Proefschrift_Holstein

Chapter 5

A

B

Reward e ect on task switching

p < 0.001 Reward e ect on task switching

study

A C D

p < 0.001

p > 0.05

< 26 > 25

age group

2

r = - 0.360, p = 0.003 *

0.2

1

more speed on

high reward trials

0

(SAT)

0

(SAT)

-0.2

Younger Older

-1

high reward - low reward N = 35

- low (switch - repeat)

high (switch - repeat)

N = 33

10 20 30 40 50 60 70

Age (years)

Age group

higher accuracy on high reward trials

Figure 5.3 The effect of Reward on Task switching diminishes with age in a subgroup matched for maximum available reward The results in figure 2 were supported by an additional analysis, in which we only included the participants who all received the exact same version of the task (study A, C, D in table 1). A: This analysis confirmed that the effect of Reward on Task switching is reduced with age. The outline of the data points indicates the study in which each participant participated (table 1).The red and blue data points refer to the younger and older group in a subsequent median split analysis (B), * The black solid line indicates the regression slope (Pearson) for the subgroup (N = 68), the Spearman correlation is reported. B: Analysis with age as a between subject factor (median split) revealed significant effects of Reward on Task switching in the younger group, but not the older group. also reflect these age-related differences in the maximum time participants had to respond on each trial type. However, this age-related effect in response deadlines was not different for repeat and switch trials (Age x Task switching in terms of response deadline: r (ρ) = 0.050, p = 0.588). Next, we assessed whether the difference between the average response times during the actual test and the average response times during the practice (i.e. average response deadlines) changed with age. Indeed, this difference increased with age (Age x Response time difference: r (ρ) = 0.467, p < 0.001), suggesting that the average response deadline was less close to their maximum speed for older than younger participants. To test whether this can account for the higher earnings, we assessed whether the response time difference was associated with the total earnings. Indeed, a larger response deadline difference (i.e. increased room for improvement on test compared with practice) was associated with higher earnings (Total earnings x Response time difference: r (ρ) = 0.480, p < 0.001). Crucially however, the difference in response times between practice and test was not associated with the task effects (Rewarded Task switching effects in terms of SAT x Response time difference (r (ρ) = -0.037,

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