Figure : Age distribution of autistic and non-autistic participants.
Apparatus and stimuli. The experiment was programmed and conducted online using the Neurotask platform (www.neurotask.com). Participants completed the task using their own hardware. The stimuli were taken from Hillock-Dun, Grantham, and Wallace (2016) and included videos of an actress saying the syllable /ga/ with either the corresponding audio (for congruent trials) or the audio of the same actress saying the syllable /ba/ dubbed over the video (for incongruent trials). Stimulus onset asynchrony (SOA) was either -500, -260, 0, 260 or 500 ms. Here, negative signifies that audition was leading, and vice versa. All videos lasted 2000 ms.
Procedure . Trials began with a black fixation cross in the center of a white screen for 1000 ms. Subsequently, the video played for 2000 ms. After its conclusion, participants were prompted to make two self-paced responses. First, they were asked whether they heard /ba/, /da/, or /ga/ by pressing either the b, d, or g-key, respectively. Second, they were asked whether the video and audio were synchronized or not by pressing the 1 or 0-key, respectively. The following trial was initiated as soon as the synchrony judgment was given. The two congruency types and five SOAs produced a total of ten unique trial types. After reading the written instructions and completing ten practice trials (one of each stimulus type), participants completed ten repetitions of each trial type, for a total of 100 experimental trials in randomized order. The experiment lasted approximately 7 minutes and was part of a larger battery of online tasks (not reported here). Figure 2 illustrates an example trial sequence.