Not All Probabilities Are Equivalent: Evidence From Orientation Versus Spatial Probability Learning
Frequently targets are detected faster, probable locations searched earlier, and likely orientations estimated more precisely. Are these all consequences of a single, domain-general “attentional” effect? To examine this issue, participants were shown brief instances of spatial gratings, and were tasked to draw their location and orientation. Unknown to participants, either the location or orientation probability of these gratings were manipulated. While orientation probability affected the precision of orientation reports, spatial probability did not. Further, utilising lowered stimulus contrast (via a staircase procedure) and a combination of behavioral precision and confidence self-report, we clustered trials with perceived stimuli from trials where the target was not detected: Spatial probability only modulated the likelihood of stimulus detection, but not did not modulate perceptual precision. Even when no physical attentional cues are present, acquired probabilistic information on space versus orientation leads to separable ‘attention-like’ effects on behaviour. We discuss how this could be linked to distinct underlying neural mechanisms.