Age and Time Effects on Implicit and Explicit Learning

Abstract

Background/Study Context: It has been proposed that effects of aging are more pronounced for explicit than for implicit motor learning. The authors evaluated this claim by comparing the efficacy of explicit and implicit learning of a movement sequence in young and older adults, and by testing the resilience against fatigue and secondary tasking after learning. It was also examined whether explicit learning in older adults can be promoted by alleviating time constraints during learning.

Methods: The alternating serial reaction time task (ASRTT) was used. Experiment 1 compared the benefits of receiving full instructions about the stimulus sequence relative to receiving no instructions in young (20–25 years) and older (50–65 years) adults during retention and during transfer to fatigue and secondary task conditions. Experiment 2 alleviated time constraints during the initial bouts of practice with full instructions.

Results: Experiment 1 indicated that the older adults learned on the ASRTT and achieved similar performance as young adults when no instructions were given. In contrast to the young adults, learning was not superior in older adults who received full instructions compared with those who did not. Experiment 2 indicated that alleviating time constraints allowed some of the older adults to gain from instruction but only under relatively low time constraints, but there was no retention with rigorous time constraints.

Conclusion: Explicit learning, but not implicit learning, declines in older adults. This is partly due to older adults difficulties to apply explicit knowledge. Less rigorous time constraints can help to ameliorate some of these difficulties and may induce levels of explicit learning in older adults that will result in superior performance compared with implicit learning. Implicit learning did occur under time constraints that prevented explicit learning.

Notes

1. ¹There is a growing body of motor learning literature that in fact reveals greater robustness against dual tasking being conveyed after implicit learning compared with explicit learning (Chauvel et al., 2012). Possibly these discrepant findings are related to differences in task constraints. Rather than externally paced timing tasks as the SRTT; these studies mostly adopted self-paced far-aiming tasks such as golf putting and ball throwing.

2. ²Obviously, triplets occur much less frequently than individual ordered and random stimuli (i.e., triplets consist of combinations of individual stimuli). Therefore, their occurrence is too infrequent to reliably analyze them over blocks of 80 trials (as in the retention test). Hence, we analyzed triplets by combining 5 blocks of practice (i.e., an epoch).

3. ³Submitting the response time to 2 (age) × 2 (instruction) × 10 (epoch) × 3 (triplet) analysis of variance with repeated measures on the last two factors revealed a significant age by instruction by triplet interaction, F(2, 68) = 9.3, p < .005, η_p² = 0.21. Post hoc indicated that for each of the four groups, response times were significantly larger for random inconsistent triplets than random consistent and patterned triplets. Response times for the random consistent triplets only differed from the patterned triplets in the young instruction group, with the patterned triplets having shorter response times.

4. ⁴The comparison between the transfer to secondary task condition and the second retention test revealed an identical pattern of results. We only report the contrast between the transfer to secondary task condition and the preceding first retention test, because this allows for a direct comparison with Experiment 1.