Although a lot of data on the psychological characteristics of children having learning disabilities have been gathered, not very much has been done to discover the underlying mechanisms, processes, or phenomenon of learning disability. Without more investigations which attempt to get at these, we will continue to be at a loss to prescribe effective methods for improving the health, education, employment opportunity, and social health of these children. A homomorphic psychometric model has been proposed to show the integrative functions and relationships between and among psychometric measures of learning ability, aptitude, and/or achievement. If the proposed homomorphic psychometric model can be used to demonstrate interrelationships among psychometric measurements as do the cognitive structures of learning theorists and as do neuron during interfacilitation, then a systematic study of the distribution and interrelationships of such measures among high- and low-achieving children might offer insights into means by which each group proceeds to solve educational tasks. In a recent study an attempt was made to discover the differences between the cognitive functions of 109 high-and low-achieving eighth grade students. Six tests of cognitive ability and eight subtests of the Iowa Tests of Basic Skills were used in the analyses. (Author/JM)