Summary and conclusions

The results of many experiments suggest that time often flies less accurately and more variably for older adults than it does for young adults. This chapter has attempted to organize those results in the context of one of the dominant models of interval timing performance, scalar expectancy theory, and to relate them to general questions of age differences in attention and memory. As described throughout the chapter, the evidence regarding some issues (e.g., divided attention effects) is extensive and clear-cut, but in other cases (e.g., variability measures), there have been few or even conflicting reports, and many questions remain completely open and unexplored.

The discussion here has been centered on scalar expectancy theory and other pacemaker-accumulator information-processing models of interval timing. It remains to be seen how other characterizations of interval timing (e.g., the coincidence detection model discussed by Mattell et al., this volume) will account for age effects. The majority of these models consider both cognitive concepts (e.g., attention and memory) and brain systems (especially cortico-striatal circuits) that are of great interest to cognitive aging research. A continuing convergence of research across interval timing and other domains will be important for understanding not only older adults' performance on interval timing tasks, but also the multitude of changes that occur in cognitive functioning as we age.

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