Time course of a typical trial of the go/no-go task.

<p>In each trial, an initial word cue indicated one of four possible hand gestures (‘OK’, ‘Peace’, ‘Thumbs-Up’, ‘Point’). Participants prepared and performed the cued gesture with their right hand as quickly as possible in response to ‘Go’ cues (67% of trials), and withheld responses to ‘No-go’ cues (33%). ‘Go’ cues consisted of a static image of a hand gesture that either matched (congruent) or did not match (incongruent) the cued and executed action, presented either in the egocentric perspective or in the allocentric perspective. Reaction times (RTs) were measured. After performing the action, participants were required to report either the action they had just performed (action context), or the action they had just seen (image context) and to select the correct response among the four possible gestures.</p

Summary of interference effects in milliseconds.

<p>RTs for congruent gestures, RTs for incongruent gestures, difference and the T-test value. Numbers in brackets indicate standard deviation. Asterisks indicate p<.01.</p

Mean absolute metric error (±1 standard error) for the poor navigators, plotted separately for the three different secondary task conditions and the control condition (without interference).

<p>Mean absolute metric error (±1 standard error) for the poor navigators, plotted separately for the three different secondary task conditions and the control condition (without interference).</p

Schematic of the virtual environment used in the navigation task.

<p>(a) Example display of the virtual environment during the encoding phase of an experimental trial. Landmarks are shown in red, green and blue. The target is shown in yellow, with a virtual light beacon projecting vertically from its apex. (b) Sequence of events in a typical experimental trial. Participants entered the environment and navigated to the target before pressing a button on the joystick to indicate when they reached its location. The encoding phase was followed by a delay period (11 seconds), in which participants were asked simply to remember the object's location (control task), or they were asked to perform one of three secondary tasks (visual, verbal or spatial). In the subsequent retrieval phase, participants re-entered the arena from a different location than in the encoding phase (shifted by 90°, 180° or 270°, with equal probability). They were required to navigate to the location of the target, which was now absent from the display, and to indicate via the joystick when they had arrived there. The next trial commenced after a further delay of 3 seconds.</p

Example trial sequence from Experiment 1 (top) and all tested target locations (bottom).

<p>In this example, the participant first fixates the top left spot for the first two frames and is then required to make a saccade towards the green spot at the same time as the onset of the cue (square frame). In this example, the target (the tilted bar) appears at the retinotopic location of the cue, but can actually appear at any target location shown in the bottom panel. Note there was only one target presented per trial, all targets and cues were grey, and the background of the display was black.</p

Experiment 2 response-time analyses according to probe-saccade onset asynchrony.

<p>According to probe-saccade onset asynchrony, trials were sorted into 100 ms time bins. Response time differences between test and control locations were then calculated for each condition at each time interval, with positive values indicating faster responses to targets at test than control locations. No changes in response times across time bins were found.</p

Experiment 2 saccadic latency distributions.

<p>Frequencies are plotted on the y-axis, and mean saccadic latencies are plotted on the x-axis (vertical lines). Color codes correspond to those used in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0045670#pone-0045670-g006" target="_blank">Figure 6</a>, with solid lines representing test conditions and dotted lines representing control conditions. Asterisks indicate significant differences between means. *p<0.10; **p<0.05.</p

The basic arrangement of stimuli employed in the current experiments, adapted from Mathôt and Theeuwes [<b>1</b>].

<p>Participants made a saccade from a grey spot to a green spot, as indicated by the arrow. Prior to the saccade, a cue (the black square) was briefly flashed. Shortly following the offset of the cue and still prior to the saccade, a target was shown at locations represented by the tilted bars. In Mathôt and Theeuwes' study, the target appeared at the retinotopic or future-field location of the cue, or one of their relative control locations (the broken tilted bars). In the present study, we also probed several intermediate locations.</p

Experiment 1 error rates and saccadic latencies (ms).

<p>Experiment 1 error rates and saccadic latencies (ms).</p

Experiment 1 response-time results.

<p>The left panel depicts absolute response times for all conditions. The right panel shows the response time differences between test and control locations, with positive values indicating faster responses to targets at test than control locations. Error bars represent standard error. Asterisks indicate that differences are different from 0. *p<0.10; **p<0.05.</p