“I’ll remember it when I see it”: The impact of vision on
backward digit span in older adults
Megan Duffett, Brittany Faux, Dr. Aimée M. Surprenant
Memorial University of Newfoundland
- Participants and Procedure
- Twenty-five older adults aged 62 to 83 (M = 70.86, SD = 5.89).
- Recruited from St. John’s and surrounding areas
- 56% female sample, with self rated health ranging from average to above average
- Testing took place in two one-hour sessions.
- Completed memory, cognitive, speed, audio and vision tests .
- All participants were compensated for their time.
Amid the presence of an aging population, it is important to examine memory loss in older adults, and revaluate age as the causal factor. Correlational studies have noted a prominent link between memory and vision decline in older adults. One theory suggests that straining resources to meet sensory demands may result in less effort devoted towards memory, and a more abstract representation of stimuli being stored. This would explain why older adults commonly rely on gist based processing. In the present study, older adult participants performed a number of vision tests, and completed multiple cognitive and memory tasks. Participants with poorer vision performed worse on the backwards digit span task than participants with better vision. Furthermore, performance on the backwards digit span was related to performance on free recall memory tasks. Data collection is ongoing.
- General demographics questionnaire.
- Backwards and forwards digit span
- computerized tasks
- Grating Contrast Sensitivity (FACT)
- Landolt C Visual Acuity measure
- Contrast Sensitivity booklet
- Rabin contrast sensitivity test
- Basic audio test
- Speed of information processing measure
- Age-related memory loss is a common occurrence, however, research suggests that age may not be the important causal factor.
- Many studies have documented significant correlations between decreased sensory function and memory abilities in older adults (e.g. Salthouse, et al., 1998; Zekveld, et al., 2007; Anstey et al., 2006; Baltes & Lindenberger, 1997).
- While relationships have been found with a number of sensory functions, vision and hearing typically account for the most variance.
- Three general explanations have attempted to account for these findings: The common cause hypothesis, the speed hypothesis, and the information degradation hypothesis. The present study aimed to examine the third hypothesis.
- The Common Cause Hypothesis
- States that as the body ages, a common cause creates problems in both memory and sensory abilities (e.g. visual acuity, hearing, grip strength, upper leg strength, and blood pressure).
- Declares that sensory deprivation causes longer encoding times when processing stimuli. For example, someone with poor vision may have to strain their eyes when reading, causing longer processing times and less rehearsal.
- The Information Degradation Hypothesis
- States that sensory deficits result in worse input of items and harder discrimination at recall. Accordingly, individuals suffering from hearing or vision deficits should show cognitive declines, compared to a normal population.
Discussion and Conclusion
- Participants were separated into two groups depended on their scores on the backwards digit span (BDS) task, low BDS or high BDS. Groups were determined by a median split of BDS scores. T-tests were conducted to compare vision scores between both BDS groups. The results are presented below:
- Backwards Digit Span (BDS) significantly correlated with free recall memory tasks, while Forward Digit Span (FDS) did not.
- After age was partialled out, BDS continued to significantly correlate with a number of vision tests, while FDS did not.
- While FDS allowed the participants to repeat the number string (e.g., 384, 3845…) BDS did not, instead forcing reliance upon a more abstract representation of the presented numbers.
- According to the information degradation hypothesis, those with perceptual deficits should perform worse in such tasks as the BDS. The findings of the current study lend support to the hypothesis.
- A median split independent t-test revealed that those who performed worse on BDS had lower visual performance on all acuity and contrast sensitivity tasks.
- While the two BDS groups significantly differed according to vision, they did not differ on age.
- The current study’s findings remove age as a causal factor for all memory loss. If age were the main factor, than BDS should not have correlated with the vision tests once age had been controlled for.
- These results support the information degradation hypothesis.
- Contrary to predictions of the speed hypothesis, measures of speed were unrelated to anything once age was partialled out.
- Contrary to the common cause hypothesis, objective hearing scores were unrelated to performance on visual tasks (performance was task specific).
- The results support the information degradation hypothesis, and thus confirm the hypothesis of the study.
- Data collection is ongoing.
- The present study will look to examine how visual ability impacts performance on certain types of cognitive and memory tests in older adults. It is hypothesized that older adults with poor vision will perform substantially worse on memory tests in comparison to those with normal vision.
Note. FACT: Grading contrast sensitivity chart average scores, Rabin Gl: Rabin contrast sensitivity scores with glare, CSVAvg: Contrast sensitivity book average score.
Research supported by: Natural Sciences and Engineering Research Council of Canada– Undergraduate Student Research Award