Fig. 2. Illustration of how arousal changes from trial to trial according to the Arousal-Mediated Learning Model. The grey area is arousal (A); light grey is arousal during the trial, when the CS is present (note the simplifying assumption that A is constant during trials); dark grey is arousal during the ITI. At the end of trial t, the US increases A by a proportion αA of its distance to 1. By the beginning of trial t + 1, A has declined by a proportion βA of its distance to zero (to make the decline in A visible in this illustration, the value of βA was inflated almost 10-fold from empirical estimates). There is no US at the end of trial t + 1, and therefore no increase in A. In the subsequent ITI, A declines at the same rate as in the previous ITI.