Children''s understanding of belief and disconfirming visual evidence

Data from 3- to 5-year-old children show that even the youngest have an understanding that a story character cannot think an object is in a box when the character looks into the empty box. This understanding is, however, limited to the case where children share the same visual perspective with the character. When visual perspectives are different the relevant knowledge develops shortly after 4 years at about the time that children master the false belief task. These results are interpreted as young children using an implicit constraint that “think” cannot be applied in view of disconfirming visual evidence. This implicit knowledge becomes explicit and, thus, perspective independent with some delay.     

Mental representation of length and weight series and transitive inferences in young children

Forty-eight second graders (8 years of age) were trained on length or weight relationships between adjacent members of a five-term series of colored objects. Feedback was visual and of either minimal or strong salience. Differences in weight were assessed by either a balance scale or a spring scale. Results showed that more salient visual feedback reduced the learning effort for length but not for weight comparisons. After training children were tested on all possible object pairs. Children's comparisons of items by length were very accurate in contrast to their comparisons by weight. An explanation for these findings is suggested by the data from a group of 6-year-olds who were trained on two independent pairs of a four-term series. Test results showed that subjects spontaneously encoded absolute lengths but tended to ignore information about the absolute weight of objects. It is suggested that high test accuracy depends on stimulus material for which the absolute values of the relevant dimension are encoded. The implications for taking test performance as an indicator of “transitive reasoning” ability are discussed.     

Differences in the dissipation of the effect of adaptation to two kinds of field displacement during head movements

When Ss were simultaneously adapted to horizontal and to vertical target displacements of equal rate during head turning about a vertical axis, the adaptation effects measured by one-trial tests immediately after the adaptation period were about equal. But retests after a time lapse of 10 and 20 min, during which S sat immobile and with eyes closed, showed a greatly different rate of dissipation of the two adaptation effects. After a lapse of 20 min, the effect of adaptation to horizontal target displacements had been reduced to 37%, whereas the effect of adaptation to vertical displacements at this final test still stood at 80% of the initial measurement. The decline over 20 min in the latter case was so smail that it could readily be ascribed to an effect of the two tests that preceded the final test. These two tests represented an effective exposure to natural viewing conditions and hence caused an unlearning of the adaptation, an effect whose existence we had demonstrated in previous work with the one-trial test.     

From the left to the right: How the brain compensates progressive loss of language function

In normal right-handed subjects language production usually is a function oft the left brain hemisphere. Patients with aphasia following brain damage to the left hemisphere have a considerable potential to compensate for the loss of this function. Sometimes, but not always, areas of the right hemisphere which are homologous to language areas of the left hemisphere in normal subjects are successfully employed for compensation but this integration process may need time to develop. We investigated right-handed patients with left hemisphere brain tumors as a model of continuously progressive brain damage to left hemisphere language areas using functional neuroimaging and transcranial magnetic stimulation (TMS) to identify factors which determine successful compensation of lost language function. Only patients with slowly progressing brain lesions recovered right-sided language function as detected by TMS. In patients with rapidly progressive lesions no right-sided language function was found and language performance was linearly correlated with the lateralization of language related brain activation to the left hemisphere. It can thus be concluded that time is the factor which determines successful integration of the right hemisphere into the language network for compensation of lost left hemisphere language function.     

Reaction time as a function of stimulus intensity for the monkey

Monkeys were trained to release a telegraph key in response to a visual or auditory stimulus. The latency of the key release response was measured for different stimulus intensities. In general, the relation between latency and intensity is inverse and exponential with greater variability of latency at the lower intensities. Some preliminary data involving differential reinforcement of short latencies are presented.