Computerized intertemporal choice task in chimpanzees (Pan troglodytes) with/without postreward delay

Area of Science:

• Cognitive psychology
• Animal behavior
• Neuroscience

Background:

• Intertemporal choice (ITC) tasks involve choosing between immediate smaller rewards and delayed larger rewards.
• Post-reward delays (PRDs) are used to equalize trial durations but can complicate choice contingencies.
• Chimpanzees exhibit strong self-control in ITC tasks, but their response to PRDs is not well understood.

Purpose of the Study:

• To investigate chimpanzee intertemporal preferences when trial duration is equated by PRDs versus when PRDs are absent.
• To explore the impact of PRDs on chimpanzees' decision-making in ITC tasks using a controlled touchscreen environment.

Main Methods:

• Touchscreen experiments were employed to precisely control delay durations and minimize experimenter interaction.
• Symbolic cues were used for reward options to reduce the influence of visible food rewards.
• Chimpanzees' choices between immediate smaller and delayed larger rewards were recorded under conditions with and without PRDs.

Main Results:

• When trial duration was equated by PRDs, chimpanzees preferred larger rewards but opted for smaller, sooner rewards more frequently with smaller reward amount ratios.
• In the absence of PRDs, two out of four chimpanzees shifted preference to smaller, sooner rewards, improving their overall reward rate, despite methodological limitations.

Conclusions:

• Chimpanzees' intertemporal decision-making is influenced by post-reward delays.
• Further research is needed to fully understand chimpanzee self-control in intertemporal choice tasks involving complex reward contingencies.