A different form of agraphia: Syntactic writing errors in patients with motor speech and movement disorders

Three patients are described who displayed syntactic writing errors in combination with a motor speech disturbance and impaired motor limb function. Two of the patients had bulbar amyotrophic lateral sclerosis (ALS). Agraphia appeared when verbal communication was no longer possible. Autopsy in one patient disclosed only lesions consistent with ALS. The third patient had palilalia and chorea and, although not aphasic, his written language showed persistent syntactic errors. We hypothesize that the agraphia in these patients occurred because of the combination of disordered feedback from the motor speech apparatus and limbs.     

Time errors are perceptual

Summary Methods for the measurement of time-errors (TEs) in the comparison of successive stimulus magnitudes are discussed. Combining a Thurstonian scaling method with the assumption of a fixed subjective width of the equal category, independent of stimulus level, a ratio scale for subjective differences within pairs of successive stimuli is derived. In a tone duration comparison experiment, with the TE defined in the terms of these subjective duration differences, data from four experimental groups were compared, the groups using different modes of judging and responding. Only minor effects of this factor were found, and hence it is concluded that the TE is a true perceptual phenomenon rather than an effect of response bias, criterion bias, or mediating verbal responses to the absolute level of stimulation. The quantitative results are interpreted in terms of a general model for the comparison of successive stimuli, employing the concepts of adaptation and differential weighting of sensation magnitudes.This investigation was supported by grants to the author from the University of Stockholm and from the Swedish Office of Administrative Rationalization and Economy (for computer time), and by grants to Mats Björkman and Hannes Eisler from the Swedish Council for Social Science Research, whose free consultation service at the Department of Statistics, University of Stockholm, also benefited the author.     

Crowding: Effects of Group Size,Room Size,or Density?

The separate effects of group size, room size, and density (space per person) were investigated for subjects responding interactively or coactively to perceptual and cognitive tasks. The major findings are that crowding has greater effects on "feelings" and "interpersonal perceptions" than on task performance. Where crowding did have effects, they appeared to be mediated more by group size and, to some degree, room size than by density, especially for males. Female subjects appeared somewhat more density oriented than male subjects.     

Periodicity pitch perception and its upper frequency limit in cats

We have established a procedure for behavioral assessment of periodicity pitch perception in the cat. This procedure requires the training of cats to make a differential response to two different pure tones, and then testing for the transfer of learning when complex stimuli known to produce periodicity pitch sensations in humans are substituted for the pure tones. Complex stimuli consisted of three to five harmonically related frequencies of the same amplitude and phase. Eight cats were the subjects of these experiments. Two of them were controls. It is demonstrated here that cats do perceive periodicity pitch. We also used this procedure to measure the upper frequency limit of periodicity pitch perception for two cats. The frequencies tested were 100, 200, 300, 400, 600, 800, 900, and 1,200 Hz. The data indicate that the upper frequency limit of periodicity pitch perception in the cat is on the order of 600 to 800 Hz. There is a trend of decreasing prominence of the perception of periodicity pitch as the component frequencies are increased. These results are parallel to the human psychophysical data.     

A developmental study of timing behavior in 4 1/2- and 7-year-old children

The present study investigated effects of age and instructions on temporal regulations of behavior in children. In the first experiment 4 1/2-year-old and 7-year-old subjects were trained with a DRL (differential reinforcement of low rates) 5-s and a DRL 10-s schedule. Results demonstrate that age and timing performance are related. Seven-year-olds are more efficient than the 4 1/2-year-olds. A striking decline in the 4 1/2-year-old children's capacity to space responses was observed in the DRL 10-s schedule as compared to the DRL 5-s schedule. Analysis of individual performances suggests that the evolution of DRL performance between 4 and 7 years of age depends not only on the development of the capacity to delay responding but also on the acquisition of the ability to represent the reinforcement contingencies, that is, the temporal parameters of the task to oneself. In order to test this hypothesis a second experiment was conducted where instructions to wait between operant responses were given to a group of 4 1/2-year-old subjects at the beginning of a DRL 5-s and a DRL 10-s schedule. The results show that these instructions enhance DRL performance. By directing the 4 1/2-year-old subjects' attention to the temporal requirements of the task, instructions led to efficient performance and accurate timing of responses to the DRL schedule.