The effects of stimulus numerosity,retinal location,and rod contrast on perceived duration of brief visual stimuli

The effects of manipulating three stimulus parameters were determined on a standard perceived duration task using 40- and 70-msec visual stimuli. In Experiment 1, it was found that perceived duration increased with increasing number of target dots but decreased as the area that contained the dots also increased. Experiment 2 examined the effect of varying the retinal location (0, 2, or 4 deg from fovea) of the target dot and found perceived target duration to increase with increasing eccentricity. In Experiment 3, the background luminance for a constant red target was varied so as to alter the scotopic contrast of the target. Perceived duration was minimal for the scotopically matched target and background conditions. The results of all three experiments were discussed in terms of important retinal—and even rod—contributions to tasks of perceived duration.     

Limulus psychophysics: Increment threshold

Prior temporal summation work had indicated that the sensory code for certain behaviors (in bothLimulus and humans) can be understood if one suggests that the central nervous system analyzes the integral of the photoreceptor potential. An independent test of this suggestion is available because (inLimulus) the physiological increment threshold function obtained from the receptor potential integral is inflected, whereas that obtained from the initial transient peak of the receptor potential is not. The behavioral increment threshold function was measured inLimulus and found to be inflected. Fechner’s scaling assumption (that equally detectable stimulus increments are mediated by sensory signals of equal size) was supported by the fact that a theoretical function, which was calculated from the receptor integral intensity-response function by using Fechner’s scaling assumption, was able to fit the behavioral increment threshold function quite well. Furthermore, the variability of the behavioral data was proportional to the receptor integral variability. A seasonal effect was observed: Fall animals were more sensitive and had a higher criterion than winter animals. These findings permit the specification of the rerceptor potential that mediates this particular behavior at threshold: It has a steady-state amplitude of 7 mV in winter and 16 mV in fall. Taken in conjunction with the results of earlier temporal summation work indicating that the threshold receptor potential is 4.5 sec long, this specification implies that at least some behaviors are mediated by large, long sensory signals, which have properties very different from those of small, short signals, particularly with regard to both linearity and their relative dependence on time vs. energy.     

Attractiveness as a biasing factor in the judgments of school psychologists

A sample of 324 practicing school psychologists received a fictitious case study to which was attached a photograph of an attractive boy, an attractive girl, an unattractive boy, or an unattractive girl. Otherwise the case studies were identical. Each psychologist was asked to make several decisions based upon the information provided in the case study. Results of a multivariate analysis of variance indicated that a pupil's attractiveness had a significant effect on the judgments of school psychologists.     

An evaluation of reality orientation therapy

An evaluation was made of reality orientation therapy utilizing 14 male patients with dementias of various types. The therapy is designed to improve memory and reduce confusion in elderly and demented individuals. Utilizing a group comparison with crossover design, it was found that the patients improved significantly over sessions on orientation items actually taught during those sessions. However, no significant improvement was found on a series of generalization items consisting of orientation-related questions that were not asked during sessions. Furthermore, there was no generalization to ward activities. It was noted that individual responses to the treatment were quite varied, and so three cases reflecting highly different responses are presented.Indebtedness is expressed to the Veterans Administration for support of this research.     

Frequency of measurement and data utilization as factors in standardized behavioral assessment of academic skill

A study was conducted to investigate the effects on students' spelling achievement of variations in teacher assessment procedures. Teachers measured student spelling performance at a constant level of task difficulty using different measurement frequencies and different rules to interpret the data. Each teacher wrote two consecutive 3-week goals for improved spelling performance for two sets of 100 spelling words and then measured student performance either daily or weekly by dictating randomly selected words from each 100-word list. Teachers were trained to apply either a predetermined set of decision rules or their own judgment to the data to decide if the spelling program they had implemented for the student was effective. Ineffective programs were changed or modified. Results indicated that daily measurement was significantly more effective than weekly measurement in increasing spelling achievement and that, under certain conditions, decision rules were more effective than teacher judgment in determining when to make program changes or modifications.This research was conducted pursuant to Contract 300-77-0491 between the Bureau of Education for the Handicapped (now called Special Education Programs) and the University of Minnesota Institute for Research on Learning Disabilities.     

PERSONALITY AND ENVIRONMENTAL CORRELATES OF ACADEMIC ACHIEVEMENT IN OJIBWA INDIAN YOUTH*

High School Personality Questionnaire profiles, grades, and boarding home information were obtained for almost the entire Grade 9 and 10 native Indian student population in the districts of Kenora, Rainy River, and Thunder Bay (Ontario, Canada) in order to discover the factors that relate to the high incidence of academic failure among native students. Native Indian youth as a group differed from white population in personality traits, but the lack of a strong correlation between these personality traits and school grades suggests that the personality traits characteristic of an Indian population are not the primary cause of school failure. Students who came from remote reserves were better adjusted than those who lived within driving distance of white settlements and had greater opportunities for acculturation. There was no correlation between school grades and boarding home conditions. Female students showed less variability in personality structure than males, and seemed less affected by changes in culture and boarding home conditions. A comparison of native students in academic and occupational programs revealed some personality differences among males but none among females.     

Identification and classification of characters in two alphabets

Bilingual subjects were presented with pairs of characters drawn from either the English or the Hebrew alphabet. They were asked to indicate whether the two characters belonged to the same alphabet, or whether the two characters denoted the same sound, regardless of whether they belonged to the same alphabet. A model is proposed whereby the two characters are processed in parallel, with characters belonging to a nonnative alphabet requiring more processing time than characters belonging to one's native alphabet. The native-language effect appears to be localized peripherally. The data do not suppott models which categorically place identification before classification or vice versa.This research was supported by United States Public Health Service Grant MH-19705.