Delay discounting: Pigeon, rat, human--does it matter?

Area of Science:

• Behavioral Economics
• Comparative Psychology
• Neuroscience

Background:

• Delay discounting describes the reduced subjective value of outcomes with increasing time delays.
• This phenomenon is observed across species and is often modeled using hyperboloid functions.
• Understanding delay discounting is crucial for comprehending intertemporal choice behavior.

Purpose of the Study:

• To compare delay discounting models and assessment methods in nonhuman animals.
• To review factors influencing delay discounting of rewards in nonhuman animals.
• To evaluate potential species differences in delay discounting between humans and nonhuman animals from an adaptationist viewpoint.

Main Methods:

• Review and synthesis of existing literature on delay discounting in nonhuman animals.
• Comparison of various mathematical models used to describe discounting behavior.
• Analysis of experimental procedures for assessing delay discounting in comparative studies.

Main Results:

• Delay discounting in nonhuman animals is well-described by hyperboloid functions.
• Several variables significantly affect the degree of discounting for delayed reinforcers.
• Potential species differences exist, particularly concerning the timescale of discounting and magnitude effects.

Conclusions:

• Delay discounting is a pervasive process fundamental to decision-making across species.
• Similarities and differences in discounting behavior suggest both conserved and potentially divergent evolutionary adaptations in intertemporal choice.
• Further research is needed to fully elucidate the adaptive significance and species-specific mechanisms of delay discounting.