Effects of peer tutoring and consequences on the math performance of elementary classroom students

The effects of unstructured peer-tutoring procedures on the math performance of fourth- and fifth-grade students were investigated. Students' performances in two daily math sessions, during which they worked problems of the same type and difficulty, were compared. When students tutored each other over the same math problems as they subsequently worked, higher accuracies and rates of performance were associated with the tutored math sessions. The use of consequences for accurate performance seemed to enhance the effects of tutoring on accuracy. The results from an independent-study control condition, which was the same peer-tutoring except that students did not interact with each other, suggested that interactions between students during the tutoring procedure were, in part, responsible for improved accuracy and rate of performance. When students tutored each other over different but related problems to those that they were subsequently asked to solve, accuracies and rates during tutored math sessions were also higher, suggesting the development of generalized skills in solving particular types of math problems.     

Instrumental conditioning of blood pressure elevations in the baboon

Two adult male baboons were surgically prepared with arterial catheters which provided a continuous measure of blood pressure and heart rate. Environmental consequences (food and electric shock) were made contingent upon prespecified increases in diastolic blood pressure levels. Continued exposure to these contingencies resulted in substantial increases in both diastolic and systolic pressures. The results demonstrated that blood pressure changes are highly susceptible to both operant“shaping” and stimulus control procedures and extend the range of instrumental conditioning effects upon the cardiovascular system.     

Illusory contours and stereo depth

A theory for illusory contours, which fill gaps in certain figures, is proposed and subjected to an experimental test. We suggest that nearer masking objects are perceptually postulated to “account” for gaps when these are unlikely. The experiment shows that when stereoscopic depth information incompatible with this “perceptual hypothesis” is presented, the illusory contours are reduced in intensity or disappear.     

On spurious allusions

The criticisms of Walker’ theory by MacLeod, Virsu, and Carpenter are shown to stem from a too simple reading of the text of the theory, a failure to investigate fully the references cited to support their position, and an effort to bolster the theory of lateral inhibition in orientation detectors. The criticisms are shown to misrepresent the experimental data of various reports. Walker’s physiological premises are shown to be sound, and the cases of “contrary evidence” are shown infact to be in agreement with the theory. Lateral inhibition in orientation detectors as an explanation of optical illusions is shown to fail completely to agree with experimental results.     

A revised law of comparative judgment

In contrast to Thurstone's Law of Comparative Judgment, a model in which a comparison pair and its complement are assumed to give rise to two different distributions of differences is considered. The consequences of this revised model on scaling problems is developed.The research in this article was supported jointly by the Army, Navy, and Air Force under contract with the Massachusetts Institute of Technology.     

Separation of data as a principle in factor analysis

Two systems of factor analysis—factoring correlations with units in the diagonal cells and factoring correlations with communalities in the diagonal cells—are considered in relation to the commonly used statistical procedure of separating a set of data (scores) into two or more parts. It is shown that both systems of factor analysis imply the separation of the observed data into two orthogonal parts. The matrices used to achieve the separation differ for the two systems of factor analysis.     

A vigilance task sensitive to the effects of stimulants, hypnotics, and environmental stress: The Scanning Visual Vigilance Test

The Scanning Visual Vigilance Test is a variable-length detection test designed to assess the ability of individuals to maintain visual alertness for sustained periods of time. The test was designed to be sensitive to changes in vigilance produced by subtle variations in performance, such as those produced by low doses of centrally acting food constituents, drugs, or environmental stress. The test has been shown to be sensitive to the effects of stimulants and sedatives, as well as cold stress and sleep loss. It requires the subject to continuously scan a video monitor to detect the occurrence of infrequent stimuli that are difficult to detect. The number of stimuli correctly detected, false alarms, and reaction times are recorded. The stimulus is a small rectangle displayed for 2 sec at random locations on a darker region of a video monitor at random or pseudo-random times. The brightness of the stimulus can be adjusted for each subject individually on an automated threshold detection test. Training and test session length are defined by the experimenter. Hardware requirements are an IBM-compatible personal computer (286 or higher) with a color or grayscale VGA monitor.