If college students had to perform in conditions that mimic the perception deficits many older people have, their IQ scores would take a dip.
As people grow older, do they really lose intelligence or is something else happening that drives down IQ scores? It was a question that Case Western Reserve University researchers took into the lab to conduct two coding experiments to test out their hypothesis that older people suffer perception problems that impair their abilities to perform well on intelligence tests.
Grover C. Gilmore, professor of psychology and dean of Case's Mandel School of Applied Social Sciences, led the National Institute of Health-funded investigation, "Age Effects in Coding Tasks: Componential Analysis and Test of the Sensory Deficit Hypothesis." Findings from the experiments are reported in the April issue of the American Psychological Association's journal, Psychology and Aging. Other investigators from Case are Ruth A. Spinks and Cecil W. Thomas.
"Even subtle deficits, such as a reduction in spatial contrast sensitivity, can impair performance on intelligence tests," concludes Gilmore.
Perception deficits gradually appear over the life span of individuals and seem to reach problem levels in older adults and can greatly impact functions in people with dementia or other cognitive-impaired conditions.
The researchers conducted two coding experiments in Case's Perception Lab in the psychology department in the College of Arts and Sciences.
In the first experiment, the researchers tested a group of 30 normal college students of approximately 20 years old and 30 older adults with an average age of 70 years for their ability to encode, remember and search for visual symbols. Each group was given a series of symbol-digit substitution tests, much like an alphabet code that corresponds to a number (example: A is 1, and B is 2). Instead of letters, numbers were matched to a mixture of geometric forms, lines and diagonals in very simple to more complicated symbols.
In the second test, again 60 individuals, all college students of approximately 20 years old, were tested using the symbol-digit test. Half of the group, or 30 students, received a test that used a digital filter in the printing to degrade it to simulate how an older adult with a perception deficit would view the test.
The lab situation controlled for lighting and other environmental factors that might skew the test results.
Similarities in performance were found in the normal college students in both experiments and between the college students taking the test with simulated perception deficits and the older adults.
In the first experiment, the college students performed 34% faster than the adults, making it clear that motor speed can be a major contributor to the age difference in general level of performance, reported the researchers.
The greatest difference was seen on the coding of the simpler symbols that contained diagonal features. Yet on the complex symbols each group was closely matched.
"The poorer performance by older adults may be characterized by a loss of efficiency in visual search," stated the researcher.
In the second experiment, they tested this hypothesis. Again the normal college student group compared to the first experimental group and the degraded test-taking students performed like the older adults.
"The simulation of the age-related sensory deficit markedly reduced the number of items that could be completed in the coding task. This finding offers direct support for the hypothesis that sensory deficits influence coding task performances," stated the researchers.
The testing of this method offers researchers a new way to test for visual information processing deficits and leads to the understanding that visual spatial deficits can impact memory, said the researchers.
The Case Perception Lab has conducted research over the past 25 years on spatial and contrast perceptions. Research from the lab has found a number of links between perception problems and the ability to function normally from reading, writing and moving around the environment.
One of their major findings is that people with dementia can better and more safely navigate their environments when there is a higher contrast between furniture, floors and walls. Adults with dementia also increase the amount of food eaten when the tableware is in high contrast to the table (example a white plate on a dark wood table).
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