MULTIDIMENSIONAL SCALING OF LARGE CHROMATIC DIFFERENCES BY NORMAL AND COLOR-DEFICIENT SUBJECTS

The following two articles offer a glimpse at current experimental psychology in the Soviet Union, normally screened from the English-speaking world by all but impenetrable language barriers. The accompanying Commentary by Tarow Indow helps place these contributions in the framework of contemporary work on the psychophysics of color perception.   Abstract —
Fifteen normal trichromatic subjects, two protanopes, and two deuteranopes judged pairs of successively presented foveal color stimuli. Multidimensional scaling of the data yielded estimates of a three-dimensional space with axes interpreted as red–green, blue-yellow, and white-black. For color-deficient subjects, the average radius of the space differed from that of normals, being smaller for the protanopes and larger for the deuteranopes. For both types of color deficiency, the blue-yellow axis was stretched relative to the red-green, more strongly in the protanopes. The findings are taken to support the generality of a "spherical" model.     

ODAP: a stand-alone program for observational data acquisition

A software program written to collect real-time, observational data is described. The flexible program allows customized behavior codes and observational durations and simultaneously records both timed and counted events. The data are collected by means of single keystrokes, automatically stored to disk with 100th of a second resolution and summarized for each observational session. The program’s database files are dBASE III PLUS compatible and may be browsed, edited, or converted to ASCII files from the program’s main menu. Field testing demonstrated the efficiency and interobserver reliability of the program (for frequency,r=0.81; for durational behaviors,rs=0.89 and 0.96). The software operates on IBM XT/AT/PS 2s and most clones with PC/MS DOS version 2.0 or greater.     

Extending a class of motion stimuli to study multiattribute texture perception

We present a class of stimuli that makes it possible to study the interaction of visual attributes in forming textural patterns. These stimuli are obtained in a simple manner from a class of motion stimuli that we described earlier (Papathomas & Gorea, 1988). The main advantages of the texture stimuli presented in this paper are: (1) each attribute can be arranged simultaneously with, but independently of, other attributes, (2) an arbitrary number of attributes can be used, (3) the interaction of attributes can be studied systematically, (4) direct comparison of two attributes is possible with stimuli in which the two are arranged to form competing patterns, and (5) because of the similarity to the motion stimuli, the relationship between texture and motion mechanisms can be investigated.     

Performance of humans in concurrent avoidance/positive-reinforcement schedules

Performance maintained under concurrent schedules consisting of a variable-interval avoidance component and a variable-interval positive-reinforcement component was studied in three human subjects using points exchangeable for money as the reinforcer. The rate of responding in the avoidance component increased, and the rate of responding in the positive-reinforcement component declined, as a function of the frequency of point-losses avoided in the avoidance component. The performance of all three subjects conformed to equations proposed by Herrnstein to describe behavior in concurrent schedules. The logarithms of the ratios of the response rates in the two components, and the logarithms of the ratios of the times spent in the two components, were linearly related to the logarithms of the ratios of the frequency of loss avoidance in the avoidance component to the frequency of reinforcement in the positive-reinforcement component. When a changeover delay of 5.0 sec was imposed, the slopes of the linear functions were close to 1.0 in the case of two subjects, whereas the third subject exhibited significant undermatching. For two subjects the changeover delay was then reduced to 2.0 sec; in both cases the slopes of the linear functions were lower than under the 5.0-sec condition. One subject participated in a third phase, in which no changeover delay was imposed; there was a further reduction in the slopes of the linear functions.     

Place information in multidigit number comparison

How do we use place information in a number comparison task involving multidigit numbers? In four experiments, subjects identified stimulus numbers as larger or smaller than the number 5,000 in a choice reaction time task. As the difference between the number of places in the stimulus number and the number of places in the standard decreased, response time and errors significantly increased. When the number of places was held constant, the type of numeric information extracted depended on the value of the standard (5,000 or 5,555). In some cases, irrelevant place information affected choice time.     

Age-related changes in rate of visual information processing

Each of four groups of 12 subjects performed four psychophysical tasks. The age ranges of the four groups were 19-31, 45-57, 58-70, and 71-83 years, respectively. All four tasks required some form of visual information processing: Two were backward-masking tasks; two were temporal-integration tasks. In all four tasks increasing temporal functions over age were obtained, suggesting slower processing rates as age increased. The results support an active processing model of visual perception that interprets duration of visible persistence and duration of interval in which backward masking is effective as indices of the time course of early stages in the processing of stimulus features. The evidences also suggests that backward masking and visible persistence may be mediated by distinct mechanisms that are affected differently by aging processes. A model that conceptualizes the visual system as a multichannel processor is proposed as an explanation for some of the findings.     

Mentally retarded individuals outperform college graduates in judging the nonconservation of space and perimeter

Most adults of average and superior intelligence incorrectly assume that in a two dimensional figure two attributes, area, and perimeter, are locked in a fixed relationship such that if one remains unchanged so does the other. Consequently, when they correctly conserve one attribute during shape transformation, they incorrectly conserve the other. Mentally retarded individuals assume no such fixed relationship but depend exclusively on perceptual information. Although this dependence adversely effects their judgment of conservation, it allows them to correctly judge the changed state of the nonconserved attribute.