Abstract: A Multi-Level Model of Individual Differences in Speed/Accuracy Tradeoff (SATin)

Individuals performing an experimental cognitive task have a choice whether to favor accuracy, speed, or weight them both equally. Models of speed/ accuracy tradeoff have been proposed in the assessment literature ( van der Linden, 2007 ) and experimental literature ( Ratcliff & Rouder, 1998 ). However, these models do not estimate individual differences in choice of speed/ accuracy tradeoff at between- and within-subjects levels. The top of Figure 1 presents the equations and path diagram for the SATin model. Individual differences in speed/ accuracy tradeoff will be modeled at two levels with, 1) variability in Tradeoff (between-subject level, Level 2) and 2) variability in c (within-subject level, Level 1). An individual's Tradeoff factor score represents the individual's distributional position relative to others regarding whether they favor speed (values < 0), accuracy (values > 0), or neither (value = 0). A negative c indicates that the individual is trading off speed and accuracy for these particular trials, whereas a positive and zero c indicate the individual is not trading off. [Figure: see text] Panels 1 and 2 illustrate Simpson's paradox, where speed/ accuracy tradeoff occurs in opposing directions at between- and within-subject levels. This highlights the need for a multi-level model as the researcher would draw opposing conclusions by observing only one of these levels. Simulations studies compared the SATin model to a popular model in cognitive psychology that uses speed alone to estimate ability. SATin outperformed this model by accounting for substantially more variance in actual ability.