Which cues are available to 24-month-olds? Evidence from point-of-gaze measures during search

In previous research 2-year-olds have failed to show knowledge of solidity in a search task in which a ball rolled behind a screen and was stopped by a barrier. The screen had four doors and the barrier was visible above the door hiding the ball. To establish what cues 2-year-olds might be using, precise point-of-gaze measures were taken during the hiding event. A transparent screen with opaque doors provided two cues: (1) the ball could be tracked until it failed to emerge, and (2) the barrier's position could indicate the correct door. Point-of-gaze measures revealed that children failed to use the more indirect cue of the barrier, which requires reasoning and spatial integration. Their search success was predicted only by the more immediate cue of actively tracking the ball. These findings support the claim that children use best those cues directly related to the object's disappearance, while failing to use cues that entail higher cognitive demands.     

Book reviews

With Faith and Fury. Delos McKown. New York: Promethius Books, 1985. pp 440. $16.95

The Sacred in a Secular Age. Phillip E. Hammond, Editor. University of California Press, 379 pages (p/b) $8.95 (£8.50)     

Concept identification: Effect of the intertrial interval on the efficacy and consistency of information processing

Two experiments following identical procedure except for the feedback duration (respectively, 2 sec and 1.5 sec) and the intertrial interval (respectively, 1 sec and 3 sec) are compared with respect to three sequential statistics whose theoretical interpretation is related to the degree of optimality of information processing. The results indicate that the values of the theoretical parameters representing the efficiency of information processing, the consistency of trial-by-trial decisions, and the efficacy of reinforcement are greater in the 3-sec interval condition. This is interpreted as a tentative explanation of the well-known effect of intertrial interval on the difficulty of the task with respect to the mean number of trials to criterion.     

Dominance assertion in male chimpanzees (Pan troglodytes)

The social relations of three adult males in a captive chimpanzee group were evaluated for 12 months. The observations encompassed a period of transition in the dominance hierarchy providing an opportunity to assess behavioral patterns involved in the initiation of status changes. This study shows that dominance in the chimpanzee is expressed primarily through ritualized and non-contact behavior rather than by overt aggression. In particular, display behavior is important for indicating dominance rank, in communicating aggressive intent, and as a prelude to status struggles. The functional relationships between status, displays and other socio-sexual behavior patterns are presented.     

The effects of emotional content on reality-monitoring performance in young and older adults

Reality monitoring refers to a person's ability to distinguish between perceived and imagined events. Prior research has demonstrated that young adults show a reality-monitoring advantage for negative arousing information as compared with neutral information. The present research examined whether this reality-monitoring benefit extends to positive information in young adults and whether older adults show a reality-monitoring advantage for emotional information of either valence. Two studies revealed no evidence for a reality-monitoring advantage for positive information; in both age groups, the reality-monitoring advantage existed only for negative information. Older adults were, however, more likely to remember that a positive item had been included on a study list than they were to remember that a nonemotional item had been studied. Young adults did not show this mnemonic enhancement for positive information. These results indicate that although older adults may show some mnemonic benefits for positive information (i.e., an enhanced ability to remember that a positive item was studied), they do not always show enhanced memory for source-specifying details of a positive item's presentation.     

A bribe, “living-bread,” and a white tablecloth

This article describes marital therapy with a Holocaust survival couple in which the wife's demands for living bread plays a highly symbolic role in the marital dynamics. The author draws interesting parallels between the experience of the couple and the meaning of the therapy experience for herself.     

Adaptive spatial working memory assessments for aging pet dogs

Assessments for spatial working memory (SWM) in pet dogs that can detect age-related cognitive deficits in a single session may aid in diagnosing canine dementia and may facilitate translational research on Alzheimer’s disease in humans. Adaptive testing procedures are widely used in single-session assessments for humans with diverse cognitive abilities. In this study, we designed and deployed two up-down staircase assessments for SWM in which 26 pet dogs were required to recall the location of a treat hidden behind one of two identical boxes following delays of variable length. In the first experiment, performance tended to decline with age but few dogs completed the test (n?=?10). However, all of the dogs that participated in the second experiment (n?=?24) completed the assessment and provided reliable evidence of learning and retaining the task. Delay length and age significantly predicted performance supporting the validity of this assessment. The relationships between age and performance were described by inverted U-shaped functions as both old and young dogs displayed deficits in weighted cumulative-scores and trial-by-trial performance. Thus, SWM in pet dogs may develop until midlife and decline thereafter. Exploratory analyses of non-mnemonic fixation strategies, sustained engagement, inhibitory control, and potential improvements for future SWM assessments which adopt this paradigm are also discussed.