Is mental effort exertion contagious? A replication study

Daily, we perform activities in the presence of others (e.g., office work). While it's well-established that the mere presence of others can influence our performance, it is less clear whether others' performance, rather than just their presence, influences us. To address this, we performed a replication of Desender et al.’s (2015) study, Is mental effort contagious?, and conducted a second experiment to follow up on our failure to replicate their findings. Desender et al. used a modified joint Simon task where two participants performed side by side. The manipulated participant completed an easy (mostly congruent trials) and a difficult (mostly incongruent trials) block, while the neutral participant completed two neutral blocks (equal proportion of congruent and incongruent trials). They found that the neutral participant mirrored the manipulated participants’ mental effort, exerting more effort when the latter performed a difficult versus an easy task. In both Experiment 1 (exact replication; N = 176) and Experiment 2 (more demanding joint Simon task; N = 120), we failed to replicate this result despite the fact that the manipulated participants adjusted their mental effort as expected. We identified several methodological concerns regarding the original study, such as participants' limited visibility of each other's physiological signs, hindering their ability to infer mental effort. Moreover, the original study’s effect vanished when re-analyzed with a more robust linear mixed model, suggesting their findings may not have been as reliable as initially thought. Our findings underscore the need for rigorous experimental designs and analyses in psychological research.