Group average perceptual performance, shown for PSS (left panel) and threshold estimates (right panel) of fitted psychometric functions, respectively.

<p>Diamonds represent predictions for COMBI condition, as expected from average estimates in single cue conditions. Error bars represent within-subject standard errors of mean [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116810#pone.0116810.ref050" target="_blank">50</a>]. Data points for different conditions are shown with small horizontal offsets to increase visibility.</p

Task schematic and exemplary results.

<p><b><i>A</i></b>, Trials started with a fixation cue and a target 10 degree to the left (black lines). After 400 ms of stimulus overlap (shaded area), the fixation was switched off, serving as go signal to perform a saccadic eye movement to the target (exemplary eye trace in horizontal plane, gray line). Saccade onset triggered a target blank for 250 ms (JUMP task), after which the target reappeared with unpredictable offset. Subjects indicated apparent jump direction. <b><i>B</i></b>, In the VISUAL task, subjects kept initial fixation while the peripheral target and an additional flanker object (vertical bar) was presented at one of three distances [at 1.2, 2.8 (this trial) and 4.4 deg left of target; blue continuous, dashed and dotted lines, respectively]. The fixation dot then disappeared and 200 ms later, the target-flanker pair was briefly switched off and reappeared in the center field of view, mimicking the visual consequences of an intervening saccade to the target. Critically, the target-flanker distance was now changed (shown only for actual flanker position with fainter color corresponding to the unchanged relative position) and subjects reported the apparent change in relative position of the flanker with respect to the target. <b><i>C</i></b>, In the COMBI task, stimuli and instructions were identical to the JUMP task, apart from the additional flanker object that was presented together with the target at one of three target-flanker distances [at 1.2, 2.8 (this trial) and 4.4 deg left of target; green continuous, dashed and dotted lines, respectively]. <b><i>D-F</i></b>, Psychometric functions of one naïve subject. Proportion of trials in which subject reported an apparent target jump in saccade direction (forward), plotted against relative displacement levels. Negative values refer to target displacements against saccade direction. Circle sizes represent the number of trials for a given target jump. Cumulative Gaussians were fitted to perceptual response data, separately for different conditions [JUMP (<b><i>D</i></b>), VISUAL (<b><i>E</i></b>), COMBI (<b><i>F</i></b>)] and the three different target-flanker distances in VISUAL and COMBI condition (1.2 deg, continuous lines; 2.8 deg, dashed lines; 4.4 deg, dotted lines). Raw data for medium and large distance are not shown for the sake of clarity.</p

Cartoon of experimental conditions.

<p>In JUMP condition (left), after an unpredictable foreperiod of stable fixation (1200–1600 ms; eye position, white circles) on an initial fixation dot (green), a second dot (blue) appeared 10 deg to left of fixation. After 400 ms stimulus overlap, the fixation dot was turned off, serving as a signal to perform a saccadic eye movement to the second dot. Contingent on saccade onset, the target dot was switched off and reappeared 250 ms later with variable and unpredictable horizontal offset. Subjects performed a perceptual judgment on the apparent jump direction by means of a button press. In the VISUAL condition (middle), the trial started similar to JUMP condition, including the stimulus overlap, but with the exception of a second object (orange vertical bar) that appeared together with the target dot. Subjects kept initial fixation when the fixation cue disappeared and target and flanker object remained on screen for another 200 ms (mimicking saccadic reaction time). Then all cues disappeared for 50 ms (mimicking the visual transient induced by the saccade in JUMP and COMBI condition). Then, first the flanker and then the target reappeared (onset asynchrony, 200 ms, mimicking remaining BLANK duration after saccade in COMBI condition), with target position now coinciding with fixation and flanker position coinciding with previous relative position to target dot plus some variable and unpredictable offset. Here, subjects indicated the apparent relative displacement of the flanker object with respect to the target position. In COMBI condition (right), the task was identical to JUMP condition plus the flanker object of the VISUAL task. This flanker object remained on screen at same position throughout the trial.</p

Extraretinal information contributes to perceptual decisions.

<p><b><i>A</i></b>, Psychometric functions of naïve subject in the JUMP task (same subject as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116810#pone.0116810.g002" target="_blank">Fig. 2</a>; cf., <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0116810#pone.0116810.g002" target="_blank">Fig. 2<i>D</i></a>). Proportion of trials in which subject reported an apparent target jump in saccade direction (forward), plotted against relative displacement levels (filled orange circles and continuous line). In addition, data are replotted as a function of the (binned) visual error experienced after saccade completion (unfilled orange circles and dashed line). <b><i>B</i></b>, Mean group bias (PSS, left panel) and group threshold estimates (right panel) for psychometric functions fitted to perceptual reports with respect to the real target displacement (“real”) and the (binned) visual error experienced after saccade completion (“retinal”). Error bars reflect standard errors of the mean.</p

Average group thresholds for different conditions, after normalizing to unity for the predicted value (unfilled green bar to right).

