Experiment 1: stimuli and results.

<p>a. Pairs of auditory and visual stimuli presented in synesthetically congruent (top) and incongruent trials (bottom) in Experiment 1. b. Psychometric functions describing performance on synesthetically congruent (continuous line) and incongruent (dashed line) conditions in Experiment 1. Filled and empty circles represent the proportion of “auditory second” responses for each SOA tested averaged over all participants of Experiment 1. c. Scatter and bagplot <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0005664#pone.0005664-Rousseeuw1" target="_blank">[39]</a> of participants' sensitivity (JNDs) on congruent vs. incongruent trials (log-log coordinates). Points below the identity line indicate a stronger coupling of congruent stimuli. The cross at the centre of the bag represents the depth median. d. Sensitivity of participants' responses (JNDs) on congruent and incongruent trials in log scale. The central lines in the boxes represent the median JND, the boxes indicate the first and third quartiles, and the whiskers, the range of the data.