The SS x SR Task

The SS x SR Task, or SS x SR Factorial-Combination Task, is a choice reaction time task with two different irrelevant stimulus dimensions, where one has dimensional overlap with the relevant stimulus and the other has dimensional overlap with the response. This allows an examination of both an S-S consistency effect and an irrelevant S-R consistency effect in the same task. In the dimensional overlap taxonomy, it is considered a Type 7 task.

Stoffels and van der Molen (1988) were the first to explore a factorial combination task, by integrating an auditory Simon task with a Flanker task in the same experimental design. Subjects responded to the letter “H” or the letter “S” with a left or right key-press. These targets were presented with either “H” or “S” flankers on both sides, and an auditory tone presented in either the left or the right ear. The flankers could be S-S consistent or S-S inconsistent, while the tone could be either S-R consistent or S-R inconsistent. The S-S and S-R consistency had additive effects: the S-S consistency effect was the same regardless of S-R consistency, and the S-R consistency effect was the same regardless of S-S consistency.

A number of studies have also combined a visual Simon task with the Stroop-like task (Simon & Berbaum, 1990; Kornblum, 1994; Hommel, 1998; Kornblum et al., 1999). In these studies, subjects were told to respond to a stimulus color with a left or right key-press. The stimulus color was presented on the left or the right side of the display, either with a color word super-imposed on a colored rectangle or with the color itself spelling out the color word. Both the position of the color and the color word are irrelevant. Several of these experiments showed additive effects of S-S and S-R consistency.

Factorial Combination Task

These tasks have played an important role in the debate over the locus of the S-S consistency effect in cognitive processing. Specifically, Kornblum et al. (1999) used the computational dimensional overlap model to demonstrate that both the additivity and the different time-courses of S-S and S-R effects can be explained by assuming that stimulus and response processing occur in discrete stages and that S-S and S-R dimensional overlap impact different processing stages.


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