 The complexity of the task can be adjusted by varying either or both of two parameters: 1 the number of response positions present e.g., number of buttons present, and 2 the number of responses in the sequence required for reinforcement. For example, ten buttons could be present but the participant is only required to press one particular button out of the ten in order to get reinforcement, versus pressing a sequence of ten which involves each button once, versus having only two buttons present, etc. The standard degree of complexity in behavioral pharmacology research is having four response options present and requiring the participant to respond to all four in a particular order to earn reinforcement. 