Abstract
One of the core mechanisms involved in the control of saccade responses to selected target stimuli is the disengagement from the current fixation location, so that the next saccade can be executed. To carry out everyday visual tasks, we make multiple eye movements that can be programmed in parallel. However, the role of disengagement in the parallel programming of saccades has not been examined. It is well established that the need for disengagement slows down saccadic response time. This may be important in allowing the system to program accurate eye movements and have a role to play in the control of multiple eye movements but as yet this remains untested. Here, we report two experiments that seek to examine whether fixation disengagement reduces saccade latencies when the task completion demands multiple saccade responses. A saccade contingent paradigm was employed and participants were asked to execute saccadic eye movements to a series of seven targets while manipulating when these targets were shown. This both promotes fixation disengagement and controls the extent that parallel programming can occur. We found that trial duration decreased as more targets were made available prior to fixation: this was a result both of a reduction in the number of saccades being executed and in their saccade latencies. This supports the view that even when fixation disengagement is not required, parallel programming of multiple sequential saccadic eye movements is still present. By comparison with previous published data, we demonstrate a substantial speeded of response times in these condition (“a gap effect”) and that parallel programming is attenuated in these conditions.
Highlights
To carry out everyday visual tasks efficiently and effectively, we make multiple sequential eye movements
The results are presented in two sections: First, we examine the evidence for parallel programming of saccade sequences across the levels of prior information and second confirm the presence of a gap effect
From left to right on each graph in the figure, results show performance as the amount of prior information about the target locations is restricted from all seven targets displayed simultaneously, to only the five or three targets displayed at any one time, to to the target only being revealed when a saccade was executed to the preceding target
Summary
To carry out everyday visual tasks efficiently and effectively, we make multiple sequential eye movements. Empirical research that has examined this in more strictly controlled experimental visual environments has been largely limited to tasks where two or three saccade responses have been made or saccade sequences have been pre-planned (Becker and Jürgens 1979; Godijn and Theeuwes 2002, 2003; McPeek et al 2000; Theeuwes et al 1998) These studies have shown improved performance on tasks that require visual information to be processed at the locations of future saccade targets; a reduced latency of saccadic responses and effects on the saccade metrics (i.e., landing position and trajectory deviations; Baldauf and Deubel 2008; Bhutani et al 2012; De Vries et al 2014; Gersch et al 2004, 2009; McSorley et al 2019; Walker and McSorley 2006).
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