elephas maximus)

In this article, the side preferences of feeding-related trunk movements of free-ranging Asian elephants (Elephas maximus) were investigated for the first time. It is hypothesized that a functional asymmetry of the trunk is necessary to perform skillful feeding movements more efficiently. This might be connected with a corresponding hemispheric specialization. Video recordings of 41 wild elephants provided frequencies and durations of the following trunk-movement categories: object contact, retrieval, and reaching. In each category, individual side preferences were found. The strength of side preferences varied between the trunk-movement categories and the sexes. Mean durations of retrieval and reaching correlated negatively with the strength of side biases. Comparing the side preferences in the unpaired trunk with analogous phenomena in other unpaired grasping organs and in primate handedness. the authors discuss possible explanations for the evolution of asymmetries in unpaired grasping organs.     

Prolactin and paternal care: comparison of three species of monogamous new world monkeys (Callicebus cupreus,Callithrix jacchus,and Callimico goeldii)

The authors explored whether prolactin is associated with paternal care in 3 monkey species: titi monkey (Callicebus cupreus), common marmoset (Callithrix jacchus), and Goeldi's monkey (Callimico goeldii). They compared prolactin levels in fathers before and after infant birth as well as between fathers and nonfathers. C. cupreus fathers carry infants almost exclusively, have higher prolactin levels than nonfathers, but show no prolactin increase after infant birth. C. goeldii fathers carry infants only after 3 weeks, show an increase in prolactin levels during the precarrying period, but do not have higher levels than nonfathers. C jacchus fathers are the primary carriers, have higher prolactin levels than nonfathers, and show a trend for a prolactin increase after the birth of infants. In conclusion, species differences in the patterns of prolactin secretion were evident and reflect the different paternal roles.     

Table of Contents of Volume 20

Volume Contents

Table of Contents of Volume 20     

Goal Imagery: Bridging the Gap Between Implicit Motives and Explicit Goals

Two studies examined the role of goal imagery (i.e., the perception-like mental representation of the pursuit and attainment of a goal) in establishing congruence between individuals' implicit motives and their inclination to pursue explicit goals assigned to them. Study 1 found that after a goal-imagery exercise, implicit needs for power and affiliation predicted participants' affective arousal and their commitment to a social-interaction goal furnished with power- and affiliation-related incentives. In Study 2, implicit power motivation predicted the level of performance participants achieved in pursuit of a competitive performance goal after a goal-imagery exercise. Without goal imagery, however, participants' motivation to pursue an explicit goal was independent of their implicit motive dispositions in both studies.     

Questioning the Virtual Friendship Debate: Fuzzy Analogical Arguments from Classification and Definition

Arguments from analogy are pervasive in everyday reasoning, mathematics, philosophy, and science. Informal logic studies everyday argumentation in ordinary language. A branch of fuzzy logic, approximate reasoning, seeks to model facets of everyday reasoning with vague concepts in ill-defined situations. Ways of combining the results from these fields will be suggested by introducing a new argumentation scheme—a fuzzy analogical argument from classification—with the associated critical questions. This will be motivated by a case study of analogical reasoning in the virtual friendship debate within information ethics. The virtual friendship debate is a disagreement over whether virtual friendships are genuine friendships. It will be argued that the debate could move away from its current impasse, caused by unproductive metaphysical and logical assumptions, if extant arguments are reinterpreted as fuzzy analogical arguments from classification, and subjected to a new set of critical questions which would replace the quest for facts of essence about friendship with an emphasis on empirical data, persuasion, and definitional power.     

Military training and personality trait development: does the military make the man, or does the man make the military?

Military experience is an important turning point in a person's life and, consequently, is associated with important life outcomes. Using a large longitudinal sample of German males, we examined whether personality traits played a role during this period. Results indicated that personality traits prospectively predicted the decision to enter the military. People lower in agreeableness, neuroticism, and openness to experience during high school were more likely to enter the military after graduation. In addition, military training was associated with changes in personality. Compared with a control group, military recruits had lower levels of agreeableness after training. These levels persisted 5 years after training, even after participants entered college or the labor market. This study is one of the first to identify life experiences associated with changes in personality traits. Moreover, our results suggest that military experiences may have a long-lasting influence on individual-level characteristics.     

Psychological correlates of violent and non-violent Hong Kong juvenile probationers

There is little known about Hong Kong juvenile offenders on probation. The purpose of this study was to compare Hong Kong juvenile violent with non-violent probationers on static demographic and psychological variables. The study comprised 109 male juvenile probationers aged 14-20 years (M = 16.97, SD = 1.44) in community transitional housing; 34 were adjudicated for violent offenses, while 75 were non-violent. The Rosenberg Self-Esteem Scale (RSES), Satisfaction with Life Scale (SWLS), Social Bonding Scale-Theft (SBS-T), Social Bonding Scale-Violent Crime (SBS-VC), Positive and Negative Affect Scales (PANAS), Impulsiveness Scale-Short Form (IS-SF) and CRIME-PICS II were administered to measure self-esteem, life satisfaction, social bond, positive and negative affect, impulsivity, pro-offending attitudes, and self-perceived life problems. Data on onset age of delinquent behavior, age of first adjudication, number of prior adjudications, and frequency of self-reported delinquency in the past year were also collected. t-tests were consistent with significant differences for violent offenders including higher self-esteem (p < 0.05). Non-violent offenders self-reported significantly more theft (p < 0.05) with a tendency to deny victim hurt more often (p < 0.01); 76.5% of violent offenders self-reported both violent and non-violent crime, while 58.7% of non-violent offenders reported only non-violent crime. For violent and non-violent offenders, the onset of delinquency was inversely related to the frequency of self-reported delinquency. Using ordinary least-squares (OLS) regression analyses, self-anticipated violent reoffending risk was predicted by age of onset, frequency of self-reported delinquency, social bond (inversely), and impulsivity, while non-violent reoffending risk was predicted by the number of prior convictions and self-reported delinquency. Only two psychological correlates, social bond and impulsivity, were related to violent delinquency; interventions are suggested.     

In competitive interaction displays of red increase actors' competitive approach and perceivers' withdrawal

Colors carry meaningful psychological signals. We hypothesized that the color red serves as a powerful cue in competition, affecting both actors and perceivers. Using simplified poker games we investigated the psychological meaning of color in competitive interaction, by examining how the color of chips (red vs. blue or white) used by participants or their competitors affected behavior. Although chip color was objectively unrelated to the chips' value or competitors' strength, perceiving competitors using red chips renders competitors more intimidating, which leads perceivers to withdraw. Furthermore, actors who used red chips felt more dominant, which led them to enhanced competitive approach. Displaying red thus makes actors feel stronger and increases competitive approach; perceivers of displays of red in competitors feel intimidated and withdraw from competing.