A touchscreen study showed that mice could sustain repeated effortful responding and that amphetamine increased progressive-ratio performance. It also highlighted why motivation should be evaluated before a change is attributed solely to cognition.
The researchers adapted progressive-ratio and effort-related-choice procedures for male mice using the same touchscreen apparatus employed in cognitive experiments. Progressive-ratio requirements increased the work needed for reward, while the choice task offered an earned preferred reward against a freely available alternative. Intraperitoneal dopaminergic drugs tested the procedures’ sensitivity.
Amphetamine increased progressive-ratio performance, while selected receptor antagonists reduced it. Raising the work requirement in the choice task shifted behavior toward the freely available alternative. The apparatus therefore supported more than one motivational assessment. However, drug-related changes in willingness to respond are not identical to improved memory, attention or rule learning, even when all tasks use a touchscreen.
Performance can depend on reward value, motor output and response cost as well as the cognitive ability under investigation. A drug that changes one of these factors can change a cognitive-task score without selectively improving its intended construct. The study validated procedures in mice, not a clinical motivation scale or a human treatment dose. It also did not establish that increased breakpoint is always beneficial. Its practical contribution to research design is to measure plausible motivational confounds in the same testing environment, rather than assuming that every change in rewarded behavior represents cognitive enhancement.
See effort behavior dissociating from an EEG marker.