On the emergence of the in–out effect across trials: two items do the trick

Individuals prefer letter strings whose consonantal articulation spots move from the front of the mouth to the back (e.g., BAKA, inward) over those with a reversed consonant order (e.g., KABA, outward), the so-called in–out effect. The present research explores whether individuals hold an internal standard or scheme of consonant order that triggers this effect. If this were the case, the in–out effect should already occur in one-trial between-subjects designs. If not, the in–out effect should emerge over the course of trials in within-subjects designs. In Experiments 1a–e (1b–e preregistered; total N = 2973; German, English, and Portuguese samples) employing a one-trial between-subjects design, no in–out effect was found. In Experiment 2 (N = 253), employing within-subjects designs with either 1, 5, 10, 30, or 50 trials per consonant order category (inward vs. outward), the in–out effect was absent in the first trial, but already surfaced for the first 2 trials, reached significance within the first 10 trials and a solid plateau within the first 20 trials. Of the four theoretical explanations, the present evidence favors the fluency/frequency and letter-position accounts and is at odds with the eating-related embodiment and easy-first accounts.