Adaptation in stereoscopic depth constancy

Stereovision is a complex process because perceived depth intervals depend not only on retinal disparity, but also on cues for distance. Because disparity decreases in proportion to the square of the object distance, a compensation process called constancy of stereoscopic depth makes the necessary correction in the perception of depth by taking object distance into account. This compensation process was altered by adaptation. Subjects were exposed to artificial conditions where disparity decreased in proportion to distance instead of distance squared. Alterations in depth perception amounting to 20% were obtained.     

Evidence in support of word unitization

In each of five experiments, the subjects viewed tachistoscopically presented pairs of letters and made speeded comparison judgments on the basis of name identity. On most trials, a noise letter string (word or anagram) was placed directly between the target letters. The results indicated that correct “same” RTs were a function of noise item type and its relation to target letters. Anagrams increased RTs more than their counterpart words, except when the noise word was either unmeaningflul or response incompatible with respect to the target letters (e.g., B Tea b). The interference effects were also found to be independent of sequence length. It was posited that the subjects were unable to completely ignore the irrelevant attributes of the displays and that under certain conditions, the subjects were able to identify the noise items in a holistic fashion. The data were interpreted in terms of a unitization hypothesis of word recognition, response competition, and a continuous-flow conception of information processing.     

Overselective response to social stimuli by autistic children

Previous studies have shown that when presented with a complex stimulus input, autistic children typically respond to only one of the elements of the complex. This phenomenon was called stimulus overselectivity (or overselective attention). The present investigation sought to determine if this overselectivity might be a possible basis for the deviant social behavior in autistic children. Autistic and normal children were trained to discriminate between clothed girl and boy doll figures. After the children had acquired this discrimination, the individual clothing components and the heads were systematically interchanged between the figures. Thus, it could be determined which component(s) the children had used to make the discrimination. The autistic children demonstrated stimulus overselectivity in that they formed the discrimination between the boy and girl figures on the basis of only one component or of peculiar combinations of components. For example, one child discriminated the figures on the basis of shoes. In contrast, the normal children responded primarily to the figures' heads but could also respond correctly to other parts. These findings are consistent with previous research on stimulus overselectivity and have implications for understanding the difficulty autistic children show in forming meaningful social relationships.This investigation was supported by U.S. Public Health Service Research Grant 11440 from the National Institute of Mental Health.The authors express their appreciation to James Q. Simmons, Associate Chief, Mental Retardation and Child Mental Health Programs, Neuropsychiatric Institute, University of California, Los Angeles; and Norbert Rieger, Superintendent of Children's Services, Camarillo State Hospital, Camarillo, California. They are also grateful to Robert Koegel and to Thomas Willis for their valuable suggestions and to Meredith Gibbs for her assistance in data collection.     

The concreteness of attributes in concept learning strategies

Ss were presented with conjunctive concept learning tasks using geometric stimuh in two experiments and using combinations of abstract characteristics in two other experiments. Evidence indicated that the conjunctive hypotheses for geometric stimuli were not mediated by component values but were sampled as unitized wholes. In contrast, conjunctive hypotheses for abstract attributes were sampled via independent combinations of component values. The differential processing was not found to be associated with the variation of stimuli on the verbal-nonverbal dimension.