1. Attentionally Dependent Bilateral Advantage on Numerosity Judgments Jenny Ewing & Nestor Matthews Department of Psychology, Denison University, Granville OH 43023 USA The Motivating Syllogism Premise 1 - Laterality affects attention. Premise 2 - Attention affects perceptual learning. Prediction - Laterality affects perceptual learning. Operational Definitions: Laterality is a variable that describes the spatial distribution of stimuli. Unilateral stimuli are restricted either entirely to the left hemifield, or entirely to the right hemifield. Bilateral stimuli are distributed across the left and right hemifields. Attention is the selection of a sensory event. Perceptual learning –in vision- is any practice-driven improvement in visual ability. Several previous studies support the premise that laterality affects attention. Specifically, a bilateral attentional advantage has been reported on several attentional tasks. These include motion tracking (Alvarez & Cavanagh, 2005), letter identification (Awh & Pashler, 2000), letter- orientation discrimination in displays that exhibit crowding (Chakravarthi & Cavanagh, 2009), and detecting Gabor targets while ignoring Gabor distractors (Reardon, Kelly & Matthews, 2009). A preliminary study also indicated a bilateral advantage for numerosity judgments (Delvenne et al., 2009). The premise that attention affects perceptual learning is supported by studies showing practice-driven improvements for attended, but not unattended, features of a given training stimulus. Such attentionally specific perceptual learning has been reported for a variety of features: Luminance vs orientation (Shiu & Pashler,1992); local vs global orientation (Ahissar & Hochstein, 1994); direction of motion vs speed of motion (Saffell & Matthews, 2003). Synthesizing those prior findings, here we tested the prediction that laterality affects perceptual learning –with attention as the mediating factor. Building on Delvenne et al. (2009), laterality was investigated while participants judged the numerosity of dot ensembles having a single color, or two colors. The two color condition was designed to reduce similarity-based perceptual grouping, thereby increasing the attentional load and the concomitant bilateral superiority. All participants trained unilaterally for three days. On the fourth day, participants were tested either unilaterally again, or bilaterally for transfer of learning. Measuring transfer was particularly interesting, as the stimuli, task, and spatial positions were identical in our training and test phases -which differed only in the attended laterality (unilateral versus bilateral). Discussion Introduction References Method Stimuli in One Color Condition Results * * * * Ahissar & Hochstein (1993). Attentional control of early perceptual learning. Proceedings of the National Academy of Sciences, 90(12), 5718-5722. Alvarez, G. & Cavanagh, P., (2005). Independent Resources for Attentional Tracking in the Left and Right visual Hemifields. Psychological Science, 16(8), 637-643. Awh, E., & Pashler, H. (2000). Evidence for split attentional foci. Journal of Experimental Psychology: Human perception and performance, 26(2), 834- 846. Chakravarthi & Cavanagh (2009). Bilateral field advantage in visual crowding. Vision Research, 49(13), 1638-1646. Delvenne, J.F., Castronovo, J., Demeyere, N., & Humphreys, G. (2009). Enumerating visual items within and across hemifields. Vision Sciences Society, 63.406, (abstract). Pillow, J., & Rubin, N., (2002). Perceptual Completion across the Vertical Meridian and the Role of Early Visual Cortex. Neuron, 33, 805-813. Reardon, K., Kelly, J., & Matthews, N., (2009). Bilateral Attentional advantage on elementary visual tasks. Vision Research, 49(2009), 691-701. Saffell, T., & Matthews, N. (2003). Task-specific perceptual learning on speed and direction discrimination. Vision Research, 43(12), 1365-1374. Shiu & Pashler (1992). Improvement in line orientation discrimination is retinally local but dependent on cognitive set. Perception & Psychophysics, 52(5), 582-588. Stimuli in Two Color Condition Study 1 Study 2 Participants: 43 Denison University undergraduates/staff IVs: 2 (Laterality) x 4 (Day) x 2 (Color) Laterality: All trained unilaterally on days 1, 2, & 3 Day 4: Half tested unilaterally, half bilaterally Day: 1 - 4 Color: Half saw only 1 color, half saw 2 dot colors DV: Proficiency (d’ / RT) Stimulus shown for 200 milliseconds. Dot diameter: 1.6 cm Although we observed bilateral superiority on the two-color condition in experiment 1, that effect did not replicate on either color condition in experiment 2. Within each of the four (color by laterality) groups in experiment 2, significant learning occurred. The learning transferred completely from the trained to the untrained laterality. This complete transfer contrasts with most previous perceptual learning studies, which typically have shown practiced-based improvements that are specific to the trained conditions. The difference likely reflects the fact that the present stimuli, task, and spatial positions were identical in our training and test phases -which differed only in the attended laterality (unilateral versus bilateral). The complete transfer observed here suggests that the attended laterality was NOT the factor which limited performance. The present study required enumeration by proximity within each quadrant. Current research in our lab is addressing enumeration by (color) similarity across quadrants. Cross-quadrant perceptual grouping has been shown to generate bilateral inferiority in shape-discrimination (Pillow & Rubin, 2002), presumably reflecting time to cross the corpus callosum. A comparable cost for similarity-based enumeration would suggest that proximity and similarity are affected differently by laterality. Participants:28 Denison University undergraduates IVs: 3 (Laterality) x 2 (Color) Laterality: Bilateral vs Unilateral vs Diagonal Color: One dot color versus Two dot colors DV: Proficiency (d’ / RT) Hits: “Different” response when number of dots differed False Alarms: “Different” response when number of dots was the same. Poster Session III Board III - 022 Series of Stimuli and Questions Study 1 Study 2 Learning (day 1-day 4): F(1,42)=189.00, p<.001, pEta^2=.82, power=1 Laterality (one color-Bi vs. Uni): F(1,19)=.09, p=.76, pEta^2=.01, power=.06 Laterality (two color-Bi vs. Uni): F(1,20)=.862, p=.364, pEta^2=.04, power=.143, Laterality: F (2, 48) = 15.753, p <. 001, pEta^2=.396, power=.999 Color: F(1,24)=3.241, p=.054, pEta^2=.119, power=.48 Laterality x Color: F(2,48)=19.106, p,.001, pEta^2=.4438, power=1 2 Color Bi vs. Uni: t(24)=7.561, p<.001 1.Which letter appeared in the center of the screen? 2. Were the numerosities in the cued quadrants the same or different?