When one race is not enough: Introducing the relay model to explain multisensory response times

Description

Responses to bimodal signals are typically faster than to unimodal ones, a phenomenon known as the redundant signals effect (RSE). Raab’s (1962) race model explains this by positing two parallel decision processes, with responses being triggered by the faster of the two. Despite its simplicity, the model largely predicts the speed-up of responses when stimulus timing or signal strength are manipulated. However, Miller (1982) showed that observed RSEs often exceed race model predictions, resulting in systematic violations of the race model inequality (RMI). These violations have traditionally been interpreted as evidence against race models, casting doubt on their ability to capture multisensory decision-making. We introduce the relay model, a novel extension of Raab’s framework that reconciles these findings. Here, two race units operate sequentially: the first provides a start signal for the second. This small modification retains the race model’s predictive power while naturally accounting for RMI violations. Constrained only by unimodal response time distributions, the relay model captures all critical aspects of the RSE, with RMI violations emerging as an intrinsic feature of relay-based processing. This framework offers a refined view of multisensory decision-making and highlights a simple, biologically plausible mechanism that may underlie apparent violations of classical models.

Period	11 Jul 2025
Event title	Joint Experimental Psychology Society and Canadian Society of Brain Behaviour and Cognitive Science Meeting: Joint July 2025 Meeting
Event type	Conference
Location	Dundee, United KingdomShow on map
Degree of Recognition	International