The Effect of Ageing on Optimal Integration of Conflicting and Non-Conflicting Visual-Haptic Stimuli

Multisensory integration typically follows the predictions of a statistically optimal model whereby the contribution of each sensory modality is weighted according to its reliability. Previous research has shown that multisensory integration is affected by ageing, however it is less certain whether older adults follow this statistically optimal model. Additionally, previous studies often present multisensory cues which are conflicting in size, shape or location, yet naturally occurring multisensory cues are usually non-conflicting. Therefore, the mechanisms of integration in older adults might differ depending on whether the multisensory cues are consistent or conflicting. In the current experiment, young ( n = 21) and older ( n = 30) adults were asked to make judgements regarding the height of wooden blocks using visual, haptic or combined visual-haptic information. Dual modality visual-haptic blocks could be presented as equal or conflicting in size. Young and older adults' size discrimination thresholds (i.e., precision) were not significantly different for visual, haptic or visual-haptic cues. In addition, both young and older adults' discrimination thresholds and points of subjective equality did not follow model predictions of optimal integration, for both conflicting and non-conflicting cues. Instead, there was considerable between subject variability as to how visual and haptic cues were processed when presented simultaneously. This finding has implications for the development of multisensory therapeutic aids and interventions to assist older adults with everyday activities, where these should be tailored to the needs of each individual.