We show that cast shadows can have a significant influence on the speed of visual search. In particular, we find that search based on the shape of a region is affected when the region is darker than the background and corresponds to a shadow formed by lighting from above. Results support the proposal that an early-level system rapidly identifies regions as shadows and then discounts them, making their shapes more difficult to access. Several constraints used by this system are mapped (...) out, including constraints on the luminance and texture of the shadow region, and on the nature of the item casting the shadow. Among other things, this system is found to distinguish between line elements (items containing only edges) and surface elements (items containing visible surfaces), with only the latter deemed capable of casting a shadow. (shrink)

Cognitive impenetrability is really two assertions: (1) perception and cognition have access to different knowledge bases; and (2) perception does not use cognitive-style processes. The first leads to the unusual corollary that cognition is itself cognitively impenetrable. The second fails when it is seen to be the claim that reasoning is available only in conscious processing.

The authors review how attention helps track and process dynamic events, selecting and integrating information across time and space to produce a continuing identity for a moving, changing target. Rather than a fixed ‘spotlight’ that helps identify a static target, attention needs a mobile window or ‘pointer’ to track a moving target, picking up pieces of evidence along the way to determine not just what the target is, but what it is doing. Behavioural studies show that this dynamic version of (...) attention is model-based, using familiar trajectories to help identify a target and to guide encoding of continuing input from its path. Attention has very coarse temporal resolution for both static and moving targets. However, when the focus of selection is on the move, a given location on a moving target’s path can be selected for extremely brief instants, as little as 50 ms, compared to the typical ‘dwell time’ or minimum duration of attention selection at a fixed location, of 200 ms or more. To determine the path of a moving object, attention must accurately process and sort the onsets and offsets in order to match an offset to the subsequent onset. This aspect of dynamic attention has been called the ‘when’ pathway and patient studies show that it is a qualitatively different system from spatial attention, being completely based in the right parietal lobe for events in both hemifields. Finally, like the salience map of spatial attention, temporal attention may have its own map that guides allocation to upcoming, current, and recent moments to select information at the appropriate time, changing the experience of time as it does so. (shrink)

Attention can be oriented in space covertly without the need of eye movements. We used multivariate pattern classification analyses (MVPA) to investigate whether the time course of the deployment of covert spatial attention leading up to the observer’s perceptual decision can be decoded from both EEG alpha power and raw activity traces. Decoding attention from these signals can help determine whether raw EEG signals and alpha power reflect the same or distinct features of attentional selection. Using a classical cueing task, (...) we showed that the orientation of covert spatial attention can be decoded by both signals. However, raw activity and alpha power may reflect different features of spatial attention, with alpha power more associated with the orientation of covert attention in space and raw activity with the influence of attention on perceptual processes. (shrink)