Exploratory Experiments in Color Discrimination

Gesell, A., Amatruda, C. S., Castner, B. M., &; Thompson, H. Biographies of Child Development. New York: Harper, 1939. Pp. 328.) Reviewed by Livingston Welch

Muenzinger, K. F. Psychology: The Science of Behavior. Denver: World Press, 1940. Pp. XIII + 343.) Reviewed by Egon Brunswik     

The Roles of Explanation and Feedback in False Belief Understanding: A Microgenetic Analysis

The authors examined effects of feedback and explanation on false belief performance. Thirty-three children (42–54 months; 15 girls, 18 boys) were randomly assigned to four treatment conditions: explanation, feedback, feedback researcher explains, and feedback child explains. Children completed false belief tasks during pretraining, 8 training sessions, and posttraining across 6 weeks. Language comprehension was assessed at pretraining. The authors hypothesized that children would improve most when training involved feedback and explanation. Generalized estimating equations modeling was used to analyze the data. Children who received feedback and generated explanations for characters’ false beliefs improved across training sessions more so than children in other conditions. Children's explanations for false beliefs also were explored. Implications of the findings are discussed.     

Worry and Sleep Length Revisited: Worry,Sleep Length,and Sleep Disturbance Ascribed to Worry

The author administered university students (N = 222; 152 women, 70 men) the Worry Domains Questionnaire (F. Tallis, G. C. L. Davey, & A. Bond, 1994) and a newly constructed scale (the Sleep Disturbance Ascribed to Worry Scale) to measure sleep disturbance attributed to worry. To revisit previous studies (i.e., E. Hartmann, F. Baekeland, & G. R. Zwilling, 1972; S. J. H. McCann & L. L. Stewin, 1988) that suggested that sleep length was positively related to worry, the author also asked the students a question about habitual sleep length. The results indicated that worry and sleep disturbance attributed to worry were negatively related to sleep length. A regression analysis revealed that worry was significantly negatively related to habitual sleep length irrespective of sleep disturbance ascribed to worry.     

Preliminary Observations on Play Behavior in Puppies

Previous research suggested that the experimenter variable in conservation assessment procedures has not been adequately studied. This experiment investigated the effect of sex of experimenter on length conservation responses in second-grade subjects under group testing procedures. Results of contingency table analysis of observed frequencies suggested that there are significantly more operational conservers under female test administration than under male test administration. Further analysis revealed no significant difference in the number of operational conservers for male and female Ss with either male or female examiners. The sex of experimenter variable does appear to be an important factor in conservation assessment at the lower elementary level.     

Prior distributions for random choice structures

We study various axioms of discrete probabilistic choice, measuring how restrictive they are, both alone and in the presence of other axioms, given a specific class of prior distributions over a complete collection of finite choice probabilities. We do this by using Monte Carlo simulation to compute, for a range of prior distributions, probabilities that various simple and compound axioms hold. For example, the probability of the triangle inequality is usually many orders of magnitude higher than the probability of random utility. While neither the triangle inequality nor weak stochastic transitivity imply the other, the conditional probability that one holds given the other holds is greater than the marginal probability, for all priors in the class we consider. The reciprocal of the prior probability that an axiom holds is an upper bound on the Bayes factor in favor of a restricted model, in which the axiom holds, against an unrestricted model. The relatively high prior probability of the triangle inequality limits the degree of support that data from a single decision maker can provide in its favor. The much lower probability of random utility implies that the Bayes factor in favor of it can be much higher, for suitable data.     

Coordination of Grip Configurations as a Function of Force Output

In this investigation, the authors examined the coordination and control of force production by the digits of the hand as a function of criterion force level and grip configuration. Each adult participant (N = 6: 3 men and 3 women) was required to place the thumb and a finger (or fingers) upon load cells that were fixed to a grasping apparatus that was clamped to a table. In the task, participants had to match a criterion continuous constant total force level displayed on a computer screen. There were 10 trials at each grip configuration and criterion force level combination on each of 3 consecutive days. The results showed that (a) different grip configurations minimized error at each force level; (b) there was a specific digit pairing within a given grip configuration that produced the highest correlation of force output; (c) the correlation between the force output of digits generally increased at higher force levels; (d) error was reduced at each force level and grip configuration over the practice period; and (e) the organization of the force output of each digit varied as a function of digit, force level, grip configuration, and practice. The findings are consistent with the hypothesis that coordination of the digits in prehension is reflective of an adaptive, task-specific solution that is modified with practice.     

Spinal Cord Circuits

Over the past decade, research at three different levels of sensorimotor control has revealed a degree of complexity that challenges traditional hypotheses regarding servocontrol of individual muscles: (a) The connectivity of spinal circuits is much more divergent and convergent than expected. (b) The normal and reflex-induced recruitment of individual muscles and compartments of muscles is more finely controlled than was noted previously. (c) The mechanical interactions among linked skeletal segments and their often multiarticular muscles are neither simple nor intuitively obvious. We have developed a mathematical model of the cat hind limb that permits us to examine the influence of individual muscles on posture and gait. We have used linear quadratic control theory to predict the optimal distribution of feedback from a hypothetical set of proprioceptors, given different assumptions about the behavioral goals of the animal. The changes in these predictions that result from changes in the structure and control objectives of the model may provide insights into the functions actually performed by the various circuits in the spinal cord.