Academic journal article Canadian Psychology

Attention Based Visual Processes

Academic journal article Canadian Psychology

Attention Based Visual Processes

Article excerpt

Attention is often compared to a spotlight or focus of enhanced processing. We have found that this gain comes with certain unexpected costs. Specifically, judgements of positions of stimuli surrounding an attended event are distorted, repelled away from the attentional focus. But there is more to attention than just selection. Our work shows that it is better characterized as an image which keeps track of attended objects. We find that the resolution or grain of attention -- the finest packing of targets which still allows an individual item to be identified and tracked -- is much coarser than the smallest visual feature which can be resolved.

Moreover, the mere act of tracking an object with attention appears to create impressions of motion. In this sense, attentive tracking is like a pursuit system that involves attention rather than eye movements. Attention - based motion has a limited capacity (Pylyshyn & Storm, 1988) and does not require low - level motion signals in order to keep track of targets. For example, observers can accurately follow equiluminous colour targets with attention even when low - level mechanisms grossly underestimate their apparent velocity. Observations on superimposed luminance and color gratings (Cavanagh, 1992) show that attention - based motion operates independently of low - level motion. Wertheimer (1912) was the first to propose an attention - based motion process (for apparent motion) when he considered the possibility "that the passing across of attention is the phenomenon of motion" (p. 1080). Wertheimer (1912) also reported attentive tracking of ambiguous, counter - phasing, radial spokes which could be seen to rotate in either direction, depending on the "set and posture of attention" (p. 1069). This early work has been replicated recently (Ramachandran & Anstis, 1983; Culham & Cavanagh, 1994a).

One might argue that an attention - based, feature tracking process is not a motion process. In the extreme example of the minute hand of a watch, "motion" is inferred, not sensed. Indeed, attentive tracking may be inherently position based. However, our evidence shows that tracking supports a true motion process. It exhibits effects of fatigue with properties unlike those for low - level mechanisms, and it demonstrates predictive behaviour that goes well beyond simple position analysis. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.