Using computer conferencing to formulate a computer simulation of transitive behavior

The activities of a group engaged in simulation modeling via computer conferencing are described, and the model which resulted from those activities is briefly outlined. The phenomena which were modeled were initially described in a series of studies by Trabasso and his colleagues. These studies centered upon exhibition of transitive choices by children and adults, and supported the hypothesis that the choices were guided by formation of “linear arrays“ of the choice objects.     

Evaluation of a continuing computer conference on simulation

A 20-day computer conference was held in preparation for a face-to-face meeting to produce a computer simulation. The conferencing resulted in the generation of seven different models and was excellent preparation for the subsequent meeting. Computer conferencing appears to hold great value for faculty development in a period of reduced faculty mobility.     

Development of an on-line problem-oriented system for the evaluation of mental health treatment services

Current on-line assessment applications are limited to mimicking instruments designed for paper and pencil. The development of an instrument designed specifically for on-line technology is described. The instrument provides research data on treatment effectiveness, clinical information for treatment planning, and management information for resource allocation.     

Vowel recognition: Inferences from studies of forward and backward masking

The recognition of brief vowels was studied in forward and backward masking tasks. In a series of experiments in which both target and mask parameters were systematically varied, two populations of subjects were identified. The majority (Nonmaskers) evidenced little masking at any interstimulus interval, while relatively fewer subjects (Maskers) evidenced backward masking (but not forward masking) over a 100-200 ms interval. Increasing target set size systematically increased masking for the Maskers but not for the Nonmaskers. Adding white noise to the targets increased the extent of masking for both groups. These results suggest (1) that masking does not impose a substantive constraint on vowel perception in running speech, and (2) that multiple strategies may exist for vowel recognition.     

Book reviews

Wyer, Robert S., Jr. Cognitive Organization and Change : an Information Processing Approach. Potomac, Maryland: Lawrence Erlbaum Associates. 1974. Pp. 502. £10.50.

Egan, J. P. Signal Detection Theory and ROC Analysis. New York: Academic Press. 1975. Pp. 277. £9.75. ISBN

Aldis, O. Play-Fighting. New York: Academic Press. 1975. Pp. 319. £8.75.

Warburton, D. M. Brain Behaviour and Drugs. London: John Wiley. 1975. Pp. 280. £6.95. ISBN 0471 91991 8.

Grieve, D. W., Miller, D., Mitchelson, D., Paul, J. and Smith, A. J. Techniques for the Analysis of Human Movement. London: Lepus Books. 1975. Pp. 177. £5.50.     

Comparison of child and adult vibrotactile thresholds as a function of frequency and duration

Psychophysical thresholds for the detection of sinusoidal vibration of the thenar eminence of the hand were determined for children and adults. The subjects in the child group were between 8 and 11 years old, and the adults were between 20 and 39 years old. Measurements were made for vibration frequencies ranging from 18 to 700 Hz and stimulus durations ranging from 28 to 1,000 msec. For both children and adults, thresholds were a Il-shaped function of stimulus frequency. However, the exact form of the function was influenced by the age of the subjects. At frequencies above 200 Hz, thresholds were virtually identical for children and adults, but below this frequency children were more sensitive than adults. This finding, in combination with known changes in the anatomy of the Pacinian corpuscle with age, is in agreement with a filter model of this cutaneous receptor. Furthermore, variation of stimulus duration resulted in data in agreement with the theory that two classes of mechanoreceptors, Pacinian and non-Pacinian, mediate the perception of vibration.     

Discrimination of time intervals marked by brief acoustic pulses of various intensities and spectra

Experienced observers were asked to identify, in a four-level 2AFC situation, the longer of two unfilled time intervals, each of which was marked by a pair of 20-msec acoustic pulses. When all the markers were identical, high-level (186-dB SPL) bursts of coherently gated sinusoids or bursts of band-limited Gaussian noise, a change in the spectrum of the markers generally did not affect performance. On the other hand, for 1-kHz tone-burst markers, intensity decreases below 25 dB SL were accompanied by sizable deterioration of the discrimination performance, especially at short (25-msec) base intervals. Similarly large changes in performance were observed also when the two tonal markers of each interval were made very dissimilar from each other, either in frequency (frequency difference larger than 1 octave) or in intensity (level of the first marker at least 45 dB below the level of the second marker). Time-difference thresholds in these two latter cases were found to be nonmonotonically related to the base interval, the minima occurring between 40- and 80-msec onset separations.