What methods did we employ in this experiment?

On each trial, a central target arrow was presented at the middle of the experiment frame and your task was to quickly determine whether it pointed to the left, <, or to the right, >.

There are two independent variables. The first is whether the flanking arrows point in the same direction as or in a different direction than the target arrow. The second independent variable is the distance between the flanking arrows and the target arrow (close or far). The dependent variable was the time between the appearance of the stimulus and your response. Trials where you reported the target direction incorrectly were repeated at a random trial later in the experiment.

What do we predict participants will do? Why?

The flanking arrows should affect performance. When the flanking arrows are close to the target arrow, performance is faster when the flanking arrows point in the same direction as the target and slower when the flanking arrows point in the opposite direction. These effects are distance-dependent, and when the flanking arrows are far from the target arrow, it does not matter much whether the flanking arrow directions are the same as or different than the target.

You will use your data to run a Two-way ANOVA (Analysis of Variance) to explore the properties of the flanker effect. This analysis allows you to simultaneously run three related hypothesis tests. The first test explores a main effect for the congruency of the pointing direction of the target and flanking arrows (same or different). The null hypothesis is that the mean reaction times are the same:

H0: same = different,

and the alternative hypothesis is that the mean reaction times are different:

Ha: same different.

The second hypothesis test explores whether mean reaction time varies with the location of the flankers relative to the target arrow. The null hypothesis is that the mean reaction times are the same:

H0: close = far,

with the alternative hypothesis being that the mean reaction times are different:

Ha: close far.

Finally, you can test for an interaction of the main effects. This test investigates whether there is a difference in the differences of means. For example, the effect of arrow direction might be stronger when the flankers are close to the target and weaker when the flankers are far from the target. The null hypothesis is that the difference of mean reaction times for the two close conditions is equal to the difference of reaction times for the two far conditions:

H0: same,close - different,close = same,far - different,far,

with the alternative hypothesis being that the differences are not equal:

Ha: same,close - different,close same,far - different,far,

For all the tests we will use = 0.05.

Mean RT for center and flanking arrows being Same, and the flankers being Close:

(The difference between your answer and the correct value must be less than 0.01.)

Mean RT for center and flanking arrows being Same, and the flankers being Far:

(The difference between your answer and the correct value must be less than 0.01.)

Mean RT for center and flanking arrows being Different, and the flankers being Close:

(The difference between your answer and the correct value must be less than 0.01.)

Mean RT for center and flanking arrows being Different, and the flankers being Far:

(The difference between your answer and the correct value must be less than 0.01.)

F-ratio for relative direction of center and flanking arrows (rows):

(The difference between your answer and the correct value must be less than 0.01.)

p-value for relative direction of center and flanking arrows (rows):

(The difference between your answer and the correct value must be less than 0.001.)

Do you reject the null hypothesis for relative direction of center and flanking arrows?:

F-ratio for flanker location (columns):

(The difference between your answer and the correct value must be less than 0.01.)

p-value for flanker location (columns):

(The difference between your answer and the correct value must be less than 0.001.)

Do you reject the null hypothesis for flanker location?:

F-ratio for the interaction:

(The difference between your answer and the correct value must be less than 0.01.)

p-value for the interaction:

(The difference between your answer and the correct value must be less than 0.001.)

Do you reject the null hypothesis for the interaction?:

Trial- Center > direction-Flank > direction- Center&Flank> Dire- Flank > location- Time (MS)

1 Left Left Same Close 849

2 Right Right Same Close 892

3 Left Left Same Close 1674

4 Left Left Same Far 1153

5 Left Left Same Close 878

6 Right Right Same Close 875

7 Right Right Same Close 885

8 Left Left Same Far 885

9 Right Right Same Far 738

10 Left Left Same Far 802

11 Right Right Same Far 1037

12 Right Left Different Close 1274

13 Right Left Different Close 1043

14 Left Right Different Far 1847

15 Left Right Different Far 962

16 Right Right Same Far 1156

17 Left Right Different Close 1062

18 Right Left Different Far 1041

19 Right Left Different Far 849

20 Left Left Same Close 841

21 Left Left Same Close 1175

22 Right Right Same Close 1111

23 Right Left Different Close 1423

24 Left Right Different Close 1222

25 Left Right Different Far 1063

26 Right Right Same Far 737

27 Right Right Same Far 1036

28 Right Right Same Close 895

29 Left Left Same Far 822

30 Left Left Same Close 1302

31 Left Right Different Close 1706

32 Left Right Different Far 916

33 Left Right Different Far 919

34 Left Right Different Far 817

35 Right Right Same Close 1198

36 Right Right Same Close 865

37 Left Left Same Far 762

38 Right Right Same Close 901

39 Right Left Different Far 1248

40 Left Left Same Far 840

41 Right Right Same Far 790

42 Right Right Same Far 873

43 Right Left Different Close 1083

44 Left Right Different Close 1646

45 Right Left Different Close 1433

46 Right Left Different Far 851

47 Left Right Different Close 1451

48 Right Left Different Close 1569

49 Left Right Different Far 1345

50 Left Left Same Close 971

51 Left Right Different Close 1109

52 Right Right Same Far 845

53 Left Right Different Close 2080

54 Right Left Different Close 1527

55 Left Right Different Far 1210

56 Left Right Different Far 890

57 Right Left Different Far 790

58 Left Right Different Far 949

59 Right Left Different Far 1010

60 Left Left Same Close 877

61 Left Left Same Close 768

62 Left Right Different Close 1084

63 Right Right Same Close 897

64 Right Left Different Far 992

65 Left Left Same Far 746

66 Right Left Different Close 1353

67 Right Left Different Far 1001

68 Left Left Same Far 981

69 Right Left Different Close 1297

70 Left Left Same Far 879

71 Right Left Different Far 936

72 Left Right Different Close 1318

73 Right Left Different Close 1225

74 Left Right Different Close 1374

75 Left Left Same Far 919

76 Right Right Same Far 821

77 Right Right Same Close 793

78 Right Right Same Far 852

79 Right Left Different Far 791

80 Left Left Same Close 934