Contrast coding and magno/parvo segregation revealed in reaction time studies

Abstract

Reaction times (RTs) are obtained for a wide range of contrasts of vertical sinusoidal gratings. The data are plotted as a function of the reciprocal of contrast. In some conditions, a single linear function accounts for the data. In others a clear bi-linear function is obtained. The low and high contrast regions of the function are interpreted as representing magno and parvo activity, respectively. RT-based supra-threshold sensitivity functions are obtained for different luminances, stimulus durations and eccentricities and these are compared with conventional threshold-based sensitivities to establish the extent to which RTs and contrast sensitivity are constrained by the same sensory processes.

The effect of target contrast on the attentional blink

“…Pooled across the relevant experiments, 10 the correlation (r) between T1 performance and T1-distractor relative contrast was .84 ( p Ͻ .001). These results either replicate or are consistent with those in the psychophysical literature (Ejima & Otani, 1987;Gish et al, 1986;Lupp et al, 1976;Murray & Plainis, 2003;Plainis & Murray, 2000;Tiipana, Paramei, & Alshuth, 2001). …”

“…Detection and identification performance is a monotonically increasing function of contrast (Graham, 1989). Reaction time to a spatial pattern decreases as its contrast increases (Ejima & Ohtani, 1987;Gish, Shulman, Sheehy, & Leibowitz, 1986;Lupp, Hauske, & Wolf, 1976;Murray & Plainis, 2003;Plainis & Murray, 2000;Thompson & Drasdo, 1989), implying that increases in contrast allow faster information accumulation and/or improve processing efficiency. The neurophysiological evidence accords well with the psychophysical data.…”

Evidence for an attentional component in saccadic inhibition of return

“…The decrease of reaction times with increasing stimulus contrast is much steeper for contrasts below 10% than it is for larger contrasts (e.g. Murray and Plainis 2003). Therefore, we expect larger beneWts of attention in our experiment, because we used a contrast of 7.1% for our low-contrast target.…”

Shape discrimination by wasps (Paravespula germanica) at the food source: generalization among various types of contrast

“…In the honeybee, several experiments (reviewed by Lehrer 1993b) revealed that colour, shape and motion are processed in parallel and independently, a conclusion already drawn for human vision from psychophysical tests (Livingstone and Hubel 1987;Shiller and Logothetis1990;Burr et al 1994;Murray and Plainis 2003) (but see Gegenfurtner and Hawken 1996;Willis and Anderson 2002).…”