Difference waves for contour minus no-contour conditions.

<p>The graphs are obtained by subtracting the no-contour conditions (dotted lines in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0025151#pone-0025151-g003" target="_blank">Figure 3</a>) from the contour conditions (full lines in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0025151#pone-0025151-g003" target="_blank">Figure 3</a>).</p

Example stimuli for the different array types.

<p>By rotating the elements of the contour condition (left column), the embedded contour perceptually disappears (middle column). Top row: Iso-oriented array, in which all elements surrounding the contour have the same orientation. Bottom row: Randomly-oriented array, in which the surrounding elements have a random orientation. Catch trials (right column) consist of the same stimuli with a small circle overlaid at a random location (here only illustrated for no-contour stimuli). Catch trials are not included in the analyses.</p

Electrodes of interest.

<p>(a) Topographic maps representing the temporal evolution of the difference between the contour and the no-contour conditions (aggregated over iso-oriented and randomly-oriented displays). The electrodes in the significant cluster are highlighted. (b) Spatial layout of the 15 electrodes of interest, with their corresponding labels.</p

Condition-specific grand average ERPs.

<p>Grand mean ERPs (n = 12), averaged over the 15 electrodes of interest (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0025151#pone-0025151-g002" target="_blank">Figure 2b</a>). Full lines represent conditions with an embedded contour; dotted lines represent conditions without an embedded contour. Blue: Iso-oriented conditions. Red: Randomly-oriented conditions.</p

Summary of the repeated-measures ANOVAs on the mean amplitudes and peak latencies for the P1, N1, and P2 components.

<p>Summary of the repeated-measures ANOVAs on the mean amplitudes and peak latencies for the P1, N1, and P2 components.</p

Age distributions of participants in both experiments.

<p>The age distribution for the2-AFC task are presented on the left and for the 4-AFC on the right.</p

Full screen examples of the stimuli in the 2-AFC and the 4-AFC task.

<p>Panel (A) shows a practice trial of the 2-AFC task with line-interleaved elliptic dots. Right side shows the target stimulus: a squared patch standing out in depth from the background. Left side shows the distractor stimulus with only one depth plane. In addition to the disparity difference the target area is also presented in red. This colour/luminance cue is removed after the practice trials. (B) Example of the 4-AFC task with the target stimulus in the right upper quadrant. See dimensions in the main text.</p

Experiment duration for different trial numbers, for the 2-AFC task (red solid line) and the 4-AFC task (blue dotted line).

<p>Experiment duration for different trial numbers, for the 2-AFC task (red solid line) and the 4-AFC task (blue dotted line).</p

Boxplot of stereothresholds (log₁₀ arcsec) in 2-AFC and 4-AFC task (thresholds below 500 arcsec only).

<p>Boxplot of stereothresholds (log₁₀ arcsec) in 2-AFC and 4-AFC task (thresholds below 500 arcsec only).</p

Illustration of simulation procedure for a 4-AFC paradigm.

<p>A) Model function used in this example (model threshold <i>θ</i> = 1.6 log₁₀ arcsec). Each staircase (B) follows the rules described in the main text: starting at 3 log₁₀ arcsec, decreasing the disparity by 0.15 log₁₀ arcsec after a correct answer and increasing disparity by 0.45 log₁₀ arcsec after an incorrect answer. Each row in (B) shows an example of one simulation with 80 trials. The left plots in (B) show the staircases: the ‘presented’ disparities for each simulation of the 80 trials. The right plots show the probability correct as a function of disparity, with the dots being the simulated data and the line the fitted psychometric function to the simulated data. From this fitted psychometric function the threshold value was estimated. After 10000 repeats, the estimated thresholds can be presented in an histogram (C) to show the distribution of likely thresholds that can result from the 4-AFC staircase procedure with this model psychometric function (A). The average of this ditribution can be compared with the model threshold as an indication of bias and precision of the 4-AFC staircase procedure.</p