Maryam Vaziri Pashkam

Unintended imitation affects success in a competitive game

Significance People have a strong tendency to imitate each other in social interaction. Here, we show that imitation is also persistent in a competitive context. In our experiments, participants performed a two-player arcade game in which they could win money when they quickly hit targets on a touchscreen before their opponent. We demonstrate that reaction times and movements of players were highly synchronized and the financial rewards could not withhold players from imitating slow opponents. Imitation persisted, even when there was no need to follow the opponent’s actions. Imitation typically occurs in social contexts where people interact and have common goals. Here, we show that people are also highly susceptible to imitate each other in a competitive context. Pairs of players performed a competitive and fast-reaching task (a variant of the arcade whac-a-mole game) in which money could be earned if players hit brief-appearing visual targets on a large touchscreen before their opponents. In three separate experiments, we demonstrate that reaction times and movements were highly correlated within pairs of players. Players affected their success by imitating each other, and imitation depended on the visibility of the opponent’s behavior. Imitation persisted, despite the competitive and demanding nature of the game, even if this resulted in lower scores and payoffs and even when there was no need to counteract the opponent’s actions.

Spatiotopic priming in visual search

Visual search is faster if the target appears in the same location on consecutive trials than if it appears in different locations. In this study, we investigated how this location priming is affected by eye movements. Subjects were asked to report the orientation of a T-shaped target embedded among L-shaped distracters in a 2 x 4 array. Trials were organized in pairs and subjects had to perform the task while fixating at a red dot. In the first trial of each pair the fixation point was placed on the left side of the screen and on the second trial it was moved to the right side of the screen. Reaction time of the subjects was analyzed to determine if the location priming in visual search follows a retinotopic reference frame or a spatiotopic one. Results showed a non-specific effect of eye movement direction on the reaction time profile: regardless of the location of the target in the first trial, reaction times significantly decreased along the direction of the saccade (p<0.05). To factor out this general effect each location was compared to the vertically aligned control (previously non-target) location having the same horizontal position. Subjects were significantly faster (p<0.05) in finding a target when it was presented in the same spatiotopic location than in the control location with similar eccentricity. There was no significant difference between the reaction time of the subjects for the retinotopic location compared to control (p=0.1). These results suggest that the visual attention maintains a spatiotopic representation for the attended objectʼs location across eye movements.

Effect of speed overestimation on manual hitting at low luminance

References 1. Vaziri-Pashkam, M., & Cavanagh, P. (2008). Apparent speed increases at low luminance. Journal of Vision, 8(16):9,1-12. 2.Hammett ST, Champion RA, Thompson PG, Morland AB. (2007) Perceptual distortions of speed at low luminance: evidence inconsistent with a Bayesian account of speed encoding. Vision research 47(4), 564-8. 3. Goodale, M. A., & Milner, A. D. (1992). Separate visual pathways for perception and action. Trends Neurosci, 15(1), 20-25. Motor task: Manual Hitting