Age-related differences during visual search: the role of contextual expectations and top-down control mechanisms.
In visual search, the cognitive system controls the contextual information available by inhibiting irrelevant information to successfully orient attention towards the search target. As cognitive control is reduced in older adults they often experience more difficulties in such tasks. In two eye-tracking experiments, we investigated the interplay between contextual expectations and cognitive control during visual search in naturalistic scenes. A younger and an older group of participants had to find a target object varying in consistency with the search scene (e.g., a basket of bread vs a clothes iron in a restaurant scene) after being primed with contextual information either congruent or incongruent with it (e.g., a restaurant vs a bathroom), and administered as a scene (Experiment 1) or a word (Experiment 2, which included a scrambled word as neutral prime). Participants also completed two cognitive control tasks (Stroop and Flanker) to assess their cognitive control. Older adults had greater difficulty than younger adults with inconsistent objects, especially when primed with congruent information (Experiment 1), or a scrambled word (neutral condition, Experiment 2). Congruent expectations boost distractor objects which have to be suppressed when the semantics of the target object violates them. Neutral primes acted as low-level perceptual distractors that increased the attentional load of participants and needed to be suppressed. Higher cognitive control, especially in older participants, improved the search accuracy in these experimental conditions, but it did not mediate the eye-movement responses. These results shed new light on the links between cognitive control and visual attention in ageing.