Research supported by a grant from the College of Social and Behavioral Sciences, Ohio State University, Columbus, Ohio. Reprints of article available from J. Dennis Nolan, Department of Psychology, Ohio State University, Columbus, Ohio, 43210. (DS)

Three papers--comments, a reply to comments, and a rejoinder--discussing a conclusion about the nature of general intelligence based on the size loadings of a psychomotor test of discrimination reaction time are presented. The use of Spearman's "g" is the center of the controversy. (TJH)

A probabilistic item response theory (IRT) model is developed for pair-comparison design in which the unfolding principle governing the choice process uses a discriminant process analogous to Thurstone's Law of Comparative Judgment. A simulation study demonstrates the feasibility of estimation, and two examples illustrate the implications for…

Review of reversal learning data obtained from Ss of various developmental phases suggested that overtraining increases perseveration in pre-school children, and decrease perseveration in older (e.g., 1st grade) children. The present experiment tested this apparent trend. Children of two age groups (X = 4 yrs., 4 mos., vs. X = 6 yrs., 5 mos.)…

Simple and complex learning and problem solving situations were employed with mentally retarded children and adults. In the Rotation-Discrimination Complex and the Size-Discrimination Simple experiments, upper and lower test achievement subgroups were subjected to two basic types of visual discrimination at different levels of task complexity.…

AN INSTRUMENT FOR MEASURING VISUAL DISCRIMINATION ABILITY WITHOUT CONFOUNDING VARIABLES OF MOTOR SKILLS HAS BEEN CONSTRUCTED. TO AVOID THE EYE-HAND COORDINATION USUALLY REQUIRED ON THESE TESTS, A SELECTION, RATHER THAN A DRAWING, RESPONSE WAS DEVELOPED. THIS TEST, THE UNIVERSITY OF CALIFORNIA AT LOS ANGELES DISCRIMINATION INVENTORY (VDI), CONSISTS…