Article

Individual differences, aging, and IQ in two-choice tasks

Department of Psychology, The Ohio State University, Columbus, OH 43210, United States.
Cognitive Psychology (Impact Factor: 5.06). 12/2009; 60(3):127-57. DOI: 10.1016/j.cogpsych.2009.09.001
Source: PubMed

ABSTRACT

The effects of aging and IQ on performance were examined in three two-choice tasks: numerosity discrimination, recognition memory, and lexical decision. The experimental data, accuracy, correct and error response times, and response time distributions, were well explained by Ratcliff's (1978) diffusion model. The components of processing identified by the model were compared across levels of IQ (ranging from 83 to 146) and age (college students, 60-74, and 75-90 year olds). Declines in performance with age were not significantly different for low compared to high IQ subjects. IQ but not age had large effects on the quality of the evidence that was obtained from a stimulus or memory, that is, the evidence upon which decisions were based. Applying the model to individual subjects, the components of processing identified by the model for individuals correlated across tasks. In addition, the model's predictions and the data were examined for the "worst performance rule", the finding that age and IQ have larger effects on slower responses than faster responses.

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Available from: Anjali Thapar, Feb 05, 2015
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    • "The importance of this separation is illustrated by applications of the diffusion model in aging research. Ratcliff et al. (2001, 2003), Ratcliff, Gomez et al. (2004), Ratcliff, Thapar, and McKoon (2007, 2010, 2011) have found that the usual aging effect – slower responses for older adults – often comes about not because the quality of the information they obtain from stimuli is less (i.e., not because their drift rates are lower) but instead because their nondecision component is slower and because they set more conservative boundaries, requiring more information to be accumulated before executing a response (e.g., Starns & Ratcliff, 2010). Thus, the frequently stated conclusion that older adults' cognitive processes are, overall, worse than young adults' because all cognitive processes are slowed is incorrect. "
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    • "Average data, often accounting for a non-accurate representation of the individual subjects, have been used in the RDM fitting quite successfully. Specifically, in more than a dozen large studies with 30 to 40 subjects per group, all parameter values obtained from fitting the model to data averaged over subjects were found close (within 1 or 2 SD of each other) to the parameter values obtained from averaging the parameters resulting from fits of the model to the data from individual subjects [51] [52] [53]. "
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    • "Today however, many researchers agree that elderly people slow down, at least in part, because they choose to be more cautious than young people. This means that elderly participants often choose to collect more evidence before they are willing to commit to a decision, a strategy that may result in a substantial loss of speed in return for a small gain in accuracy (Salthouse, 1979; Starns & Ratcliff, 2010; Strayer, Wickens, & Braune, 1987; Ratcliff, This research was supported by Veni and Vidi grants from the Dutch Organization for Scientific Research (NWO). We thank Roger Ratcliff for providing us with the data that are analyzed in Experiment 2. "
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