Age-related changes in perceptual and top-down components of visual search

Background

A core component of active vision is the ability to search for objects in the scene. This might entail finding your phone on your desk or the link on this website to volunteer for this study. While we rarely consider what is involved, research has shown search is a complex process that involves the integration of sensory visual input with cognitive abilities, such as short- and long-term memory. These abilities are affected by ageing, with changes in the visual pathway and brain affecting the quality and speed of sensory information, the capacity of short-term memory and the ability to maintain proactive control during the planning and execution of eye movements. In many cases, older observers compensate for these changes by relying on their experience to predict when and where visual objects are likely to be found. In some situations, however, they may not be familiar with objects in the scene or know where they are most likely to occur.

Study Objectives

The objective of this project is to investigate the impact of normal ageing on different sensory and cognitive components of visual search. Understanding the way ageing impacts sensory and cognitive processes during search, will provide important insights into the best ways to design visual displays and search strategies that maintain and support fast and accurate search in different situations for older adults.

Methods

The project includes several studies that use different techniques to measure the impact of age on visual search. Eye movement recordings provide a rich source of information about where and when people fixate different objects in response to information about the target’s identity (i.e., its colour and shape). How many fixations are made, and the type of strategies observers use to guide eye movements are determined by the resolution and extent of sensory information obtained in a single fixation, as well as the observer’s ability to maintain and use information about the features that distinguish the target from other objects (often called distractors) during search.

This project will extend previous work from our lab by integrating eye movement recording with electrophysiological measures of fixation-related potentials. To do this, we will compare eye movement patterns in young and older adults using an infrared camera that tracks the position of the eye relative to objects on computer screen during search. Electrodes placed on the head will also record changes in the polarity of populations of neurons during fixations to objects in the display. Comparisons of fixation-related potentials for objects that vary in terms of their similarity to the target, provide an index of the neural signals involved in the selection and evaluation of objects during visual search.

The image on the right depicts a display containing subsets of blue and red objects. The lines and numbers on the image illustrate the pattern of eye movements (saccades) and fixations during search. Prior to search, the observer is asked to detect a red object with a gap at 90 or 270 degrees.

The data indicate the observer’s eye movements were highly selective, with saccadic sampling restricted to the subset of objects that could contain the target. Search in this case, is guided by the observers' ability to discriminate and prioritise relevant over irrelevant objects during the planning and execution of saccades.

In this study, we will be investigating how ageing affects the amplitude of fixation-related potentials to different objects as well as observers' ability to discriminate and prioritise subsets of objects during search.

Getting Involved

We are currently recruiting participants for this study. Participants will be invited to the George Davies Centre on University of Leicester’s city campus and sessions will involve completing some questionnaires, visual screening (acuity charts) and computer-based visual search tasks. Participants will receive Amazon vouchers (£11.00 p/hour) and sessions will take between 1.5 and 3 hours, depending on the study.

If you are interested in taking part, or would like more information about the project, please use the form below. You can also e-mail Milena (mvr2@le.ac.uk) directly.

Study Team

The study is being conducted by a team of researchers and PhD students at the University of Leicester's School of Psychology and Vision Sciences.

First Name Last Name Email Address Role
Doug Barrett djkb1@le.ac.uk Principal Investigator
Milena Rota mvr2@le.ac.uk PhD Student
Tahani Alqahtani ta259@le.ac.uk PhD Student

Funding

The project is supported by a 4 year PhD studentship funded by the BBSRC via the Midlands Integrated Biosciences Training Partnership.

More Information

The article below reports the results of a study that used cues to manipulate the availability of information about the target’s colour to compare the impact of prior information on selectivity of eye movements during search in young and older adults. The results reveal an age-related decline in the use of short-term memory to guide eye movements during search. This leads to a less effective search strategy in older adults, which is likely to impact the efficiency of everyday activities, such as driving or selecting items during online shopping.

Barrett, D.J.K., Hutchinson, C V., Zhang, F., Xie, H & Wang, J. (2024). Age-related differences in saccadic indices of top-down guidance via short-term memory during visual search. Psychology & Aging. Online First Posting.

Here is a press release that reports the study's findings and potential implications for older adults' use of digital technology.

If you would like to know more about the lab's work, see our other pages here.