A diffusion model analysis of the effects of aging in the flanker task

The diffusion decision model (DDM) has been used to investigate the effects of aging on information processing in simple response time (RT) tasks. These analyses have consistently shown that the age-related slowing of RTs can be accounted for by slower processing speed in sensorimotor systems and more cautious responding. However, previous DDM assessments of aging have ignored conflict tasks (e.g., the flanker task), the dominant paradigm for investigating age-related differences in executive control, as the DDM is unable to combine task-relevant and task-irrelevant stimulus information. Our study used two recently developed extensions of the DDM-the diffusion model for conflict tasks (DMC) and the shrinking spotlight diffusion model (SSP)-to provide the first model-based assessment of age-related differences in a flanker task featuring a manipulation of the spacing between target and flanking letters. Consistent with previous findings, older adults were globally slower than younger adults, and the magnitude of the flanker effect was larger for older than younger adults only when the spacing between the target and flanking letters was small. Fits of the models to data revealed a superiority of the DMC over the SSP. The DMC accounts for experimental findings with a 62-ms slowing of the nondecision component of RT for older compared to younger adults, a more cautious decision criterion, and enhanced processing of the target and flanking letters in the near periphery, suggesting a stronger attentional engagement in the task