Conditional valuation for combinations of goods in primates

Abstract

Valuing goods and selecting the one with the highest value forms the basis of adaptive behaviour across species. While it is obvious that the valuation of a given type of goods depends on ownership and availability of that type of goods, the effects of other goods on valuation of the original good are sometimes underappreciated. Yet, goods interact with each other, indicating that the valuation of a given good is conditional on the other goods it is combined with, both in the wild and the laboratory. Here, we introduce conditional valuation in the context of valuing multiple goods and briefly review how human and animal experimentalists can leverage economic tools for the study of interactions among goods. We then review evidence for conditional valuation for combined foods in both human and non-human primates. In the laboratory, non-human primates show increased valuation of certain combinations of foods but decreased valuation of other types of combinations. Thus, similarly to humans, monkeys appear to value combinations of goods in a conditional fashion. Additionally, both humans and monkeys appear to employ similar neural substrates for the valuation of single goods, such as the orbitofrontal cortex. Together, investigations of our evolutionary precursors may provide insights on how we value interacting goods. This article is part of the theme issue 'Existence and prevalence of economic behaviours among non-human primates'.

Keywords: decision making; joint consumption; valuation.

Figure 1.

An example of two indifference curves. Each indifference curve connects all (equally-desirable) combinations of goods. Thus, the three red dots (one orange and four apples, two oranges and two apples, and four oranges and one apple) represent three equally desirable combinations. Bold blue lines reflect the slopes of the indifference curve and capture diminishing marginal rate of substitution. (Online version in colour.)

Figure 2.

Indifference curves vary for different types of goods. (a) Example indifference curves for perfect complements (left and right shoes of the same style and size); wearing only one shoe is of no use for individuals with two feet. (b) Example indifference curves for perfect substitutes (blue pens and black pens when colour does not matter); these goods are traded at a constant exchange rate, regardless of the amounts of goods on offer. (c) Example of non-convex indifference curve. Combined consumption reduces the utility of olives and chocolate. Thus, for combinations to reach the same utility as separate consumption requires additional olives and chocolates. (d) Example indifference curve with positive slope. The more of a negatively valued good people have to endure, the more of a positively valued good they require as compensation.