The effects of cue size manipulations on target processing efficiency

The spotlight model likens visual attention to a spotlight beam which "illuminates" specific positions of a visual display, thus enabling stimuli falling within the attended area to receive enhanced levels of processing. The zoom-lens model suggests that the size of the attentional spotlight is flexible to change in accordance with task demands. Directing attention to a small area of the visual display narrows the size of the attentional spotlight, thus increasing the concentration of attentional resources within the attended area. As a result, this should increase the processing efficiency of stimuli falling within the attended area. Empirical investigations of the zoom-lens model typically involve measuring target processing efficiency as a function of the size of a cued attended area within which the target is presented. Findings of an inverse relationship between size of a cued attended area and subsequent target processing efficiency has also been referred to as an attentional cue-size effect. A large proportion of the evidence supporting an attentional cue-size effect has come from studies that used single-element detection tasks which measure detection latencies of a target that is presented alone in the absence of surrounding noise. However, most of these studies did not have a control cue condition to first establish if their spatial cueing paradigms were truly effective in drawing on attentional processes. Without first establishing if their spatial cue was effective in serving attentional benefits to task performance, subsequent findings of a cue-size effect on task performance cannot be attributed to the attentional spotlight having changed in size as a result of the experimental cue size manipulations. The work presented in this thesis investigated the idea of an attentional cue-size effect by conducting a series of single-element detection tasks similar to those used by previous investigations of the cue-size effect. A control condition was implemented throughout all the experiments in order to establish if the spatial cue used in these tasks was truly effective in drawing on the attentional spotlight and serving attentional benefits to task performance. The overall pattern of results does not support the idea of an attentional cue-size effect. Rather, cue-size effects found on the error rates (e.g., anticipatory response and false alarm rates) as well as on target response latencies seem more suitably explained by the idea that the participant's response criterion was lowered in the small cue condition, possibly as a result of the small cue sharing size similarities with the target relative to a larger cue which was also presented within the same context of trials. The present thesis also discusses serious confounds that may arise as a result of using reaction-time tasks to tap attentional and perceptual phenomena. As revealed by the overall latency and error trends throughout the experiments presented in this thesis, extraneous mental processes not relevant to the experimental manipulations, such as response inhibitory and target-arrival anticipatory processes as well as stimulus discrimination processes, are likely to also be manifested in the overall response latency trend, thereby confounding any true attentional effects that may potentially result from the experimental manipulations.