Control of attention by a peripheral visual cue depends on whether the target is difficult to discriminate

Abstract

The influence of a peripheral cue represented by a gray ring on responsivity to a subsequent target varies. When a vertical line inside a ring was a go target and a white small ring inside a ring was a no-go target, reaction time was shorter at the same location relative to a different location. However, no reaction time difference between the two locations occurred when a white cross inside the ring, instead of the white vertical line inside the ring, was the go target. We investigated whether this last finding was due to a forward masking influence of the cue, a requirement of low attention for the discrimination or a lack of attention mobilization by the cue. In Experiment 1, the intensity of the cue was reduced in an attempt to reduce forward masking. In Experiment 2, the vertical line and the cross were presented in the same block of trials so as to be dealt with a common attentional strategy. In Experiments 3 and 4, the no-go target was a 45º rotated cross inside a ring to increase the difficulty of the discrimination. No evidence was obtained that the cross was forward masked by the cue nor that it demanded less attention to be discriminated from the small ring. There was a facilitation of responsivity by the cue when the small ring was replaced by the rotated cross. The results suggest that when the discrimination to be performed is too easy the cue does not mobilize attention.

Influence of separate and mixed experimental designs on reaction times to two simple visual stimuli.

“…The overall absence of difference between reaction times to the line and the cross in both testing sessions of this experiment replicates and extends previous results obtained in our laboratory (Azevedo et al, 2001;Macéa et al, 2006). As already mentioned, similar reaction times to the two stimuli have been obtained in the first testing session of other experiments by our group.…”

“…Considering previous evidence from our laboratory (Macéa et al, 2006), similar reaction times were expected for the line and the cross in the first testing session and, possibly, the second as well.…”

“…The same type of task design influence has been shown in reports by Azevedo, Squella and Ribeiro-doValle (2001) and by Macéa, Abbud, Lopes-de-Oliveira and Ribeiro-do-Valle (2006). They observed that the reaction time to a vertical line inside a ring in a go/nogo visual task did not differ from the reaction time to a cross inside a ring when these stimuli were presented in separate blocks of trials.…”

“…Perhaps this concern could be alleviated by the fact that at least for the first testing session exactly the same result was obtained with 12 other volunteers in a previous study of our laboratory (Macéa et al, 2006). It could also be questioned whether the advantage (of the order of 20 ms) in the discrimination of the cross would have any biological meaning.…”

“…If one considers, however, that exactly the same results were obtained for the first testing session in two previous studies of our laboratory (Azevedo et al, 2001;Macéa et al, 2006) in which 24 volunteers were used (12 in each study) and each one of these volunteers was tested with both stimuli (half of them in each study with the line first and the other half with the cross first, to control for order effects) these doubts should be alleviated.…”