Is four the same as 4? Exploring whether stimulus repetitions or identity repetitions drive voluntary task choice

Though the voluntary task-switching paradigm asks participants to select their task and whether to switch on each trial internally, external bottom-up information from the stimulus affects task choice, such that participants were more likely to switch tasks on stimulus switches than stimulus repetitions (e.g., Mayr & Bell, Psychological Science, 17(9), 774-780, 2006). In previous research, both the perceptual elements and the identity of the stimulus changed on a stimulus switch, producing ambiguity with regard to which of the two changes drove the effect. By intermixing two stimulus types (words and Arabic numerals in Experiment 1; words and dot arrays in Experiment 2), we aimed to disentangle whether stimulus or identity repetitions drive stimulus-based switching. We produced lists with equal numbers of full stimulus repetitions (4 → 4), full stimulus switches (4 → one), and trials where the identity repeated but the stimulus changed (identity repetitions; 4 → four). We replicated the previous finding that participants were more likely to repeat the previous task on a full stimulus repetition than they were with a full stimulus switch. However, identity repetitions were not statistically different from full stimulus switches. These findings indicate that bottom-up perceptual information, rather than stimulus identity, may be what drives stimulus-based switching.