Spatial attention and expectancy for colour, category and location: further evidence against the spotlight model

Efficiency of Selective Attention: Selection by Colour and Location Compared

Although we can selectively attend to colour, preknowledge of the location of a target has been shown to facilitate visual selection more than preknowledge of the target colour. Here the effects of peripheral flash cues and central colour cues were compared in three experiments. A novel colour-cuing procedure was used in which the target location was designated in advance by colour. Since variations in stimulus eccentricity and density similarly affected performance in both conditions, the colour cues presumably also made it possible to direct attention quickly to the target location. Thus, the colour cues in this study were analogous to symbolic location cues, such as central digits. Moreover, even though peripheral colour information was provided in experiments 1 and 2 only 84 ms before stimulus array, ie at the same time as the onset cue was flashed on, the effect of colour cues was comparable to that of peripheral flashes. This is a surprising finding given previous data on the time to interpret symbolic location cues and to allocate attention to the target location.

Effects of task factors on selection by color in the rapid serial visual presentation (RSVP) task

In five experiments, we examined task factors influencing selection by color in a rapid serial visual presentation (RSVP) task. Participants were required to respond to the presence or case of a target letter presented within an RSVP sequence, and they were cued as to the color in which that target was most likely to occur. The first two experiments explored the effect of task difficulty. It was found that a change from the discrimination of upper- versus lowercase targets to the detection of an exact shape had no influence on the color-cuing effect. In contrast, increasing letter set discriminability and decreasing color discriminability reduced the color-cuing effect considerably, although they did not eliminate it. In the third and fourth experiments, the frequency of valid trials was reduced, removing the incentive to use the color information. Again, a small benefit remained, indicating partially automatic and strategic color-processing components. Finally, the fifth experiment showed that an increase in perceptual load had no influence on the color-cuing effect. Together, these five experiments provide further evidence of the robustness of direct selection by color.

Direct selection by color for visual encoding

In two experiments, we used rapid serial visual presentation tasks to examine the usefulness of color for the direct selection of visual information for perceptual encoding. The participants' task was to make a discrimination as to whether a target letter within a rapid sequence appeared in its upper- or lowercase version, and an advance cue indicated the color in which the target letter was most likely to occur. To maximize the usefulness of the cued color, in validly cued trials, we used sequences in which the target was the only item appearing in the cued color. In both experiments, accuracy was highest for validly cued trials. A cost-benefit analysis revealed a facilitory effect of valid cues and an inhibitory effect of invalid ones. These results support the idea that color cuing allows the direct selection of objects for further perceptual processing.

Spatial orienting controlled without awareness: a semantically based implicit learning effect

Three experiments tested whether spatial attention can be influenced by a predictive relation between incidental information and the location of target events. Subjects performed a simple dot detection task; 600 msec prior to each target a word was presented briefly 5 degrees to the left or right of fixation. There was a predictive relationship between the semantic category (living or non-living) of the words and target location. However, subjects were instructed to ignore the words, and a post-experiment questionnaire confirmed that they remained unaware of the word-target relationship. In all three experiments, given some practice on the task, response times were faster when target appeared at likely ( p = 0.8 ), compared to unlikely ( p = 0.2 ) locations, in relation to lateral word category. Experiments 2 and 3 confirmed that this effect was driven by semantic encoding of the irrelevant words, and not by repetition of individual stimuli. Theoretical implications of this finding are discussed.

Color-based inhibition of return

The inhibition of return of visual attention based on stimulus color was examined in three experiments. In the first experiment, a discrete trial paradigm showed that subjects were slower to detect a color patch if the color matched that of a patch presented earlier in the same location. Experiment 2 showed that the inhibition only occurs if a neutral, nontarget distractor color is presented between presentation of the initial color cue and the subsequent target patch--explaining the previous failures to detect the phenomenon. Experiment 3 extended the results to a different combination of colors. Taken together, the results have important implications for the processing of stimulus attributes such as spatial location and color, and for the conditions necessary for producing inhibition of return.

Temporal properties of colour and shape priming: evidence of multiple components of attention

It has been shown in several studies that the selection of letters or numerals from an array can occur efficiently if criteria such as location, colour, shape, or size are used. It is also known that there are at least two components of spatial attention, the transient exogenous and the sustained endogenous. An interesting question is whether it is possible to elicit similar components when colour or shape information is used as a selection criterion. Experiments are reported the aim of which was to try to produce colour or shape precue effects on location and colour/shape discrimination accuracy, and to determine the minimum latency of these effects by sampling numerous cue lead times from 0 ms to 1000 ms. The results showed that, although accuracy did not increase monotonically with increased cue lead time, there were two transient peaks of performance at cue lead times of 0-200 ms, culminating at 30-50 ms and at 160-200 ms. It is suggested that the first component reflects nonspecific exogenous activation, triggered by the onset of a cue; the second component, in turn, may reflect feature-specific endogenous activation related to selection by colour or shape.