Cooperative behavior of laboratory rats (Rattus norvegicus) in an instrumental task

Cooperation is a cognitively demanding, complex social behavior, found primarily in primates. Here we investigated mutualism in rats (Rattus Norvegicus), a simple form of cooperation in which two subjects work on operant task, receiving immediate and simultaneous sucrose reward for a joint action. To receive the sucrose reward, familiar pairs of rats were required to nose poke simultaneously. Following 44 training days, we examined the relation of social contact and ultrasonic vocalizations to the rat's cooperative behavior by testing the effects of inserting opaque, wire-mesh, or no partition--between subjects. Cooperative behavior (simultaneous nose-poking): (a) increased gradually during initial training; (b) decreased with the opaque partition (restricting visual, acoustic, and physical communication); (c) increased with a wire mesh partition restricting only physical contact); and (d) increased with the number of 50 kHz USV "happy" calls and the intensity of social interaction. The possibility of studying the development of cooperative behavior in laboratory rats using a simple procedure based on commercially available equipment may prove useful in modeling determinants of social behavior.     

Does Personality Smell? Accuracy of Personality Assessments Based on Body Odour

People are able to assess some personality traits of others based on videotaped behaviour, short interaction or a photograph. In our study, we investigated the relationship between body odour and the Big Five personality dimensions and dominance. Sixty odour samples were assessed by 20 raters each. The main finding of the presented study is that for a few personality traits, the correlation between self‐assessed personality of odour donors and judgments based on their body odour was above chance level. The correlations were strongest for extraversion (.36), neuroticism (.34) and dominance (.29). Further analyses showed that self–other agreement in assessments of neuroticism slightly differed between sexes and that the ratings of dominance were particularly accurate for assessments of the opposite sex. Copyright © 2011 John Wiley & Sons, Ltd.     

Prototypes are attractive because they are easy on the mind

People tend to prefer highly prototypical stimuli--a phenomenon referred to as the beauty-in-averageness effect. A common explanation of this effect proposes that prototypicality signals mate value. Here we present three experiments testing whether prototypicality preference results from more general mechanisms-fluent processing of prototypes and preference for fluently processed stimuli. In two experiments, participants categorized and rated the attractiveness of random-dot patterns (Experiment 1) or common geometric patterns (Experiment 2) that varied in levels of prototypicality. In both experiments, prototypicality was a predictor of both fluency (categorization speed) and attractiveness. Critically, fluency mediated the effect of prototypicality on attractiveness, although some effect of prototypicality remained when fluency was controlled. The findings were the same whether or not participants explicitly considered the pattern's categorical membership, and whether or not categorization fluency was salient when they rated attractiveness. Experiment 3, using the psychophysiological technique of facial electromyography, confirmed that viewing abstract prototypes elicits quick positive affective reactions.     

Effect of loudness on reaction time and response force in different motor tasks

Van der Molen and Keuss, in 1979 and 1981, showed that paradoxically long reaction times occur with extremely strong auditory stimuli when the task is difficult, e.g., choice-by-location or Simon paradigm. It was argued that this paradoxical behavior of RT is due to active inhibition of an arousal-dependent bypassing mechanism to prevent false responses. As the peak force, i.e., maximal force exerted by participants on a response key, is considered to be related to immediate arousal, we predicted that for extremely loud stimuli and for difficult tasks, lengthening of RT should be associated with reduction of peak force. Moreover, these effects should be enhanced when emphasis is on accuracy rather than speed. Although the relation between RT and intensity depended on task difficulty, no increase in RT was found for the loudest tones. Moreover, peak force increased monotonically with loudness, showing no tendency to be suppressed for loudest tones and difficult tasks.     

Mechanisms underlying spatial coding in a multiple-item Simon task

Choice responses are faster when target position and response side correspond than when they do not, even if target position is response-irrelevant. This "Simon effect" has also been observed in case of multi-item arrays. Generally, it is assumed that an automatically generated spatial response code is responsible for the effect. The referential-coding account assumes that this code is directly related to the target, although the moment of production of the code is not fully clear. The attention-shift account assumes that the code is directly related to the direction of the most recent attentional shift. An experiment was performed in which left or right target locations were indicated by arrows occurring before (precue), simultaneous with (simcue), or after (postcue) six-element arrays. Overt responses and EEG potentials were recorded. The Simon effect was present in all conditions, and decreased when responses were slower. No relation was found between amplitude of posterior lateralized components and the magnitude of the Simon effect. A posterior contralateral negativity was also found after presenting the arrays in the precue condition, which might reflect the reorienting of attention toward the target position. The results are more favorable to the referential-coding account although this account becomes very similar to the attention-shift hypothesis as the moment of formation of the spatial response code is related to effective target onset rather than to stimulus onset.     

Temporal-order judgment and reaction time for short and long stimuli

Summary The effect of intensity on visual latency was investigated. Visual latency was measured by two methods: simple motor reaction time (RT) and temporalorder judgment (TOJ). It was found, in accordance with previous studies, that the changes in RT were larger than TOJ latency when measured in the same range of intensity. Moreover, the relationship between TOJ latency and intensity was compared in two conditions: under so-called with-offset, the information about offset order was available for the subject, while under without-offset conditions it was not. It was hypothesized on the ground of Jakowski's 1991 study that the TOJ latency-intensity relation should differ for these two conditions because of the effect of intensity on visual persistence. We were unable to find any such effect.     

Chronic depressive syndrome--characteristics and therapeutic possibilities

The files of 322 patients with depressive syndromes in the period 1978-1987, covering 413 in-patient treatments, revealed therapeutic factors whose tendency is to lengthen the period of hospitalisation. There is no indication of therapeutic factors with a tendency to reduce the length of time spent in hospital. Lithium treatment was again shown to increase the hospital stay (chronicity of the overall disorder), others being (treatment with/Netofenazat), electric shock treatment during the initial disorder, and optimum simultaneous treatment with thymoleptics.     

Greater Male Variability in Creativity Outside the WEIRD World

Recent studies in creativity literature have demonstrated higher variability of creative ability between males and females, despite the lack of systematic sex differences in average scores on creativity tests. However, little is known about the causes of this variability and its generalizability beyond industrialized societies. This study presents the first evidence of the greater male variability in a sample of nonindustrialized, traditional Meru people residing in Kenya, Africa. The effect size of this difference was even greater than that reported in the majority of studies conducted on industrialized populations. Implications of these findings are discussed.