Ambiguity and the abstract tact: A signal detection analysis

Four observers who had completed a formal course in projective test techniques were asked to discriminate House-Tree-Person (H-T-P) drawings made by psychiatric patients from those made by nonpatients. A 4.5 kHz tone presentation was made contingent upon one of two classes of errors, failure-to-tact errors or false-tact errors, depending on the experimental condition in effect. The observers were instructed that a 2 second tone presentation would occur each time the experimenters disagreed with the observer. The duration of tone presentation was variable depending upon the number of disagreements that occurred after blocks of either 5 or 10 responses. All observers showed some degree of abstractional control by the set of patient drawings. The likelihood of a correct tact was shown to vary as a function of the consequences contingent upon each type of error for 3 of the 4 observers. However, the discriminability index d'e remained unchanged for all observers throughout all experimental conditions.