1. Discussion  Experiments 1, 2, and 3 showed that the lag effect only occurred for 5-letter words that were included in lists with longer words. The longer words masked them, resulting in poor detection and a high proportion of guessed responses. An artifact of the design was that targets tended to appear near the beginning and end of the list. This was reflected in the response bias, which produced the lag effect.  Experiments 4, and 5 showed that when all letters were presented in upper case, the different advantage occurred for all vowels. Experiment 6 showed that when the target vowel appeared once in each case, the different advantage occurred for vowels whose upper and lower case forms were the same, i.e., O-u was detected more often than O-o, but not for vowels whose upper and lower case forms were different, i.e., A-e was not detected more often than A-a. One possible explanation is fatigue of specific feature detectors raises the detection threshold. An Alternative Definition of Repetition Blindness During Rapid Serial Visual Presentation a repeated item is sometimes less likely to be detected than an unrepeated item. This effect is called Repetition Blindness. The purpose of this study is to determine the cause of repetition blindness. General Purpose: During Rapid Serial Visual Presentation a repeated item is sometimes less likely to be detected than an unrepeated item. This effect is called Repetition Blindness. The purpose of this study is to determine the cause of repetition blindness. Experiments 1, 2, and 3 Experiments 1, 2, and 3 Purpose: Experiments 1, 2, & 3. Kanwisher (1987) found that detection of a repeated target increased when the number of intervening items between repetitions increased from 1 through 4 (Table 1). These experiments examined this lag effect. Design * 42 different 7- word lists * 14 R1 (1 st instance of repeated word) and R2 (2 nd instance of repeated word) pairings ~ 1-3, 1-4, 1-5, 1-6, 2-4, 2-5, 2-6, 2-7, 3-5, 3-6, 3-7, 3-8, 4-7, and 5-7 * 50 subjects see each pairing 3 times Hanin Rashid Advisors: Arnold Glass and Gary Brill Hanin Rashid Advisors: Arnold Glass and Gary Brill Experiments 4, 5, and 6 Experiments 4, 5, and 6 Purpose: To test Kanwisher’s 1996 experiment which she indicated repetition blindness results rested on and to determine whether minor variations in the instructions would relinquish this effect Design Design 360 11 letter lists *120 have one vowel *120 have the same vowel twice, one or four positions apart *120 have two different vowels, one or four positions apart *15 subjects Comparison of Kanwisher (1987) with Experiments 1, 2, and, 3. The Interaction Between the Effects of Word Length and Lag on Hit Rate for Detection of a Repeated Word in Experiment 3 Hit Rate for Detection of a Repeated Vowel Procedure Determine which word was repeated 250 ms 250 ms 250 ms 250 ms 250 ms 250 ms ******* HIP sat man ALL bat 250 ms 250 ms 250 ms 250 ms 250 ms 250 ms 250 ms 250 ms CAN all fat %%% CAN all fat %%%____________________________ Rate confidence: “1” if sure, “2” if probably correct, “3” if guessing _____________________________ Experiment 1: 3- letter words Experiment 2: 5- letter words Experiment 3: 5, 6, and 7- letter words Procedure Procedure Determine whether 1 or 2 vowels were presented 145 ms 120 ms 120 ms 120 ms 120 ms 120ms 120 ms 120 ms 120 ms + Z n O P R e w J 120 ms 120 ms 120 ms 225 ms 120 ms 120 ms 120 ms 225 ms G F v ###### G F v ######__________________________________________ Rate confidence: “1” if sure, “2” if probably correct, “3” if guessing __________________________________________________ Experiment 4: Target constructed by sampling from two specified vowels with replacement. Experiment 5:   In condition 1: The subject was alerted to what the second target letter would be, if there was one. Here is an example of the instructions we gave to the subjects in condition 1 for a repeated target: “On the next trial, the list you will see will be all consonants, except for one or two vowels. The list will contain a U, followed somewhere in the list by either no other vowel, or another U.”   In condition 2: There were also "same" and "non-identical" repetitions, and the subject was told that it could be either one of two target letters. Here is an example of the instructions we gave to subjects for a non- identical target: “On the next trial, the list you will see will be all consonants, except for one or two vowels. The list will contain a U, followed somewhere in the list by either no other vowel, an A or another U.” Experiment 6: Targets were only A, E, O, and U. The same two conditions are experiment 5 Target Position 2-4 5-7 2-5 4-7 2-6 3-7 2-7 Lag1234 Linear trend Experimenter Word Length SOA Kanwisher5,6,7 117 ms 35434855p<.05 Experiment 13 150 ms 7872 76p=.805 Experiment 25 150 ms 69767578p=.257 Experiment 35,6,7 150 ms 53545963p=.02 Word LengthLag 1234 542495864 663585963 758 63 Experiment, Condition Same VowelDifferent Vowel 4.70.89 5,1.72.90 5,2.81.94 6.85.98 Case SimilarityCondition 1Condition 2 Same O-o, U-u.76.97 Different A-a E-e.94.98 Effect of Upper-Lower Case Similarity on Hit Rate for Detection of a Repeated Vowel in Experiment