Global and Local Biases and Biological Motion Processing in Health Ageing

The ability to perceive biological motion has been shown to deteriorate with age and it is assumed that older adults rely more on the form than the local motion information when processing point-light walkers. Recently, it has been suggested that biological motion processing in ageing is related to a form-based global processing bias (Insch et al 2012, Experimental Ageing Research, 38, 169-185). Here, we investigated the relationship between older adults' preference for form information when processing PLWs and an age-related form-based global processing bias. In a first task, we asked older and younger adults' to sequentially match three different point-light actions. On each trial, participants were first presented with a normal action that contained local motion and global form information, a scrambled action that contained primarily local motion information, or a random-position action that contained primarily global form information. The second stimulus was always a normal action. Participants had to indicate whether the two sequentially presented actions were the same or different. Our results show a main effect of walking condition, and an interaction between walking condition and age, as older adults performed worse for the scrambled actions. In a second task, we investigated form-based global processing biases using the Navon task and analysis revealed a general relationship between the Navon task and the processing of scrambled walkers