The average parameters of the Base and MP models for Experiment 1. The first four conditions are identified by their ITI, with the first and second exposure to the 40s ITI noted parenthetically. The same Weibull parameters, c and α, were used for both models. In the last condition, the probability of hopper activation on a trial was reduced from .1 to .05, with ITI = 40. The error bars delimit the SEM.