 In light of this formulation of the lens model, return to Simon’s remarks concerning the classification of environmental affordance versus behavioral constraint. The conception of the lens model as a linear model is indebted to signal detection theory, which was developed to improve the accuracy of early radar systems. Thus, the model inherits from engineering a clean division between subject and environment. However, suppose for a moment that both the environmental mechanism producing the criterion value and the subject’s predicted response are linear. Now consider the error-term, \(\epsilon_s\). That term may refer to biological constraints that are responses to adaptive pressures on the whole organism. If so, ought \(\epsilon_s\) be classified as an environmental constraint rather than a behavioral constraint? The answer will depend on what follows from the reclassification, which will depend on the model and the goal of inquiry  (section 8).  If we were using the lens model to understand the ecological validity of an organism’s judgment, then reclassifying \(\epsilon_s\) as an environmental constraint would only introduce confusion; If instead our focus was to distinguish between behavior that is subject to choice and behavior that is precluded from choice, then the proposed reclassification may herald clarity—but then we would surely abandon the lens model for something else, or in any case would no longer be referring to the parameter \(\epsilon_s\) in  Figure 2.