AN EXPERIENTIALLY DERIVED BASE-RATE ERROR IN HUMANS

Abstract— Two experiments tested college students in a delayed matching-to-sample procedure designed to explore how multiple competitive sources of control interact in determining choice behavior. The primary sources of potential control were the frequency with which each of two colors was correct (base rates) and the accuracy of a sample in predicting the correct choice (accuracy rate). In one experiment, subjects ignored the base rates, and therefore made nonoptimal choices. These results mimicked the well-known base-rate error found in verbal responses to questions. In a second experiment, manipulations to increase subjects' motivation did not alleviate the error significantly. Together, these results suggest that the base-rate error may represent a broad behavioral pattern not restricted to verbal arenas. The results are compared with previous attempts to reconcile behavioral and cognitive lines of experimentation.     

Spatial compatibility of signal-response position in pointing

Two experiments are reported in which, by means of a pointing task, we studied the stimulus-position effect, i.e. the inverted U-shape form of the reaction-time function in relation to stimulus position in tasks in which stimuli and/or responses are arranged in a horizontal array. The response consisted of aiming the index finger from a central starting point at a target area on a screen. Reaction time was the main dependent variable. The spatial relation between the position of the imperative signal and the position of the response was manipulated by varying the spatial S-R compatibility and physical distance that separated the positions of stimulus and response. The stimulus-position effect was shown to depend on the compatibility of the S-R relation (Exp. 1). In Exp. 2 it was found that the modulation of the stimulus-position effect by spatial compatibility disappeared completely when the distance between the positions of stimulus and response was reduced. None of the experiments revealed that the stimulus position effect depended on signal discriminability, which renders an interpretation of this effect in terms of perceptual processes unlikely. We argue that the attentional model of spatial coding provides the most reasonable explanation of the obtained reaction-time patterns.     

A twin study of personality and temperament during middle childhood

In a study of 105 same-sex twin pairs, ages 7 to 10 years, maternal ratings on 23 bipolar scales yielded six factors designated as compliant morality, applied cognitive, sociability, emotionality, tough-mindedness, and activity-distractibility. Analyses by twin pairs (68 identical, 37 fraternal) indicated that correlations for identical pairs were significantly higher than fraternal pairs on all but one factor: tough-mindedness. Profile analyses for the six factors indicated that the profiles of scores across the factors were more concordant for the identical twin pairs. Correlations obtained from the individual scales produced differences between the identical and fraternal twin pairs as well. Overall, the data suggested that several components and the total organization of those components of personality and temperament are genetically influenced.     

Group identity and peer relations: A longitudinal study of group identity,perceived peer acceptance,and friendships amongst ethnic minority English children

This research examined whether peer relationships amongst ethnic minority status children reflect the social groups to which children belong and the degree to which they identify with these groups. A longitudinal study was conducted to investigate the influence of group identities (i.e., ethnic and national) on children's perceived peer acceptance and preference for same‐ethnic friendships. Measures of ethnic and English identification, perceived peer acceptance, and friendship choice were administered to 207 south‐Asian English children, aged between 5 and 11, at two time points 6 months apart. In line with predictions, longitudinal analysis showed that bicultural identification (i.e., higher ethnic and English identity) was related to higher perceived peer acceptance and less preference for same‐ethnic friendships. Importantly, as hypothesized, this finding was limited to the older children with more advanced social‐cognitive abilities. The results suggest that older children who adopted a bicultural identity were able to strategically ‘flag’ their multiple group identities, within their multicultural peer groups, to obtain acceptance amongst the maximum number of peers and show less preference for same‐ethnic friendships. This study extends previous peer relations research, which has typically focused on individual social deficits or classroom norms, by showing that group identities influence peer relationships amongst ethnic minority status children.     

Acting intentionally and the side-effect effect

The concept of acting intentionally is an important nexus where theory of mind and moral judgment meet. Preschool children's judgments of intentional action show a valence-driven asymmetry. Children say that a foreseen but disavowed side effect is brought about "on purpose" when the side effect itself is morally bad, but not when it is morally good. This is the first demonstration in preschoolers that moral judgment influences judgments of whether something was done on purpose (as opposed to judgments of purpose influencing moral judgment). Judgments of intentionality are usually assumed to be purely factual. That these judgments are sometimes partly normative-even in preschoolers-challenges current understanding. Young children's judgments regarding foreseen side effects depend on whether the children process the idea that the character does not care about the side effect. As soon as preschoolers effectively process the theory-of-mind concept "not care that P," children show the side-effect effect.     

Saccadic latency as a function of target duration in a spatial localization task

This study examined a potential confound in the inverse relationship between target duration and saccadic latency reported by Adam, Ketelaars, Kingma, and Hoek in 1993. Eight participants located a briefly flashed target by moving the eyes and the cursor toward its position in a (backward) mask condition and in a no-mask condition. Analysis showed similar saccadic latencies in both conditions, thereby refuting the potentially confounding role of the backward masking procedure. It is tenatively suggested that the longer saccadic latencies noted for shorter target durations may be associated with delayed accumulation of evidence for the detection of the target.     

The origin of the interaction between learning method and delay in the testing effect: The roles of processing and conceptual retrieval organization

Recent research has demonstrated a relationship between retrieval organization and the efficacy of prior repeated retrieval on delayed tests. The present study asked why repeated study engenders higher recall at a short delay despite lower retrieval organization but produces a decline at a long delay, and why repeated retrieval engenders lower recall at a short delay despite higher retrieval organization but produces stable recall over time. This relationship was examined through the inclusion of two successive recall tests—one immediately after learning method and one a week later. Results replicated the interaction in recall between learning method and delay characterizing the testing effect and, critically, revealed the qualitative differences inherent in the retrieval organization of each method. Specifically, stable recall in repeated retrieval was accompanied by strong and sustained conceptual organization, whereas organization for repeated study was tenuous and weakened across tests. These differences quantitatively were assessed through the use of five targeted analyses: specifically, the examination of cumulative recall curves, the accumulation of organization across time (a curve akin to cumulative recall), item gains and losses across time, changes in the size of categories across time, and the fate of specific clusters of recalled items across time. These differences are discussed within the context of differential processes occurring during learning method.     

Bridging a yawning chasm: EEG investigations into the debate concerning the role of the human mirror neuron system in contagious yawning

Ongoing debate in the literature concerns whether there is a link between contagious yawning and the human mirror neuron system (hMNS). One way of examining this issue is with the use of the electroencephalogram (EEG) to measure changes in mu activation during the observation of yawns. Mu oscillations are seen in the alpha bandwidth of the EEG (8–12 Hz) over sensorimotor areas. Previous work has shown that mu suppression is a useful index of hMNS activation and is sensitive to individual differences in empathy. In two experiments, we presented participants with videos of either people yawning or control stimuli. We found greater mu suppression for yawns than for controls over right motor and premotor areas, particularly for those scoring higher on traits of empathy. In a third experiment, auditory recordings of yawns were compared against electronically scrambled versions of the same yawns. We observed greater mu suppression for yawns than for the controls over right lateral premotor areas. Again, these findings were driven by those scoring highly on empathy. The results from these experiments support the notion that the hMNS is involved in contagious yawning, emphasise the link between contagious yawning and empathy, and stress the importance of good control stimuli.