Duration discrimination is better with food access as the signal than with light as the signal

In Experiment 1 a go/no-go discrimination procedure was used to compare control of five pigeons' keypecking by food-access duration with control by light duration. Pecks to an illuminated key were reinforced with grain following 10-sec presentations of food access or houselight, but not after 5-sec presentations of either stimulus. Each subject discriminated food-access duration faster and to a greater degree than light duration. In four between-subject replications, pigeons discriminated food-access duration better than the duration of a localized light, the feeder light and a keylight, and with either water or food as reinforcement. In Experiment 2 control by durations of food access and light was compared using a conditional right-left choice procedure (two pigeons), and a delayed symbolic matching-to-sample procedure (six pigeons). Under both, choice accuracy again was higher on food-access trials. The results of Experiment 3, in which two pigeons received generalization trials with durations of food access and light that were intermediate to the training values, confirmed that responding was controlled by the duration dimension of both food access and light. The superior control by food access is consistent with previous evidence that food is an effective and memorable stimulus, possibly because of its biological importance. These results also provided empirical support for the commonly made assumption that stimuli differ in effectiveness. As well, the results show that the stimulus to be discriminated can play an important role in the accuracy of duration disciminations, a fact which has implications for the study of temporal discriminations in animals.     

Developmental dyslexia: Electrophysiological evidence of clinical subgroups

Event-related potentials (ERPs) to word and to musical-chord stimuli were recorded in 13 dyslexic boys and 13 age-matched normal readers. Normal readers and dyslexics whose reading handicaps involved visual-spatial processing deficits had greater word versus musical-chord ERP waveform differences over the left as compared to the right hemisphere. Dyslexics whose reading difficulties were related to auditory-verbal processing deficits did not exhibit this asymmetry. These results are interpreted as supportive of the hypothesis that the latter group of dyslexics has failed to develop normal left hemisphere specialization for processing of auditory-linguistic material.     

Myths of brief family therapy task intervention

The steps of brief treatment promoted by Watzlawick, Weakland and Fisch (1974) and Haley (1976, 1987) elude the novice family practitioner, especially in deriving end-of-the session task interventions from earlier assessment. The gap between the suggested procedure and the beginning clinician's results is just starting to surface in brief therapy research. This paper compares the above authors' interactional and problem-solving approaches, contextualizing their theories in light of training issues emerging from preliminary research. The ensuing myths of brief family therapy task intervention typically espoused by the neophyte are thus demystified, making what experience teaches more accessible.     

A method for automatically recording topographical differences in pigeons’ keypecking for food and water reinforcers

The topography of pigeons’ keypecking responses for food reinforcers is visibly different from the keypeck topography for water reinforcers. Previous methods of recording topographies have been complex and not without problems. A simple inexpensive modification of a standard pecking key permits the recording of two components of the topography in sufficient detail to allow the detection of these topographical differences.     

The contribution of vowel duration,F0 contour,and frication duration as cues to the/juz/-/jus/distinction

A model was quantified to describe the integration of vowel duration, fricative duration, and fundamental frequency (F₀) contour as cues to final position fricatives differing in voicing. The basic assumptions are that perceived vowel duration and perceived frication duration are cues to the identity of final position fricatives and that both F₀ contour and vowel duration influence perceived vowel duration. Binary choice and rating responses to synthetic stimuli varying independently along the three dimensions were collected. The results were consistent with the assumption that F₀ contour operates by modifying perceived vowel duration, which is a direct cue. Unfortunately, the nature of the modification appears to be very similar in form to that which results from the integration of two independent cues in syllable identification. Therefore, the results do not allow a rejection of the idea that the perception of F₀ contour may directly cue the identity of final position fricatives.     

Direct and vicarious censure in the control of interracial aggression1

An experiment explored the relative effectiveness of two strategies for controlling interracial aggression: observing other individuals censured for aggression and potential direct censure of the aggressor himself. Subjects were provided with an opportunity to aggress under conditions designed to maximize or reduce each type of censure. A principal components analysis of the data revealed two orthogonal variates: direct aggression and indirect aggression. It was found that both observed censure and potential direct censure were effective in modifying directly aggressive responses. However, these forms of censure interacted in their effect on indirect aggression, such that observed censure was effective in reducing indirect aggression only under conditions of potential direct censure.     

Sentence repetition in preschoolers: Effects of length,complexity, and word familiarity

Seventy-two sentences presented to ten preschool children for repetition were designed so that three sentence construction factors varied independently. The factors were (1) length in number of words, (2) complexity of personal pronouns and main verbs as scaled by Lee (1974), and (3) word familiarity, defined as common vocabulary or the substitution of a nonsense word in place of a typical noun or verb in the model sentence. Three methods were employed for scoring the children's responses: (1) number of retained words, (2) Developmental Sentence Scoring (Lee, 1974), and (3) Stephens's Categories (Stephens, 1974). Eighteen sentences were re-presented for the assessment of reliability. The results of multiple regression analyses indicated that length was the important contributing factor in the children's responses to the model sentences and that Stephens's Category Scale of response scoring was the most sensitive method for detecting the influence of the three sentence factors on the children's responses.     

Perception of pictorial depth cues by pigeons

Pigeons were trained to discriminate pictures of intact objects from pictures of objects in which both depth from shading and depth from perspective cues were manipulated. Depth from shading was manipulated either by scrambling or by removing three-dimensional shading cues. Depth from perspective was manipulated either by presenting pictures of objects with a two-dimensional outline (i.e., a square) or with a three-dimensional outline (i.e., a cube). Transfer tests with novel images suggest that pigeons perceive and utilize both types of pictorial depth cues. The implications of these results for our understanding of picture perception in pigeons are discussed.