Orangutans (Pongo abelii) make flexible decisions relative to reward quality and tool functionality in a multi-dimensional tool-use task

• Published in: PloS one Vol. 14; no. 2; p. e0211031
• Main Authors: Laumer, Isabelle B., Auersperg, Alice M. I., Bugnyar, Thomas, Call, Josep
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 13.02.2019; Public Library of Science (PLoS)
• Subjects: Accessibility; Analysis; Animal behavior; Animal cognition; Animal tool use; Animals; Behavior; Biology; Biology and Life Sciences; Decision making; Decisions; Delay Discounting - physiology; Experimental psychology; Female; Food; Food quality; Foraging (Animal feeding behavior); Foraging behavior; Fruits; Male; Medicine and Health Sciences; Methods; Models, Biological; Monkeys & apes; Motivation - physiology; Orangutans; Pongo - physiology; Pongo abelii; Reinforcement; Reward; Social Sciences; Sumatran orangutan; Tool use; Tool Use Behavior; New York; Austria; United Kingdom > UK; United States > US
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0211031

Making economic decisions in a natural foraging situation that involves the use of tools may require an animal to consider more levels of relational complexity than merely deciding between an immediate and a delayed food option. We used the same method previously used with Goffin´s cockatoos to investigate the orangutans' flexibility for making the most profitable decisions when confronted with five different settings that included one or two different apparatuses, two different tools and two food items (one more preferred than the other). We found that orangutans made profitable decisions relative to reward quality, when the task required the subjects to select a tool over an immediately accessible food reward. Furthermore, most subjects were sensitive to work-effort when the immediate and the delayed option (directly accessible by using a tool) led to the same outcome. Most subjects continued to make profitable decisions that required taking into account the tool functionality. In a final multidimensional task design in which subjects had to simultaneously focus on two apparatuses, two reward qualities and two different tools, the orangutans chose the functional tool to access the high quality reward.