Inhibition of return, gap effect and saccadic reaction time to a visual target

Abstract

Simple manual reaction time (MRT) to a visual target (S2) is shortened when a non-informative cue (S1) is flashed at the S2 location shortly before the onset of S2 (early facilitation). Afterwards, MRT to S2 appearing at the S1 location is lengthened (inhibition of return -IOR). Similar results have been obtained for saccadic reaction time (SRT). Moreover, when there is a temporal gap between offset of the fixation point (FP) and onset of a target (gap paradigm), SRT is shorter than SRT in an overlap paradigm (FP remains on). In the present study, we determined SRT to S2 (10º) after presenting S1 at the same eccentricity (10º) or at a parafoveal position (2º) in the same or in the opposite hemifield. In addition, we employed both gap and overlap paradigms. Twelve subjects were asked not to respond to S1 (2º or 10º) to the right or to the left of FP, but to respond by making a saccadic movement in response to S2. We obtained the following results: 1) a 40-ms gap effect, 2) an interaction between gap effect and IOR, 3) a 39-ms delay (IOR) when S2 appeared at the cued (S1) position, and 4) a smaller (17 ms) but significant inhibition when S1 occurred at 2º in the ipsilateral hemifield. Thus, a parafoveal (2º) S1 elicits an inhibition of SRT towards ipsilateral peripheral targets. Since an inhibition of the ipsilateral hemifield by a 1º eccentric cue has been reported to occur when manual responses are employed, we suggest that the postulated functional link between covert and overt orienting of attention is also valid for parafoveal cues.

The gap effect reduces both manual and saccadic inhibition of return (IOR)

“…Our results contrast with those of Abrams and Dobkin ( 1994 ) and Guimaraes-Silva et al ( 2004 ), both of whom showed an increase of saccadic IOR after the 200 ms gap. The cause of this discrepancy is unclear and worthy of further research, but we speculate that it may have arisen mainly for procedural reasons.…”

“…The decrease of saccadic IOR and manual IOR due to the 0 ms gap contradicts the results obtained in similar studies in which the “pure” gap effect (200 ms gap) was applied (Abrams and Dobkin 1994 ; Guimaraes-Silva et al 2004 ; Hunt and Kingstone 2003 ; Souto and Kerzel 2009 ). Therefore, we conducted a second experiment in which we used the 200 ms instead of the 0 ms gap paradigm.…”

“…Moreover, Abrams and Dobkin ( 1994 ), also in a 200 ms gap paradigm, demonstrated the opposite to Hunt and Kingstone’s ( 2003 ) pattern of saccadic IOR: the disappearance of the fixation point increased IOR. This result was later replicated by Guimaraes-Silva et al ( 2004 ). According to Souto and Kerzel ( 2009 ), in the case of saccadic IOR, these discrepancies in results suggest that both types of gap could engage different processes.…”

“…We conducted a more typical IOR procedure than that of Abrams and Dobkin and Guimaraes-Silva et al Abrams and Dobkin’s results are considered unusual and are, therefore, probably responsible for the surprising lack of IOR in the fixation condition, in which ordinarily a reliable IOR effect is observed (Hunt and Kingstone 2003 ; Klein and Hilchey 2011 ). In the study of Guimaraes-Silva et al ( 2004 ), the same stimulus (green light-emitting diodes) had different functions (i.e., cue, target, and fixation point). Use of this kind of stimuli set has been criticized as it can cause some perceptual confusion and, in consequence, impact the participants’ response strategy (Klein and Hilchey 2011 ).…”

Perceptual and motor inhibition of return: components or flavors?

“…Whereas this confound does not challenge the different pattern of results we obtained in the blocked versus mixed conditions, one may wonder whether the removal of fixation might have reduced the measured magnitude of IOR for peripherally presented targets in our mixed condition, thus obscuring a pattern of results that would be consistent with the two-components view. This possibility can be entertained, despite Abrams and Dobkins (1994a) finding of increased IOR following fixation removal (see also Guimaraes-Silva, Gawryszewski, Portugal, & Klausner-de-Oliveira, 2004), because other researchers (Hunt & Kingstone, 2003;Souto & Kerzel, 2009) have reported the opposite finding (that fixation removal can decrease IOR). Because the possible contribution of fixation removal in Experiment 1 is, on the basis of the literature, ambiguous, Experiment 2 was conducted to determine whether IOR would continue to be equivalent for peripherally and centrally presented targets in a mixed design when the fixation removal confound was eliminated (a fixation stimulus remains onscreen throughout the trial on both peripheral and central trials).…”