3 studies dealt with the attainment of disjunctive concepts. The positive instances of disjunctive concepts contain either Values A or B, while conjunctive concepts are those whose positive instances contain both A and B. The former are typically more difficult to attain. The 1st experiment showed that training on disjunctive concept problems increases the proportion of Ss who offer a disjunctive concept when a conjunctive concept is also available. The 2nd experiment compared inclusive (A or B or both) and exclusive (A or B but not both) disjunctive problems. The latter were found to be more difficult in terms of the time to solution. (PsycINFO Database Record (c) 2006 APA, all rights reserved)