Congruency and distance effects vary across simultaneous and sequential two-digit integer, fraction, and decimal 2AFC...

Two-alternative forced choice (2AFC) comparison tasks are widely used to investigate how humans process complex information. However, it is still not fully understood how the format of these tasks influences cognitive strategies. In this study, we analyzed whether 2AFC tasks with simultaneous stimulus presentation provide the same information on how people process information as 2AFC tasks with sequential stimulus presentation. We investigated this question within the number domain. In particular, we investigated how the distance and congruency effects-which are interpreted as behavioral markers of holistic and fragmented number processing-vary across simultaneous and sequential versions of two-digit integer, fraction, and decimal 2AFC tasks. Undergraduate students (n = 162) completed both simultaneous and sequential versions of two-digit integer, fraction, and decimal comparison tasks. Comparison pairs varied in numerical distance (near vs. far) and congruency (congruent vs. incongruent). Across all number types, we observed both distance and congruency effects. However, these effects differed by task format. In particular, a linear mixed model revealed that the congruency effect was stronger in simultaneous tasks with near-distance pairs and weaker in sequential tasks with far-distance pairs. The differences in the strength of the distance and congruency effects across simultaneous and sequential 2AFC task formats indicate that they play a critical role in shaping information processing strategies. Thus, our findings suggest that simultaneous and sequential 2AFC tasks engage distinct cognitive processes and should not be used interchangeably in cognitive research.