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Evaluating the contributions of age-related changes in sensory acuity and cognitive control on the speed and accuracy of visual search

Primary Supervisor: Dr Doug Barrett, Department of Neuroscience, Psychology and Behaviour

Secondary supervisor: Claire Hutchinson

PhD project title: Evaluating the contributions of age-related changes in sensory acuity and cognitive control on the speed and accuracy of visual search

University of Registration: University of Leicester

Project outline:

The ability to identify and locate task-relevant objects in the scene is a key component of functional vision. In psychology and human neuroscience, this ability has been investigated using visual search tasks, which measure the speed and accuracy of detection for a target among a variable number of non-target (distractor) stimuli. A substantial body of evidence indicates normal ageing is associated with declines in the speed and accuracy of search. Previous research suggests these reflect age-related reductions in the quality of sensory input [1], a general slowing of processing, or impairment in the ability to weight relevant over irrelevant sensory information during the selection and evaluation of visual stimuli (see [2] for a review).

Empirical evidence to support theoretical accounts of age-related decreases in search performance is mixed. Contradictory findings reflect heterogenous samples and different measures used to investigate age-related changes in search. Studies investigating age-related changes in sensory acuity rarely test cognitive mechanisms associated with the evaluation of competing visual input, short-term memory or the planning and execution of saccades. Studies focussing on age-related changes in cognitive components of search, typically present identical stimuli to young and old observers. Inferences from these studies are likely to confound differences in sensory acuity with changes in cognitive processes, which mediate the speed and accuracy of search.

The objective of the project is to measure the contributions perceptual and cognitive processes to age-related reductions in the speed and accuracy of visual search. To do this, the project will incorporate techniques including psychophysics, cognitive modelling and eye movement recording to quantify the impact of ageing on target representation, guidance, selection, and identification during search [3]. The study will recruit a cohort of young (< 25 years) and older (> 65 years) observers to a series of visual search experiments using displays containing visual optotypes and selected natural images. The aims of the project will be:

  1. Quantify age-related changes in sensory acuity using standard optometric tests and psychophysical techniques to measure contrast, spatial frequency and chromatic sensitivity for stimuli across the visual field [4].
  2. Apply cognitive models to evaluate different accounts of age-related changes in search accuracy for displays containing stimuli titrated to match sensory acuity in young and older observers.
  3. Use Bayesian Ideal Observer estimates to predict the probability of observers fixating display objects based on their physical relationship to the search target. Rates of re-fixation and decision times for fixated objects will be used to provide additional information about age-related changes in observers’ ability to select, evaluate and maintain visual information during search.
  4. Develop a technique to map spatial priors on natural scenes to model the impact of short- and long-term memory and observers’ experience on the weighting of relevant and irrelevant information during saccadic sampling and target detection.
  5. Use pupillometric recordings of task-related changes in pupil size to contrast cognitive effort and sustained attention in young and older observers in response to changes in the perceptual discriminability of displays, task instructions and prior experience [6].  

The project will be supervised by a multidisciplinary team with expertise in experimental psychology, optometry, cognitive modelling and eye movement recording. The student will synthesise physiological and behavioural measures of search with predictive quantitative models to evaluate different theoretical accounts of the impact of ageing on visual search. The results will provide clinically relevant insights into the relative contributions of age-related changes in sensory acuity and cognitive processes that have important implications for the independence and safety of older adults.

References:

  1. Veiel, L. L., Storandt, M., & Abrams, R. A. (2006). Visual search for change in older adults. Psychology and aging, 21(4), 754.
  2. Zanto T.P. & Gazzaley, A. (2014). Attention and ageing. In A.C Nobre & S. Kastner (Eds.), The Oxford handbook of attention (pp. 927-971). Oxford University Press.
  3. Eimer, M. (2014). The neural basis of attentional control in visual search. Trends in cognitive sciences, 18(10), 526-535.
  4. Arena, A., Hutchinson, C.V., Shimozaki, S.S., Long, M.D. (2013). Visual discrimination in noise: behavioural correlates of age-related cortical decline. Behavioural Brain Research, 243, 102-108.
  5. Barrett, D.J.K., Shimozaki, S.S., Jensen, S., & Zobay, O. (2016). Visuospatial working memory mediates inhibitory and facilitatory guidance in preview search. Journal of Experimental Psychology: Human Perception and Performance, 42(10), 1533.
  6. Barrett D.J.K., & Pilling, M. (2019). Behavioural and pupillometric evidence for feature-specific resources in visual short-term memory. Abstracts of the 20th European Conference on Eye Movements, 18-22 August 2019, in Alicante (Spain). Journal of Eye Movement Research, 12(7).

BBSRC Strategic Research Priority: Understanding the Rules of Life: Neuroscience and behaviour & Systems Biology: Integrated Understanding of Health: Ageing

    Techniques that will be undertaken during the project:

    • Optometric visual tests
    • Visual psychophysics
    • Cognitive modelling
    • Pupil dilation and eye movement recording

    Contact: Dr Doug BarrettLink opens in a new window, University of Leicester