ATTENTIONAL CONTROL OF EARLY PERCEPTUAL-LEARNING

The performance of adult humans in simple visual tasks improves dramat ically with practice. This improvement is highly specific to basic att ributes of the trained stimulus, suggesting that the underlying change s occur at low-level processing stages in the brain, where different o rientations and spatial frequencies are handled by separate channels. We asked whether these practice effects are determined solely by activ ity in stimulus-driven mechanisms or whether high-level attentional me chanisms, which are linked to the perceptual task, might control the l earning process. We found that practicing one task did not improve per formance in an alternative task, even though both tasks used exactly t he same visual stimuli but depended on different stimulus attributes ( either orientation of local elements or global shape). Moreover, even when the experiment was designed so that the same responses were assoc iated with the same stimuli (although subjects were instructed to atte nd to the attribute underlying one task), learning did not transfer fr om one task to the other. These results suggest that specific high-lev el attentional mechanisms, controlling changes at early visual process ing levels, are essential in perceptual learning.