Abstract
Purpose: Previous research suggests that subjects are around 90ms faster detecting familiar letter presented unilaterally versus. Here we examine the question of whether previous knowledge of the stimulus class affects the within-field advantage.
Method: Six subjects, 3 with no knowledge of the Arabic alphabet, 3 fluent in both the Arabic and Western alphabet, were tested in detecting repetitions of Western or Arabic letters via blocked design. Subjects indicated if there was a repetition of any two of four presented characters. Stimuli were placed in each quadrant. A repetition was present on half the trials and was either unilateral (the two repeated items within one visual hemifield, right or left), or bilateral (one of the two repeated items in each field).
Results: When averaged together subjects were significantly faster at detecting repetitions for both that occurred within versus across visual fields for both Western characters (92ms, p < 0.00) and Arabic characters (70ms, p < 0.00). Subjects only familiar with the Western alphabet had a 76ms within field advantage for Western characters (p <0.05). For Arabic characters the 68ms advantage was not significant. Also these subjects were on average 150ms faster at detecting Western versus Arabic repetitions. Subjects familiar with both alphabets showed similar mean RTs and a significant with-in field advantage for both types of characters.
Conclusion: These results suggest: 1) familiarity modulates the detection of repetitions, as western subjects were faster overall in detecting repetitions of familiar characters and 2) the within-field advantage may rely previous experience with the stimulus class.
Research supported by NSF graduate fellowship to SJB.