We are interested in how our perception of visual stimuli can be altered by presenting the stimuli of interest against a different background or context. For example, we have previously demonstrated contextual effects on contrast – where the contrast of a pattern appears to be less than its physical contrast when surrounded by a similar pattern but of higher contrast. Similar contextual effects are also seen when we test other fundamental visual features, such as luminance (brightness), orientation (tilt) and flicker. For example, a grey patch appears darker when placed on a bright background, and vice versa (also known as the ‘simultaneous brightness illusion’, see figure below).
Some contextual effects (e.g. contrast) have been studied extensively in younger and older observers to understand how normal, healthy ageing affects our visual perception. For the first time, we have tested a range of contextual effects (luminance, contrast, flicker and orientation) in the same observers to investigate whether the healthy ageing process results in consistent or selective alterations to visual perception. Performance on these contextual tasks is highly relevant to real-world functioning where objects of interest are rarely presented on uniform backgrounds in isolation. We find that in older adults, relative to younger adults, perceptual judgements about the luminance, contrast, depth of flicker and orientation of a visual stimulus are more strongly affected when non-uniform backgrounds are introduced. However, the strength of contextual effect on one task does not necessarily predict performance on all other tasks, which suggests that there is not one single, unifying mechanism for the range of contextual effects observed.
You can read the full version of the paper in Frontiers in Aging Neuroscience here.