Investigating Multi-Sensory Integration in the Estimation of Distance Traveled

Traversed distance perception involves estimating the extent of self-motion as one travels from one position in space to another. It is a multi-modal experience in which information from both visual flow and locomotor cues (i.e. proprioceptive, efference copy and vestibular cues) jointly specify the magnitude of self-motion. While recent evidence has demonstrated the extent to which each of these cues can be used independently to estimate traversed distance, relatively little is known about how they are integrated when simultaneously present. Here, a series of studies conducted in both virtual and real-world environments show that humans use a combination of visual flow and locomotor cues to estimate distance traveled. During walking the presence of visual flow results in a relative underestimation of distance traveled compared to circumstances in which it is absent (blindfolded walking). When visual gain is manipulated during walking, thus causing an incongruency between the two cues, locomotor cues appear t o be weighted higher overall. This is true in environments consisting of a rich visual scene (real world) and those in which visual flow is isolated (VR)