Bias and Sensitivity Parameters and the Matching Law

The "generalized matching law" includes two parameters that can produce systematic deviations from strict matching: bias and sensitivity (Baum, 1974). Bias is a preference for responding on one key over the other, independent of the relative rates of reinforcement associated with those keys. Sensitivity determines whether the relative rate of responding is less sensitive to the relative rate of reinforcement than expected under strict matching (a condition called "undermatching"), as sensitive as needed for strict matching, or more sensitive than expected under strict matching (a condition called "overmatching"). The applet below allows you to experiment with various settings of bias (vertical slider) and sensitivity (horizontal slider). See how well you can match the shape of the curve to the right-hand figure.