1. Temporary suppression of visual processing in an RSVP task: an attention blink? By Raymond, Shapiro, & Arnell JEP:HPP

2. Attention blink phenomenon What is it? Why does it occur? What can we say about the mechanism of human attention from this? How does this cognitive phenomenon help understand our everyday activities?

3. Attention blink experiment Coglab CD You see a stream of 19 letters (110ms for each letter). After seeing the stream, –Press J if J is present –Press K if K is present –Press J&K if both J and K are present. –Press nothing if you see neither J nor K.

4. Manipulations Presence / absence –In some trials, J and K are present –In some trials, only J is present –In some trials, only K is present J-K separation –In some trials, 0, 2, 4, 6, and 8 letters separated J and K

5. My results

6. What do this result mean? Why is it so difficult when J & K are separated only by a few letters? What caused this “blink”?

7. Raymond et al. Exp. 1 –Stimuli Randomly ordered streams of letters (11 letters in one sequence) –Task: Identify the white target letter embedded in a stream of black letters, and identify the three letters presented immediately after the target letter. –Subjects: 5 subjects

8. Procedure: 90 RSVP trials were given to each subject. –Each letter was presented for 15 ms with an inter-stimulius interval (ISI) of 75ms. –The target letter was randomly selected. –Ss were instructed to report the name of the white letter (the first target) and the names of the next three letters.

10. Results Results: –Those letters that followed immediately after the target were rarely reported. –The letters that came +5 or more after the target were often reported.

12. What are possible explanations? The task was too difficult – you had to report actual letters –Is this due to memory defect? (you forget the letters) –Is this due to a sensory factor (e.g., masking effect)?

13. Exp. 2 Task: –The target and probe letters were specified before the experiment. –Each letter was presented for 15 ms with an inter-stimulius interval (ISI) of 75ms. = Exp. 1

14. Manipulations Experimental condition: Ss were asked to identify a white letter (target) embedded in a letter stream of black letters, and subsequently to respond if a X (probe letter) had been presented or not. Control condition: Ss did not need to report the white target letter, but just indicated whether a probe X had been present or not some time after the target white letter was shown.

15. Participants –10 subjects, 180 trials/subject. Design –90 trials  a probe was present; –90 trials  a probe was absent –the probe was presented at each of the 9 position 10 times.

16. E.g., target X; Probe Y –0 separation ( -- XY ---) –1 separation ( -- X-Y---) –2 separation (-- X- -Y--) –3 separation (-- X- - - Y --) ….

17. Results the post target deficit effect was observed only in the experimental condition but not in the control condition. Not a sensory mechanism, but an attentional mechanism is responsible for the post target deficit effect. It is not a memory factor, because the target and probe letters were specified prior to the experiment.

18. Exp. 3 Goal and manipulations The blank interval was inserted between the white target letter and the probe letter at varying time intervals (0, 90, 180, 270ms).

19. Logic: Time-related or event-related? –If the posttarget deficit is time-related, attenuated (gradual decrements of the posttarget deficit) time-dependent deficit should occur. (as in Exp. 2). –If the posttarget deficit is event related (related to the presentation of letters), then the posttarget deficit (attention) blink should disappear in the blank condition.

20. Subjects –10; 440 RSVP trials/subject Procedure & Design –440 RSVP trials; –4 blank intervals (0, 90, 180, 270ms), each had 100 trials; among them half of the trials had a probe, and the remaining half did not have a probe. –5 posttarget events (+1, +2, +3, +4, +7) were intermixed in each of the four blank intervals (10 trials each)

21. 40 additional trials –the blank was presented at 450ms or 540 ms (20 trials each; and the probe was presented only in half of the trials; 10 trials each) –The probe was presented either at +1 or +2 serial position (how many events/letters you see after the target)

22. 400 + 40 trials 400 trials –200 trials (a probe was present) 4 blank intervals: 0, 90, 180, 270ms (50 trials each) –200 trials (a probe was absent) 4 blank intervals: 0, 90, 180, 270ms (50 trials each)