The “magic” paradigm revisited

The “magic” paradigm was devised to assess conservation of number in young children. Previous results with the paradigm have suggested that children acquire the ability to conserve number by 3 years of age. Because these results indicate a very precocious development of number conservation relative to performance on the classic conservation task, a comparison of these two procedures was made. Several differences which might account for the superior performance with the magic paradigm were noted: The arrays are presented successively rather than simultaneously, the arrays are presented side by side rather than parallel to one another, and the displacement is performed surreptitiously rather than openly. In the present research the magic paradigm was modified in several steps so that these differences between procedures were removed. None of the changes had an impact on the performance of 3-year-olds. It was concluded that insofar as small numbers are concerned, young children treat displacement as irrelevant to number. In regard to the question of whether young children are capable of conserving small numbers, it was concluded that no answer can be given. Basically, the problem is that we lack sufficient information on how young children solve the magic paradigm.     

Detection of informational constraints related to multi-variate visual displays

A contingent uncertainty of one bit is perceptible when imposed upon a combination of two binary-coded visual display variables, but not when imposed upon a combination of three variables. Why? The limitation may be sought in the average amount of the constraint, in the form of the constraint, or in the particular selection of display variables. Tests were carried out in which apparently equivalent informational constraints were imposed upon a single display variable. Such constraints were highly discriminable. Further tests reveal that the limiting feature for the detection of multi-variate constraints is probably the mean constraint level, averaged over all display elements, rather than the constraint level imposed upon the constrained display elements.     

Information underload: Recognition of slowly-presented alphabetic characters

The accuracy of identification of alphabetic letters was examined under three experimental procedures: slowly plotting all of the dots associated with a given display of letters in their correct spatial positions, but in a random temporal order; rapidly plotting one half of the dots associated with a display, and after a variable delay, rapidly plotting the other half of the dots; and rapidly plotting only a fraction of the total number of dots associated with the display. The accuracy of identification suffers as the rate of plotting is decreased and as the interval between the successive fields is increased. Therefore, a failure of spatial-temporal integration is inferred. The results of the separate procedures are partially consistent with an interpretation of a discrete, non-synchronized perceptual moment of 120–150 msec duration, assuming no accumulation of information across successive moments.     

Bias functions and operating characteristics of rats discriminating auditory stimuli

Rats were trained to discriminate between two bursts of random noise that differed in intensity. In a two-lever, discrete-trial procedure, correct responses were reinforced with brain stimulation, and incorrect responses produced timeout. Responding was studied as a function of the decibel difference between the stimuli, the probabilities of presenting the stimuli, the relative duration of timeout consequent upon the two types of incorrect responses, and the absolute duration of timeout consequent upon incorrect responses. The results showed that the distribution of responses between the two levers depended upon the stimulus probabilities, but were independent of either the absolute or relative durations of timeout. When the stimulus probabilities were varied, the response probabilities did not match the stimulus probabilities; when the relative durations of timeout were varied, the animals did not obtain the maximum rate of reinforcement per unit time. Instead, the animals distributed their responses so as to obtain the maximum number of reinforcements at each level of discrimination. In addition, the level of discrimination increased as a function of the decibel difference between the stimuli.     

A method for clustering eigenvalues

A method of computing communalities is presented which attempts to cluster eigenvalues about zero. Results are exhibited which show reduction of rank using computed communalities.This paper is based on work performed under Contract AF 30(602)-3300 monitored for the U. S. Air Force by Mr. Rocco Iuorno, Rome Air Development Center. The use, under the above contract, of the IBM 7094 computer located at Aeronautical Systems Division, Wright-Patterson Air Force Base, is gratefully acknowledged. Permission is granted for reproduction, translation, publication, use, and disposal in whole and in part by or for the United States Government.     

Evaluation of a preventive intervention for a self-selected subpopulation of children

Evaluated an experimental preventive intervention developed for children who perceived their parents as problem drinkers. The 8-session program was designed to improve children's coping, self-esteem, and social competence, and modify alcohol expectancies which were specified as mediators of the effects of parental alcohol abuse on child mental health. Participants were 271 self-selected 4th-, 5th-, and 6th-grade students in 13 schools. The children were randomly assigned to treatment or delayed treatment conditions and the program was given to three successive cohorts of students. A meta-analysis across three different cohorts indicated significant program effects to improve knowledge of the program content and the use of support- and emotion-focused coping behaviors for the full sample. A slightly stronger range of effects was found for a high-risk subsample. This research was funded by the National Institute of Mental Health Grant P50-MH39246 to support a Preventive Intervention Research Center and Prevention Training Grant T32-MH18387-02.     

Differential thresholds for limb movement measured using adaptive techniques.

Differential thresholds for limb movement were measured in 10 subjects, using the transformed up-down procedure. Subjects were required to indicate which of two random displacement perturbations delivered to their forearms had the larger standard deviation (SD). The SD of the reference signal was fixed for each experimental condition at one of seven values ranging from 0.05 to 3.2 mm. THe SD of the other signal varied depending on the subject's response. Using this procedure, the differential threshold for limb movement was calculated to be 8%, which is very similar to the thresholds estimated previously for changes in limb position (9%) and force (7%). The sensitivity of the human proprioceptive system to changes in limb displacement was much greater than anticipated, with subjects being able to resolve a 5-microns difference between two perturbations delivered to their arms.