Investigation of the Cognitive Mechanisms of Same and Different Judgments

Abstract

The Same-Different task is an experimental paradigm in which a stimulus pair is presented in succession to a participant whose task is to determine if the stimuli are Same or Different. Typical results show that participants tend to be quicker to respond Same then they are to respond Different. Since the 1960s, many models were proposed to explain this effect, but none has yielded conclusive evidence. The objective of this thesis is to test these models with three experiments by focusing on three research questions: 1) what is the source of the effect, the participant or the stimuli?; 2) what is the organization of the cognitive mechanisms underlying the task?; and 3) what is the effect of the number of attributes on the processing capacity? Results show that the fast-same effect stems from the characteristics of the stimuli rather than an inherent preference for sameness. They also show that the cognitive architecture underlying the task is serial, but that it does not seem to explain solely the fast-same effect. Indeed, the fast-same effect seems to be rather caused by a more efficient processing of Same stimuli in the first 500 ms of the treatment compared to Different stimuli.