Parallel discrimination of subjective contours defined by offset gratings

Recent physiological studies (von der Heydt & Peterhans, 1989) suggest that the orientation of subjective contours is encoded very early in the visual system (V2 in monkey). This result is seemingly at odds with existing psychophysical data which suggest that the detection of subjective contours involves selective attention. It is argued that certain subjective contours are registered in a reflexive (bottom-up) manner by the visual system but that selective attention may be needed to gain access to this representation. To assess this suggestion, a visual-search task was used in which subjects were to detect the presence of a horizontal (vertical) subjective contour (defined by offset gratings) in a variable number of vertical (horizontal) subjective contours (also defined by offset gratings). When there were no competing organizations within the display, detection was indeed independent of the number of nontarget distractors, that is, selective attention was unnecessary. In a second experiment, we found that a curved form (a crescent defined by subjective contours) was easier to detect in a background of vertical bars (also defined by subjective contours) than vice versa, namely, a search asymmetry paralleling those found by Treisman and Gormican (1988). A final experiment showed that when the horizontal and vertical bars of the first experiment formed textured regions, they could be discriminated at very brief display durations (30–120 msec), However, when the line terminations aligned along the subjective contour were tapered rather than abrupt, discrimination dropped off with the degree of tapering. The latter result is consistent with the assumption that the registration of subjective contours in V2 involves the integration of responses from aligned, end-stopped cells found in VI (von der Heydt & Peterhans, 1989).     

Blocking Effects in Two-Choice Discrimination Tasks in Rhesus Monkeys Macaca Mulatta

The Psychological Record - The present experiments investigated blocking effects in rhesus monkeys (Macaca mulatta) in a discrimination learning paradigm using a single stimulus modality. Two...     

Relationship between two nontraditional procedures for assessing speech-sound discrimination

Test of speech-sound discrimination are used by special educators, reading specialists and speech-language pathologists in assessing children's ability to differentiate between speech sounds occurring in standard English. Such tests are important in determining if speech-sound articulation errors are caused by difficulty in making such differentiations. However, during the past 10 years, these tests have been criticized on the basis of their reliability and validity. The purpose of this study was to examine the use of two alternative methods of assessing speech-sound discrimination with a school-aged population to determine if they elicited responses in a similar manner.     

Throwing action from full-cue and motion-only video-models of an arm movement sequence

The purpose of this study was to determine whether videotaped demonstrations of an action which displayed only the motion pattern of a model's limb as compared with one which showed both form and motion provide sufficient information for modelling a given pattern of movement. Video-demonstrations of an arm-movement sequence which ended with a throwing action were shown to adult subjects whose task was to model precisely what they saw. Each demonstration lasted 6 sec. and was shown 6 times. It portrayed the arm of a model, who held a small ball, performing a sequence of movements (flexion and extension of the elbow) which ended in the ball being thrown about 2.5 m with a 'darts-style' action. Three types of demonstration were presented: one showed the whole arm in dark clothing against a light-coloured background, another showed the arm as the relative motion of patches of light situated at the shoulder, elbow, and wrist joints, and the third showed the arm as the relative motion of the upper and lower segments of the arm represented by strips of light-reflectant material. These were the stimuli for the between-groups experimental conditions. Goniometry techniques were used to compare the performance of subjects relative to the model. Analysis showed that the order of the preparatory sequence was correctly produced after 4 trials under all conditions. Range of arm movement in projecting the ball closely approximated that of the model after 4 trials in all conditions. The time taken for the arm to project the ball remained constant across trials under all conditions and was always slower than the demonstrated cadence.(ABSTRACT TRUNCATED AT 250 WORDS)     

Common problems and coping strategies I: Findings with normal adolescents

This study investigated problems commonly experienced by adolescents and the strategies they use to cope with these events. Coping strategies were examined across the subjects' omotional state and their evaluation of the problem. In general, adolescents reported four common Stressors that were similar across age groups and gender. However, males differed from females in the frequency of these problems. Further, while the Stressors were similar, the frequency with which the coping strategies were employed and the efficacy ascribed to them differed across sex and across problem type. These findings are discussed in terms of the stress and coping literature with adults and the implications for clinical assessment and treatment of adolescents.     

Research on black women college administrators: Descriptive and interview data

The article summarizes the results of a survey and follow-up interview of black women college administrators, at predominantly white colleges, in selected positions, such as president, vice-president, dean, director, department chairperson, and the assistants and/or associates to the aforementioned positions. The author gives a profile of a middle-management group of women who are at different colleges in the City University of New York system. Also included are a review of the literature and recommendations for both the University and black women seeking careers in college administration.     

DISTRACTION: ITS UTILIZATION AND EFFICACY WITH CHILDREN UNDERGOING DENTAL TREATMENT

We investigated the utilization and efficacy of distraction in reducing the anxious and disruptive behavior of 4 children undergoing dental treatment. During the distraction procedure, the children were shown a poster and told a story about it during dental treatment. They earned a prize if they attended to the poster and story and could correctly answer questions about them following each intervention visit. The children's disruptive behavior was assessed via direct observation, and results were analyzed within a multiple baseline design. The children exhibited high levels of anxious and disruptive behavior across baseline visits, regardless of the length of time in treatment or number of visits. Anxious and disruptive behavior decreased upon introduction of the intervention for all children. This was accompanied by the children meeting the criterion for correct answers on the distraction quiz. However, 2 of the children demonstrated an increase in their anxious and disruptive behavior across intervention visits. Results are discussed in terms of the need to evaluate treatment strategies that promote maintenance as well as initial changes.     

PROMOTING SAFETY BELT USE WITH TRAFFIC SIGNS AND PROMPTERS

Two studies were conducted examining the stimulus-control effects of conventional traffic signs as prompts for motor vehicle driver safety belt use. Following pilot research which suggested that a traffic sign reading “Fasten Safety Belt” posted at a parking lot exit was effective in producing small increases in safety belt use, Study I demonstrated the superiority of having human prompters display such signs compared to simply posting the signs. Study II replicated the findings of Study I and found that posted signs became more effective in prompting safety belt use if simple posting was preceded by a period involving human prompters who displayed the signs. The results bear upon the development of more effective use of traffic signs in promoting safety belt use and in viewing such use as an instance of rule-governed behavior.     

Interactive braille output for blind computer users

Blind readers were tested using two methods of reading text displayed by an Apple microcomputer. The first method employed an Optacon system, a device that displays tactile representations of single characters, and the second used an interactive single electronic braille cell that displayed grade 1 braille characters. The results demonstrated no difference in accuracy or reading speed between these two methods. Thus, the serial presentation of braille characters at a single position appears to be a viable method of information transfer between computers and braille readers.     

Iterative least squares estimates of communality: Initial estimate need not affect stabilized value

A common criticism of iterative least squares estimates of communality is that method of initial estimation may influence stabilized values. As little systematic research on this topic has been performed, the criticism appears to be based on cumulated experience with empirical data sets. In the present paper, two studies are reported in which four types of initial estimate (unities, squared multiple correlations, highestr, and zeroes) and four levels of convergence criterion were employed using four widely available computer packages (BMDP, SAS, SPSS, and SOUPAC). The results suggest that initial estimates have no effect on stabilized communality estimates when a stringent criterion for convergence is used, whereas initial estimates appear to affect stabilized values employing rather gross convergence criteria. There were no differences among the four computer packages for matrices without Heywood cases.