Ventral Stream has the Final Say in the (Mis)Localization of the Flash Jump Effect.

Poster Session E - Monday, April 15, 2024, 2:30 – 4:30 pm EDT, Sheraton Hall ABC

Heather Jordan¹ (jordanh@uoguelph.ca), Martina Malito¹, Mazyar Fallah¹; ¹University of Guelph

A flashed colored bar is misperceived further along the trajectory of motion than its actual location (Flash Jump Effect: FJE), reflecting misintegration of color and extrapolated motion. Manual responses to the perceived location of the color flash are modulated by the strength of ventral stream feature representations (Saini et al, 2021; Sundberg et al, 2005). Can FJE be observed using a saccade response that relies on metrically-accurate dorsal stream representations? We measured FJE when participants made a saccade or manually moved a cursor to the remembered location of the colored flash at the end of each trial. Similar FJEs were observed for both Manual (1.26 dva) and Saccadic (1.53 dva; both p<.001) responses. FJE is observed even when programming the response to a flash in eye-centered coordinates. Given sufficient time, perceived location from the ventral stream may update dorsal-stream representations of the actual flash location. In a second experiment, participants immediately made a saccade to the colored flash, rather than delaying until the end of the trial. We expected to observe the FJE for ventral stream manual response but lose it for the dorsal-stream saccadic response. We observed significant FJE for Manual (1.58 dva) but also Saccadic (2.61 dva) responses (both p<.001). In addition, the saccadic FJE was significantly larger for immediate compared to delayed responses (p = .003) but not the manual (p = .105) effect. Therefore, the dorsal stream is more vulnerable to temporal-spatial mislocalizations, but with time is updated by the ventral stream to reduce the FJE.

Topic Area: PERCEPTION & ACTION: Vision