Reaction times dependence on luminance spatial noise for a pseudo-isochromatic stimuli

CORMENZANA MÉNDEZ, IÑAKI; O'DONELL, BEATRIZ; MARTÍN, ANDRÉS; SOUZA, GIVAGO S

Belgrado

Conferencia; 37th European Conference on Visual Perception ECVP 2014; 2014

University of Belgrade and the University of Novi Sad

The objective is to analyze the role of amplitude and mean luminance noise for color reaction time -RT- task using pseudoisochromatic stimuli. The stimuli were composed by a Landolt-C surrounded by a background that differed only in chromaticity. Target chromaticity varied along chromatic vectors (0, 90, 180 and 270 deg). Subjects had to find the orientation of the C-Landolt gap while the chromatic vector was decreased. The RT task was performed against luminance noise at three noise mean luminance (13, 19, and 25 cd/m2). The luminance noise modulation was composed by patches with luminance ranging between 7 cd/m2 above and below stimulus mean luminance (constant delta protocol) or by luminance ranging between 70% above and below stimulus mean luminance (constant proportion protocol). The results showed that RT decreased with luminance with constant delta protocol while in the case of constant proportion protocol there is no dependence with luminance within the luminance range analyzed, being longer - ≈100 ms - in the later case. Gomes et al, 2012, showed similar results but measuring color discrimination vector length. On the other hand, the number of wrong answer depends on the protocol, bigger for constant proportion protocol than for constant delta protocol.