The personality theorist Walter Mischel helped define this concept by asking: “When are situations most likely to exert powerful effects and, conversely, when are person variables likely to be most influential?” (Mischel, 1977, p. 346). His answer: Situations are likely to matter most when situations are strong, and conversely, personality is likely to matter most when situations are weak. His reasoning: Strong situations constrain options and provide clear signals about what is expected. Uniform expectancies restrict the degree of behavioral variability across individuals, which in turn limit observed personality-behavior relations. In contrast, behaviors are more likely to reflect relevant personality traits when signals and constraints are weak.
Mischel (1977) used traffic lights and Thematic Apperception Tests (TATs) to illustrate strong and weak situations.
Knowing whether the light is red or green is a better predictor of driver behavior than are personal- ity differences among drivers: In other words, statistical analysis would yield a main effect for the situation and no effect for personality.
Conversely/de modo inverso, a TAT exemplifies a weak situation: A story written in response to TAT cues depends more on the individual storyteller than it does on the individual picture cue; here, statistical analysis should yield a stronger main effect for personality than for situation.