Voluntary attention increases the phenomenal length of briefly flashed lines Masin S. C.

1. Voluntary attention increases the phenomenal length of briefly flashed lines Masin S. C. University of Padua

2. The study reported here is about the possible effect of attention on the phenomenal length of briefly flashed lines.

3. The study reported here is about the possible effect of attention on the phenomenal length of briefly flashed lines. A briefly flashed line is, for example, a black line as this:

4. The study reported here is about the possible effect of attention on the phenomenal length of briefly flashed lines. A briefly flashed line is, for example, a black line as this:

5. The study reported here is about the possible effect of attention on the phenomenal length of briefly flashed lines. A briefly flashed line is, for example, a black line as this:

6. There have been many attempts at determining whether attention affects the phenomenal length of briefly presented lines.

7. There have been many attempts at determining whether attention affects the phenomenal length of briefly presented lines. However, although previous studies claim that attention influences phenomenal length, in reality the results of these studies do not allow one to distinguish the effect of attention on phenomenal length from the effect of attention on remembered length.

8. There have been many attempts at determining whether attention affects the phenomenal length of briefly presented lines. However, although previous studies claim that attention influences phenomenal length, in reality the results of these studies do not allow one to distinguish the effect of attention on phenomenal length from the effect of attention on remembered length. The reason for this confusion is the following.

9. For example, PRINZMETAL and WILSON(1997) studied the effect of attention on line length by presenting a fixation cross as this:

10. For example, PRINZMETAL and WILSON(1997) studied the effect of attention on line length by presenting a fixation cross as this:

11. The fixation cross was followed by a stimulus like this:

12. The fixation cross was followed by a stimulus like this:

13. The fixation cross was followed by a stimulus like this: (The duration of the stimulus was about 50 msec)

14. The fixation cross was followed by a stimulus like this: (The duration of the stimulus was about 50 msec) Subjects had the task to detect a letter in this matrix.

15. The fixation cross was followed by a stimulus like this: (The duration of the stimulus was about 50 msec) Subjects had the task to detect a letter in this matrix. This test line was simultaneous with the matrix or appeared 0.5 sec after the matrix.

16. The fixation cross was followed by a stimulus like this: (The duration of the stimulus was about 50 msec) Subjects had the task to detect a letter in this matrix. This test line was simultaneous with the matrix or appeared 0.5 sec after the matrix. Thus the test line received more attention when it appeared after the matrix.

17. Several seconds after the test line and the matrix had disappeared, subjects varied the length of a comparison line such as this…

18. Several seconds after the test line and the matrix had disappeared, subjects varied the length of a comparison line such as this…

19. Several seconds after the test line and the matrix had disappeared, subjects varied the length of a comparison line such as this… …to make it equal to the length of the test line.

20. Several seconds after the test line and the matrix had disappeared, subjects varied the length of a comparison line such as this… …to make it equal to the length of the test line.

21. Several seconds after the test line and the matrix had disappeared, subjects varied the length of a comparison line such as this… …to make it equal to the length of the test line. Clearly, the comparison line was compared with the memory of the test line, not with the phenomenal length of the test line, because the comparison occurred…

22. Several seconds after the test line and the matrix had disappeared, subjects varied the length of a comparison line such as this… …to make it equal to the length of the test line. Clearly, the comparison line was compared with the memory of the test line, not with the phenomenal length of the test line, because the comparison occurred…

23. Several seconds after the test line and the matrix had disappeared, subjects varied the length of a comparison line such as this… …to make it equal to the length of the test line. Clearly, the comparison line was compared with the memory of the test line, not with the phenomenal length of the test line, because the comparison occurred…

24. PRINZMETAL and WILSON(1997) found that the adjusted comparison line was longer when the test line received more attention.

25. PRINZMETAL and WILSON(1997) found that the adjusted comparison line was longer when the test line received more attention. However, as we have just seen, this effect of attention could well have been a memory effect rather than a phenomenal effect.

26. PRINZMETAL and WILSON(1997) found that the adjusted comparison line was longer when the test line received more attention. However, as we have just seen, this effect of attention could well have been a memory effect rather than a phenomenal effect. To resolve this issue, the following study was carried out.

27. In the following experiment, a white fixation cross was presented on each trial.

28. In the following experiment, a white fixation cross was presented on each trial.

29. The subjects were instructed to direct their attention on the side of the cross indicated by the blackening of one arm.

30. The subjects were instructed to direct their attention on the side of the cross indicated by the blackening of one arm. For example…

31. The subjects were instructed to direct their attention on the side of the cross indicated by the blackening of one arm. For example… on the left

32. The subjects were instructed to direct their attention on the side of the cross indicated by the blackening of one arm. For example… on the right

33. The subjects were instructed to direct their attention on the side of the cross indicated by the blackening of one arm. For example… on the top

34. The subjects were instructed to direct their attention on the side of the cross indicated by the blackening of one arm. For example… at the bottom

35. The test line and the comparison line had a width of 1 pixel and a length of 50 mm. They were presented simultaneously for 50 msec

36. The test line and the comparison line had a width of 1 pixel and a length of 50 mm. They were presented simultaneously for 50 msec vertically

37. The test line and the comparison line had a width of 1 pixel and a length of 50 mm. They were presented simultaneously for 50 msec vertically or horizontally.

38. The test line and the comparison line were presented few milliseconds before or after one arm of the cross turned black.

39. For example the test line and the comparison line were presented like this…

40. For example the test line and the comparison line were presented like this…

41. For example the test line and the comparison line were presented like this…

42. For example the test line and the comparison line were presented like this…

43. For example the test line and the comparison line were presented like this… By definition, the test line was the line indicated by the black arm of the cross.

44. For example the test line and the comparison line were presented like this… By definition, the test line was the line indicated by the black arm of the cross. In the case just shown, subjects had to report whether the test line (located on the left) was longer or shorter than the comparison line (located on the right).

46. Let this line represent the time axis.

47. This arrow represents the moment when one arm of the fixation cross turnes black (that is, the moment when the cue occurs).

48. This solid line represents the duration of the test line (50 msec).

49. This arrow represents the moment when attention is deployed.

50. This arrow represent the moment when attention is deployed. CARLSON, HOGENDOORN, and VERSTRATEN (2006) have recently shown that voluntary attention is deployed about 240 msec from when a cue occurs.