摘要：The commentaries appropriately mention boundary conditions for the less is more effect (Beran,
this issue; Carvalho et al., this issue) and the caution that choice behavior that seems suboptimal
in the laboratory may be optimal in nature (Vasconcelos et al., this issue). Pisklak et al. (this issue)
object to my definition of contrast to describe the difference between probability (or magnitude)
of reinforcement expected and obtained but they focus on only one kind of contrast, behavioral
contrast. Carvalho et al. question how impulsivity can account for the failure to choose optimally in
the ephemeral reward task. The justification comes from research on delay discounting (a measure
of impulsivity) in which further delaying both the smaller sooner and the larger later reward can
shift preference in the direction of optimality. The same occurs with the ephemeral reward task.
With regard to the midsession reversal task, Carvalho et al. question our interpretation of the
positive effect on accuracy of reducing the probability of reinforcement for correct choice of S2
(the correct stimulus during the second half of the session). They argue that according to our
attentional account, reducing the probability of reinforcement for correct choice of S1 (the correct
stimulus during the first half of the session) should have a similar effect. However, during that
half of the session, choice of S2 would be an anticipatory error, thus not very helpful as a cue.
Instead, we suggest that any manipulation that shifts attention from S2 to S1 (e.g., increasing the
response requirement to S2) should improve task accuracy and it does. Finally, I suggest that
evolved heuristics may account for an animal’s suboptimal choice but that an animal’s flexibility in
dealing with a changing environment may be a useful ability to have and may be worth studying.
