Der & Deary (2017), aimed to investigate the relationship between intelligence and reaction time (RT). Specifically, the study aimed to investigate how RT and general mental abilities changed with age. The study was specifically designed concerning simple reaction time (SRT) and choice reaction time (CRT). SRT involved measuring the time it took for an individual to react to a single stimulus with a specific response while CRT involved a more complex task where individuals had to choose from multiple possible responses based on different stimuli. Der & Deary (2017) hypothesized that the pattern of correlation between SRT and CRT differed with age. The research questions guiding this study were: i) How strong is the correlation between intelligence and RT parameters? ii) Does the relationship between them vary with age across adulthood? Is the underlying relationship linear?
In this study, the dependent variables (DVs) primarily encompass reaction time (RT) measures, including both simple and 4-choice RT. For each type of RT, the mean and standard deviation were recorded as key outcome variables (Der & Deary, 2017). The independent variables (IVs) involved in the analysis include cognitive abilities assessed through the Alice Heim 4 test of general intelligence (part I), represented by the total number of correct answers (AH4 score). Age cohorts were also a crucial independent variable, as the study’s modeling and analyses were conducted separately for three distinct age groups: individuals around 30 years old, 50 years old, and 69 years old.
The study utilized data from the West of Scotland Twenty-07 study, a longitudinal investigation into socially structured health inequalities. In the fourth wave of data collection (2000/2001), participants (2661) underwent the Alice Heim 4 test of general intelligence (part I) and tasks assessing simple and 4-choice reaction time (RT). RT measures were recorded using a portable device, and the analysis involved Box-Cox transformations for normalizing distributions, polynomial regression to model the RT-IQ relationship, and locally weighted regression for comparison (Der & Deary, 2017). The intra-individual standard deviation (ISD) of RT, addressing variability, was pre-processed using the coefficient of variation and residuals from a mean-dependent regression. Modeling was performed separately for each age cohort, considering non-linear functions. Attrition impact was assessed using inverse probability weights. All analyses were conducted using SAS version 9.3.
The findings by Der & Deary (2017) indicated an increase in correlation between simple and 4-choice reaction time with age. It also revealed negative associations between RT means and cognitive abilities, particularly pronounced for choice RT where people with a faster reaction time tended to have higher cognitive abilities. Descriptive statistics revealed age-related trends in reaction time (RT) means and AH4 scores. Positive skewness and heteroscedasticity were observed in RT measures, impacting the bivariate relationship with IQ. The findings also indicated age-related increases in RT means and intra-individual standard deviation (ISD). On average, reaction time reduced as individuals aged as indicated by a greater variability among older individuals. Polynomial regression and local regression techniques highlighted the complexity of these relationships across different age groups. Scatterplots illustrated negative associations between RT means and AH4 scores, revealing floor effects and decreasing variance.
References
Der, G., & Deary, I. J. (2017). The relationship between intelligence and reaction time varies with age: Results from three representative narrow-age age cohorts at 30, 50 and 69 years. Intelligence, 64, 89-97.
Der, G., & Deary, I. J. (2017). The relationship between intelligence and reaction time varies with age: Results from three representative narrow-age age cohorts at 30, 50 and 69 years. Intelligence, 64, 89-97.
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