<p>Error bars represent standard error of the mean. Statistical comparison yielded significant differences for COMBI vs. JUMP and COMBI vs. VISUAL, but no significant difference for COMBI vs. predicted thresholds (two-tailed pairwise t-test on non-normalized data, * <i>P</i> < 0.05; ** <i>P</i> = 0.01).</p

Results.

<p>a. The Rating change between the two sessions is displayed for the eight conditions (resulting from the factors Session 1 Choice/Session 2 Choice, Chosen/Unchosen, Go/No Go) in the positive and negative valence group. There was an effect of Choice (chosen larger than unchosen), that was stronger in the experimental condition (larger in Session 1 Choice than Session 2 Choice). In the positive valence group choosing a picture by action led to increased positive choice-induced preference change (defined as the interaction term of Choice and Condition, see Fig. 2b). This effect was absent in the negative valence group. Note that the overall interaction effect is driven by differences across all conditions, including the Session 2 Choice condition. b. To illustrate the overall interaction, the choice-induced preference change (interaction term of Condition (Session 1 Choice/Session 2 Choice) and Choice (Chosen/Unchosen)) is displayed for choice made by action and inaction in both groups, resulting in four conditions (Choice by action in the positive valence group; Choice by inaction in the positive valence group; Choice by action in the negative valence group; Choice by inaction in the negative valence group). Error bars represent the standard error of the mean.</p

The apparent discounting shift <i>m</i>_<i>a</i>-<i>m</i>_<i>b</i>, considered in the direction of the ‘other’, was regressed against <i>σ_r</i> and <i>u</i> in the whole sample, N = 738.

<p>This shift is plotted against each variable removing the variance predicted by the other. We focused on variable inter-relationships, thus ignoring y-intercept terms. <b>a.</b> Shift vs. reference dispersion <i>σ_r</i>. The bigger the likely distance (<i>σ_r</i>) the smaller the shift. <b>b.</b> Shift vs. preference uncertainty <i>u</i> is also in the direction predicted by Bayesian reasoning. We note that in each case the population consists of a denser core of points but also of penumbrae that slightly dilute the overall fits (coloured lines). Here we follow this more conservative whole-sample regression; see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1004965#pcbi.1004965.s001" target="_blank">S1 Text</a> for post-hoc quality-controlled analyses.</p

Uncertainty-relevance model of preference shift.

<p>Before information about the ‘other’ is seen, beliefs about the reference distribution are uninformative and so the original beliefs about the self are proportional to the likelihood <i>p</i>(<i>d</i>_<i>s</i>; <i>k</i>_<i>s</i>). Once data <i>d</i>_<i>o</i> about the other are seen, the likelihood of <i>k</i>_<i>o</i> combines with the conditional probabilities that <i>k</i>_<i>s</i> and <i>k</i>_<i>o</i> as they are drawn from the reference distribution; this combination multiplies the beliefs about the self to yield the posterior (shifted) <i>k</i>_<i>s</i>. This is a schematic representation of <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1004965#pcbi.1004965.e014" target="_blank">Eq 5</a> (see e.g. its penultimate line).</p

The difference between <i>m</i>-for-self after learning and before learning as a function of partner’s preference.

<p>This difference (ordinate) is plotted against the difference between <i>m</i> -for-other and <i>m</i>-for-self-before-learning. Two clusters form because we exposed participants to others that were 2.3 <i>ln</i> units away in modal preference (in either direction). Red is the identity line (fully adopting other's preference). Green is the linear regression line. It has a positive slope as expected (p ~ 0.0), but a negative intercept, denoting a slight overall bias for shifting towards more patient preferences.</p

Experimental Design.

<p>The experimental paradigm comprised four distinct sessions. In Rating Session 1 subjects rated all images. These images were then paired on the basis of matched ratings. In Choice Session 1 subjects could freely choose (by either pressing or not pressing a button) or a computer chose at random. In Rating Session 2 subject rated all images again while text informed subjects as to what occurred in Choice Session 1. Finally, in Choice Session 2 the pairs the computer chose beforehand in Choice Session 1 were displayed. Subjects freely chose again by performing or omitting a button press like in Choice Session 1. This experiment was conducted in two independent samples with two different stimulus sets (positive and negative valence). Comparing the value change from Rating Session 1 to 2 for chosen and unchosen items before revaluation and after revaluation provided a measure of choice-induced value change. We tested whether this choice-induced value change was modulated by action or inaction (Go/No Go) and by valence. The frequency of choice expressed in a response Go or No Go allows us to test for a bias induced by action on choice itself.</p