The ontogeny of intentional communication in chimpanzees in the wild

The onset of intentional communication in children's first year of life represents a major milestone in human cognitive development. Similarly, it is well established that our closest living relatives, the great apes, communicate with signals characterized by at least first‐order intentionality. Despite the well‐documented influence of developmental experiences on socio‐cognitive abilities in apes, the developmental trajectory of intentional signal use as well as effects of social exposure remain poorly understood under naturalistic conditions. Here, we addressed these issues by studying the ontogeny of intentional communication in chimpanzee infants of two subspecies (Pan troglodytes schweinfurthii/verus) and communities living in their natural environments. Overall, we found that gestures and bimodal signal combinations were most commonly accompanied by markers of intentional communication: audience checking, persistence to the goal, and sensitivity to recipient’s attentional state. Within individuals, the proportion of communicative behaviours associated with goal persistence and sensitivity to attention increased with age. Cross‐sectional comparisons between infants revealed an age effect on the use of audience checking. Context, interaction partner and site affiliation affected the production of specific markers irrespective of infants' age. The present study provided hitherto undocumented evidence for the development of three important markers of intentional communication in great apes. Moreover, our results suggest that social exposure impacts early intentional signal use.     

Identity affirmation and social movement support

It is argued that the power of collective identification to mobilize people for collective action such as social movement support derives at least partly from processes of identity affirmation. The hypothesized identity‐affirming function of social movement support is tested in two laboratory experiments which revolve around collective identity as a supporter of the peace movement. In Experiment 1, we predicted and found that people who strongly identified with the peace movement showed more movement support (i.e. made more monetary donations to the peace movement) under conditions of uncertain as opposed to certain possession of identity as a movement supporter. In Experiment 2, we replicated this finding, but also found, in accordance with the notion of substitution, that the mobilizing effect of uncertain collective‐identity possession was undermined when an identity symbol was available that could function as a surrogate for more costly identity‐affirming behaviour. Further conceptual and social implications of the identity‐affirming function of social movement support are discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Complete recovery of olfactory associative learning by activation of 5-HT4 receptors after dentate granule cell damage in rats

Bilateral intradentate injections of 3.0 μg of colchicine induced a substantial loss of granule cells and damage to the overlying pyramidal cell layer in region CA1 in adult male Long-Evans rats. All rats with such lesions showed a significant associative learning deficit in an olfactory discrimination task, while being unimpaired in the procedural component of this task. Injection of a partial selective 5-HT₄ agonist (SL65.0155; 0.01 mg/kg, i.p., vs. saline) before the third of six training sessions enabled complete recovery of associative learning performance in the lesioned rats. Activation of 5-HT₄ receptors by a selective agonist such as SL65.0155 might therefore provide an opportunity to reduce learning and memory deficits associated with temporal lobe damage, and could be useful for the symptomatic treatment of memory dysfunctions related to pathological aging such as Alzheimer’s disease.     

Working memory performance after acute exposure to the cold pressor stress in healthy volunteers

Effects of acute stress exposure on learning and memory have been frequently studied in both animals and humans. However, only a few studies have focused specifically on working memory performance and the available data are equivocal. The present study examined working memory performance during the Sternberg item recognition task after exposure to a predominantly adrenergic stressor. Twenty four healthy subjects were randomly assigned to a stress group or a control group. The stress group was exposed to the cold pressor stress test (CPS; i.e. insertion of the dominant hand into ice water for 60s), while 37 °C warm water was used with the control group. Twenty minutes after the stress exposure, working memory performance was tested with the Sternberg item recognition task with three levels of cognitive load. Sympathetic nervous system and hypothalamic pituitary adrenocortical (HPA) axis activation during CPS, were assessed by measuring heart rate and salivary cortisol before and during (heart rate) or 30 min after (cortisol) the stress procedure. Exposure to the CPS test was associated with a significant increase in heart rate but no increase in salivary cortisol. Participants exposed to the stress procedure showed significantly shorter reaction times during trials with higher cognitive load but tended to show higher false alarm rates than control subjects. The present results indicate that exposure to CPS can be associated with signs of both enhanced and impaired working memory performance. The observed behavioral pattern might represent a form of streamlined information processing advantageous in a threatening situation.     

When remembering causes forgetting: retrieval-induced forgetting as recovery failure

Retrieval practice on a subset of previously learned material can cause forgetting of the unpracticed material and make it inaccessible to consciousness. Such inaccessibility may arise because the material is no longer sampled from the set of to-be-recalled items, or, though sampled, its representation is not complete enough to be recovered into consciousness. In 2 experiments, it was examined whether retrieval-induced forgetting reflects a sampling or recovery failure by studying the time course of cued recall in this type of situation. Although retrieval practice reduced recall totals of the unpracticed items, in both experiments, the forgetting was not accompanied by an effect on the items' response latencies. This pattern of results is consistent with the view that inhibited items are successfully sampled but, because of a reduction in their activation level, do not exceed the recovery threshold.     

The impact of emotional stress early in life on adult voluntary ethanol intake-results of maternal separation in rats

The combination of genetic and environmental factors determines the individual vulnerability for excessive ethanol intake, possibly leading to dependence. The environmental influences early in life represent examples of determinant factors for adult behaviour and can be protective as well as risk factors. Maternal separation is one model to examine the long-term consequences of early environmental experiences on neurochemistry and behaviour, including drug-taking behaviour in experimental animals. In the present review, findings from studies using repeated short and prolonged periods of maternal separation, with emphasis on effects on voluntary ethanol intake in rats with or without a genetic predisposition for high voluntary ethanol intake, are summarized. Despite some contradictory results, the general picture emerging shows that short periods of maternal separation during the postnatal period result in a lower adult voluntary ethanol intake in male rats. Prolonged periods of maternal separation were found to induce a high voluntary ethanol intake in male rats, including rats with a genetic predisposition for high ethanol intake. Results from the literature also show that changes were not just related to time of separation but were also related to the degree of handling. Interestingly, in terms of voluntary ethanol intake, female rats were generally not affected by postnatal maternal separation. The reasons for these sex differences need further investigation. In terms of neurobiological consequences of maternal separation, conclusive data are sparse and one of the future challenges will, therefore, be to identify and characterize underlying neurobiological mechanisms, especially in the individual animal.     

Personal problem-solving scoring of the TAT: sensitivity to training

The Thematic Apperception Test (TAT; Murray, 1943) is one of the most frequently taught and administered projective instruments in the United States. Nevertheless, formal scoring systems are not often used when evaluating story responses; thus, the reliability and validity of response interpretations remain controversial. The sensitivity-to-training of a procedure that uses the TAT to assess personal problem-solving skills, namely the Personal Problem-Solving System (PPSS; Ronan, 1990), was evaluated. In Experiment 1, undergraduate students received either detailed (n = 30) or minimal (n = 29) training in the problem-solving skill of generating alternative solutions to personal problems and subsequently wrote responses to three TAT cards. In Experiment 2, subjects received either detailed (n = 22) or minimal (n = 22) training in a utility model of decision making and thereafter responded to the same three TAT cards. Subjects who received detailed training, when compared to their minimally trained counterparts, reported an increase in their knowledge of the relevant problem-solving skill, and this increased knowledge influenced their responses to the TAT cards as measured by the PPSS scores. Implications for the construct validity of the PPSS are discussed.