[Self-control in older adulthood: a German version of the delay discounting test by Kirby]

Delay discounting procedures are used to assess self-control vs. impulsivity on a behavioural level. Such procedures include a presentation of a series of choices between smaller, immediate and larger, delayed rewards. The Delay Discounting Test (DDT) by Kirby is an elegant and relatively short procedure. A German DDT version was evaluated in a sample of 147 older and healthy individuals (60-94 years). The discounting rate is in the magnitude of the American version. Its consistency was very high. The largest correlation to external criteria was found for delay of gratification, but also for activation regulation, order, and impulsivity. Further, the discounting rate correlated with anxiety and negative affect, but not with depression and cognitive functioning. Criterion validity and reliability of the DDT could be confirmed. A comprehensive assessment of self-control or impulsivity should include behavioural measures like the DDT besides self-report measures.