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Judging Peripheral Change: Attentional and Stimulus-Driven Effects Jenna Kelly & Nestor Matthews Department of Psychology, Denison University, Granville OH 43023 USA Introduction Previous research has revealed performance advantages for stimuli presented across (bilateral) rather than within (unilateral) the left and right hemifields on a variety of spatial attention tasks, including alphanumeric symbol identification (Awh & Pashler, 2000), conjunction and shape identification (Kraft et al. , 2005), multiple object tracking (Alvarez & Cavanagh, 2005), Gabor detection and orientation discrimination (Reardon et al. , 2009), and visual crowding (Chakravarthi & Cavanagh, 2009). Here, we probed for a similar advantage in a temporal attention task. Whether temporal tasks should exhibit the same bilateral advantage is non-obvious because temporal and spatial attention have different properties (Aghdaee & Cavanagh , 2007). Some of these hemifield effects emerge only in the presence of distracters. It may be important whether the distracters add difficulty in a task-relevant way; task-irrelevant difficulty may not compete for attentional resources enough to generate a bilateral advantage. Evidence from Taya et al. (2009) and Reardon et al. (2009) supports the importance of task-relevance in driving the observed hemifield effects. Here, we look for hemifield effects in a temporal attention task alone and in comparison to a spatial attention task, with a particular interest in the distinction between the properties of temporal and spatial attention and the impact of task-relevant difficulty. References Aghdaee, S. M. , & Cavanagh, P. (2007). Temporal limits of long-range phase discrimination across the visual field. Vision Research 47, 2156 -2163. Alvarez, G. A. , & Cavanagh, P. (2005). Independent resources for attentional tracking in the left and right visual hemifields. Psychological Science 16, 637 -643. Awh, E. , & Pashler, H. (2000). Evidence for split attentional foci. Journal of Experimental Psychology: Human Perception and Performance 26, 834 -846. Chakravarthi, R. , & Cavanagh, P. (2009). Bilateral field advantage in visual crowding. Vision Research 49, 1638 -1646. Kraft, A. , et al. (2005). Interactions between task difficulty and hemispheric distribution of attended locations: implications for the splitting attention debate. Cognitive Brain Research 24, 19 -32. Reardon, K. M. , Kelly, J. G. , & Matthews, N. (2009). Bilateral attentional advantage on elementary visual tasks. Vision Research 49, 692 -702. Taya, S. , Adams, W. J. , Graf, E. W. , & Lavie, N. (2009). The fate of task-irrelevant visual motion: Perceptual load versus feature-based attention. Journal of Vision 9, 1 -10. Westheimer, G. (2003). Meridional anisotropy in visual processing: Implications for the neural site of the oblique effect. Vision Research 43, 2281 -2289. Experiment 1: Temporal Asynchrony Alone Method Experiment 2: Spatial vs. Temporal Stimuli Attentional Cue m Peripheral Response Prompts Letter Response Prompt Peripheral Response Prompt Attentional Cue Experimental Details Which Letter? Stimuli Letter Response Prompt Target Stripe Size? same = s different = d Training Paradigm Target Timing? same = s different = d m Which Letter? Target Timing? same = s different = d m Discriminanda: high (89. 76% Michelson) contrast, 14. 55 deg diagonally from fixation, max/min luminances = 108. 00, 5. 83 cd/m 2 • Participants: 23 Denison University undergraduates • IVs: 3 (Laterality) x 3 (Distracter) • Laterality = Bilateral , Unilateral, Diagonal • Distracter = Absent, Static, Dynamic * • Participants: 19 Denison University undergraduates • IVs: 3 (Laterality) x 2 (Task) x 2 (Day) • Task = Spatial vs. Temporal • Day=2 (task blocked) vs. 3 (task unknown until prompt) Results Experiment 1: Temporal Asynchrony Alone Experiment 2: Comparing Tasks and Days Experiment 2: Day 3 Laterality x distracter interaction effect: F (4, 88) = 2. 520, p = 0. 047, partial η 2 = 0. 103 Laterality effect, distracters absent: F (2, 44) = 3. 457, p = 0. 040, partial η 2 = 0. 136 Distracter main effect: F (1. 344, 29. 566) = 13. 146, p < 0. 0005, partial η 2 = 0. 374 Laterality main effect : F (2, 36) = 17. 304, p < 0. 0005, partial η 2 = 0. 490 Day main effect: F (1, 18) = 38. 032, p < 0. 0005, partial η 2 = 0. 679 Laterality x Task x Day: F (2, 36) = 0. 473, p = 0. 627, partial η 2 = 0. 026 F (2, 36) = 12. 861, p < 0. 0005, partial η 2 = 0. 417 http: //denison. edu/~matthewsn/spacetimeattentionvss 2010. html Poster # 26. 314 Abstract # 413 Discussion When distracters were absent, proficiency (d’/RT) was significantly lower in the diagonal condition than in either of the bilateral or unilateral conditions, which were statistically indistinguishable. This oblique effect was eliminated in the presence of either distracter type but maintained with the addition of the concurrent spatial task. The lower proficiency in the diagonal condition—in which targets were in opposite hemifields— prevents the attribution of this effect to laterality. This pattern differs from that observed in previous spatial attention tasks, suggesting that the properties of spatial and temporal attention may differ. We seem to have found an oblique effect, like that of Westheimer (2003), for a task in which orientation is determined by the entire configuration rather than by any of the components, and we have extended this sort of oblique effect to a timing comparison. It is possible that the effect observed here is actually one of distance; while targets are the same distance from fixation across laterality conditions, the distance across which the comparison is made is √(2) times longer on diagonal trials than on bilateral or unilateral trials. This deserves further consideration but may be tentatively refuted by the results of Kraft et al. (2005), which suggest that target-target distance may affect performance within but not between hemifields. Our apparent oblique effect might also result from the collinear relationship between the two targets and fixation on diagonal trials, which is not present on either bilateral or unilateral trials. This cannot be refuted by our data but would predict a counterintuitive effect of shifting the fixation point to a location horizontally or vertically intermediate to a pair of targets: if collinearity produces a performance deficit, then pairs of targets closer to fixation will be associated with lower performance than more distant targets that are not collinear with fixation. Such a finding would be surprising. Regardless of the reason for the lower performance on diagonal trials in this task, it is important to note that the effect generalizes across spatial and temporal attention tasks, which suggests that the two types of attention may share some properties. Even though the distracters and multitasking each made the task more difficult, the cardinal advantage was eliminated only by distracters. Thus, it is not task difficulty per se that drives the effect. It may be that the distracters, but not the concurrent spatial frequency judgment task, provides task-relevant difficulty that generates the observed oblique effect. The importance of task-relevant difficulty has also been shown for spatial attention-dependent tasks (e. g. Kraft et al. , 2005).