Abstract
Motion aftereffect (MAE) duration is longer for a selectively attended plaid component than for the non-attended component. We have previously shown that this holds whether adaptation is to either: 1) a homogenous plaid made of two first-order gratings, or two second-order gratings, or 2) a heterogeneous plaid made of a mixture of first-order and second-order gratings. Here, the effects of selective attention during adaptation on MAE duration were investigated further with a dynamic test stimulus oriented either like the attended component, the unattended component, or perpendicular to the coherent motion direction. The plaids were composed of two spatially superimposed, but temporally alternating square-wave or sine-wave gratings differing by 140 degrees in motion direction. Results replicate previous findings and further suggest that MAE duration is longer when attending equally to both components than when attending to only one component when test orientation is perpendicular to the coherent motion direction. In a second experiment, MAE was measured for 20 and 40 sec adaptation times. First order: MAE duration was much shorter when attention was alternated between 1st and 2nd order components for 40 sec than when restricted to the 1st order component for 20 sec (same overall attention times). Thus attention operates both via facilitation and suppression. Second order: A similar but reduced effect was present for one observer, but not for the other. The longer MAE in experiment 1, produced when attention was directed to only one component, as opposed to when alternating between the two components, was thus not due to the longer attention time, but to the presence of attentive suppression.
Supported by NSERC and FCAR (MvG).