The vehicle McClelland employed to establish the presence of an achievement motive was the type of fantasy a person expressed on the Thematic Apperception Test (TAT), developed by Christiana Morgan and Henry Murray, who note in Explorations in Personality that "...when a person interprets an ambiguous social situation he is apt to expose his own personality as much as the phenomenon to which he is attending... Each picture should suggest some critical situation and be effective in evoking a fantasy relating to it" (p531). The test is composed of a series of pictures that subjects are asked to interpret and describe to the psychologist. The TAT has been widely used to support assessment of needs and motives. The procedure in McClelland's initial investigation was to arouse in the test audience a concern with their achievement. A control group was used in which arousal was omitted. In the course of this experiment, McClelland discovered through analyzing the stories on the TAT that initial arousal was not necessary. Instead, members of the control group — individuals who had had no prior arousal — demonstrated significant differences in their stories, some writing stories with a high achievement content and some submitting stories with a low achievement content. Using results based on the Thematic Apperception Test, McClelland demonstrated that individuals in a society can be