Shifting and zooming through space … or not: The role of attention in spatial compatibility tasks - A replication of Stoffer (1991)

The mechanism underlying the Simon effect remains debated, with two prominent theories – the attention-shifting account (Stoffer, 1991) or the referential coding account (Hommel, 1993) – offering competing explanations. To date, neither account can fully explain all available empirical data. Most published studies rely on limited sample sizes, which constrains statistical power and leaves the field without conclusive evidence. This study directly replicated Stoffer’s (1991) investigation into attentional subprocesses that generate the Simon effect. We manipulated target spatial position across two reference frames: a global frame based on target’s screen side and a local frame defined by the relative position within each screen side, allowing us to test for both global and local Simon effects. Targets were presented inside precues, either a large box or two small boxes, which were presented simultaneously with or sequentially before the target. With an adequately-powered sample, our study revealed concurrent global and local Simon effects – a result absent from Stoffer’s original findings. Only the local Simon effect varied with precue type and simultaneous or sequential target presentation. These results clarify the conditions under which attentional shifting and referential coding mechanisms contribute to different Simon effects, demonstrating that when spatial target positions are defined by both global and local reference frames, these mechanisms shape the emergence of distinct Simon effects in different ways.