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Abstract
This study investigated whether two different neural systems influenced performance in an immediate visual recognition, i.e. visual same/different task. An observer had to respond rapidly whether a test consonant had just appeared in the study string by pressing one of two response keys, labeled same and different. When the same response was assigned to the response key on the right, there was no effect of study-string position on target response time (RT), indicating that the test item was not compared with the study string. When the different response was assigned to the response key on the right, same RT was an increasing function of the left-to-right position of a target in the study string and different RT was slower than same RT, indicating that during test the study string was compared with the test item. Functional magnetic resonance imaging confirmed that the caudate and left hippocampus were more active when the different response was assigned to the right key but the right hippocampus was more active when the same response was assigned to the right key. Therefore, two different computational processes are performed by two different brain systems depending on whether the same or different response is assigned to the right response key.
Keywords Eye Movements · Mechanisms · Neural mechanisms · Response time models
Introduction
A long-standing paradox in the study of visual recognition is that in a same/different visual recognition task in which response time (RT) was the dependent measure, the results indicated that two different computational processes were involved in the generation of same versus different responses (Bamber, 1969; Proctor & Healy, 1987). In the same/different task (Bamber, 1969; Proctor & Healy, 1987; Sinha & Glass, 2017), a four-consonant, study string was compared with a four-consonant, test string and participants responded whether the test string was the same as or different from the study string. RT for different responses was a function of the left-to-right location of the first difference between study string and test string, indicating the involvement of the study string in generation of different responses, most likely through left to right comparison with the test string. However, RT for same responses was shorter than the shortest different RT, which was for test strings that differed from the...