Journal of Experimental Social Psychology vol:49 pages:1159-1167
Two studies were conducted to test the predictions of a multi-component model of distinctiveness-based illusory
correlation (IC) regarding the use of episodic and evaluative information in the production of the phenomenon.
Extending on the standard paradigm, participants were presented with 4 groups decreasing in size, but all
exhibiting the same ratio of positive to negative behaviours. Study 1 (N = 75) speciﬁcally tested the role of
group size and distinctiveness, by including a zero-frequency cell in the design. Consistent with predictions
drawn from the proposed model, with decreasing group size, the magnitude of the IC effect showed a linear increase in judgments thought to be based on evaluative information. In Study 2 (N = 43), a number of changes
were introduced to a group assignment task (double presentation, inclusion of decoys) that allowed a more rigorous test of the predicted item-speciﬁc memory effects. In addition, a new multilevel, mixed logistic regression
approach to signal-detection type analysis was used, providing a more ﬂexible and reliable analysis than previously. Again, with decreasing group size, IC effects showed the predicted monotonic increase on the measures
(group assignment frequencies, likability ratings) thought to be dependent on evaluative information. At the
same time, measures thought to be based on episodic information (free recall and group assignment accuracy)
partly revealed the predicted enhanced episodic memory for smaller groups and negative items, while also
supporting a distinctiveness-based approach. Additional analysis revealed that the pattern of results for judgments though to be based on evaluative information was independent of interpersonal variation in behavioral
memory, as predicted by the multi-component model, and in contrast to predictions of the competing models.
The results are discussed in terms of the implications of the ﬁndings for the proposed mechanisms of illusory