The Effects-of Repeatedly Retesting the Same Group on the Same Intelligence Test: II High Grade Mental Defectives

Twelve mentally-defective schoolboys between 14 and 16 years of age took an intelligence test (AH 4) once a week, ten times. They took also Progressive Matrices once, after they had finished the AH 4 testing. Subjects of low intelligence were chosen in order to throw some light on the findings of a previous experiment on repeated retesting, in which the subjects were intelligent adults. The main aims of the schoolboy enquiry were to ascertain how far the flattening of the progress curves observed in the earlier enquiry was due to the artificial “ceiling” imposed and how far the part played by variation within the individuals varies with the level of intelligence of the group. The mentally-defective subjects showed a gradual improvement in test performance with little sign of flattening towards the end; their individual progress curves were far less smooth than had been those of the more intelligent subjects. Other findings included relatively high proficiency on the diagrammatic part of the test, as opposed to the verbal and numerical, and some transfer of training from AH 4 to Progressive Matrices.