The purposes of this study were to determine if communalities exist among three types of human concept attainment tasks, and, if so, to relate the factors to previously identified reference factors. A battery of 16 paper-and-pencil reference tests, representing seven previously identified factors, was administered to 119 male ninth-grade students. The seven factors or ability measures represented were flexibility of closure, induction, associative memory, number facility, general reasoning, syllogistic reasoning, and verbal comprehension. After the reference battery was given, subjects were tested on 12 concepts that represented three types of tasks: nonverbal concepts restricted by the attributes of the stimuli (card sort tasks), nonverbal concepts not restricted by the attributes of the stimuli (Goldstein's tasks), and verbal concepts (Allison's tasks). It was concluded that (a) communalities do exist between different concept attainment tasks; however, these communalities are restrictive and do not include all tasks within the types defined by this study. Therefore, further analyses of the relationships between concept attainment tasks will be necessary before the results of experiments can be compared if different types of concept attainment tasks are used. (b) Certain reference test abilities are related to certain concept attainment abilities. (c) Nonsolvers, in an attempt to solve concept attainment tasks, use reference abilities that solvers do not use. The reference abilities that nonsolvers use vary with the concept attainment task they are trying to attain.