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Reward modulation of cognitive function: aging
p = 0.693). Together, these results suggest that more cautious responding during practice (i.e.
when determining the response deadlines) can explain the higher earnings in the older group
during the test, but that it does not explain the differential task-related effects observed during
the test.
Discussion
The ability to take into account information about potential rewards is crucial for flexible,
adaptive behavior. Increasing age is associated with cognitive decline, yet the psychological
mechanisms underlying this decline remain uncharted. In the current study, we investigated
whether reward motivational deficits underlie age-related changes in flexible cognitive
control across the life span. To this end, we investigated age-related changes in the effect of
reward motivation on flexible cognitive control in 118 participants with age ranging from 14
to 69. We observed overall age-related slowing and an age-related increase in accuracy across
conditions. With increasing age, participants adopted an overall slower but more accurate
strategy. However, whereas younger participants adapted their speed-accuracy strategy to the
trial type, aging was accompanied by a more rigid strategy across trial types. Specifically, on
the more demanding switch trials, younger participants exhibited a reward-related increase
in speed over accuracy, while exhibiting a reward-related decrease in speed over accuracy on
the less demanding repeat trials. By contrast, such reward- and task-dependent adaptation of
speed-accuracy strategy was absent in older participants.
The between subject analysis (
figure 5.3b
) confirmed that younger participants modulate
their behavior differentially in distinct cognitive conditions. By contrast, in the older group,
behavior on the switch trials was indistinguishable from behavior on repeat trials. Thus, with
increasing age, participants drifted towards a more uniform strategy, where they preferred
accuracy over speed across the task as a whole, but failed to adapt their behavior to changing
motivational and cognitive task demands. This is generally in line with a diffusion modeling
study by Starns and Ratcliff (2010), showing that older - in contrast to younger - adults do
not adapt their speed-accuracy strategy to feedback on simple discrimination tasks. Together
these results suggest that alterations in reward-based processing underlie cognitive changes
in aging.
Previous work has suggested that aging is accompanied by deficits in task switching (Kray
et al., 2002). In keeping with this prior work, we observed an age-related increase in the RT
switch cost. Also, a number of studies have demonstrated an age-related decrease in reward
processing (Schott et al., 2007; Rademacher et al., 2014), although some studies have revealed
intact processing of cues predicting an upcoming reward in older individuals (Samanez-
Larkin et al., 2007) (Dreher et al., 2008). The present data – showing an age-related decrease
in the reward effect as well as in the effects of reward on cognitive control (in terms of SAT) –
provide support for the first account. In addition to observing commonly reported age-related
changes in task-switching and reward processing, the current results suggest that aging is also