text: where a is the slope, log b is the intercept, and the logged response ratio and logged reinforcer ratios are the dependent and independent variables, respectively. This straight line is different from the line described by Equation 2 in that its slope and intercept can vary; perfect matching specifies a slope of 1 and an intercept of 0. Because the logarithmic form of the generalized matching equation is a straight line, one can evaluate the equation’s descriptive accuracy by fitting a line to the data. Bias is indicated by the intercept of the straight line, log b, and sensitivity is indicated by the slope of the line, a. One example of a line described by Equation 5 is shown in Figure 10.4. First, note that the slope is less than 1.0. This means that for every unit change in the reinforcer ratio, there is less than a one-unit change in the response ratio. Considering what the value of the slope means in terms of unit changes in the dependent and independent variables is often useful. Second, note that the line is elevated above the origin, which shows some bias for the response alternative in the numerator, which is R1, or the left key, in our example. Of course, the line could be steeper than 1.0, and it could intersect the ordinate below the origin. Consider what this