What counts for ‘counting’? Chimpanzees, Pan troglodytes, respond appropriately to relevant and irrelevant information in a quantity judgment task

Abstract

Nonhuman animals quantify all manner of things, and the way in which this is done is fairly well understood. However, little research has been conducted to determine how they know what is or is not relevant in the instances in which they quantify stimuli. We assessed how four chimpanzees chose between two sets of food items when the items were distributed across separate spatial arrays. Each item was covered by a container, and then was revealed in sequence so that neither whole set was visible at one time. After all containers were revealed, some were revealed again. The chimpanzees should have ignored items that were seen a second time and instead enumerated each item only once. In another test, some of the items were transposed in location and then uncovered again. Here, the chimpanzees needed to recognize that the newly shown food items were ones they already had seen. Overall, the chimpanzees were successful in selecting the truly larger array of items despite these potential distracting re-presentations of items. Discrimination performance also reflected analogue magnitude estimation because comparisons of sets that differed by larger amounts were easier than comparisons that differed by smaller amounts. Thus, chimpanzee quantity judgments for nonvisible sets of items are inexact, but they include an aspect of control for determining when items are uniquely presented versus re-presented.

Elephants have a nose for quantity

“…As a group, the elephants' performance was worse with an increase in ratio value, better with an increase in ratio disparity, and remained consistent when the magnitude of the quantities increased at the same ratio. Thus, using olfaction, the elephants performed similarly to other species tested with vision and appeared to both make approximations about food quantity and recognize the relative difference between two amounts (44)(45)(46). Prior research suggests that animals are able to cognitively represent quantity through approximation, and thus recognize the relative difference between two amounts rather than the exact quantity each represents (e.g., refs.…”

When less is more: like humans, chimpanzees (Pan troglodytes) misperceive food amounts based on plate size

“…Moreover, the chimpanzees tested in the current study are highly proficient on a wide range of quantity judgment tasks (Beran 2001, 2004, 2012; Beran and Beran 2004; Beran et al 2013; Rumbaugh et al 1987). Beyond their quantitative capacities, chimpanzee choice behavior is likely motivated by maximization of energy intake (Sayers and Menzel 2012).…”

Are great apes able to reason from multi‐item samples to populations of food items?

“…Many species are capable of numerical cognition: For example, great apes [e.g., Beran, McIntyre, Garland, & Evans, ; Boysen & Berntson, ; Call, ; Hanus & Call, ], old‐ and new‐world monkeys [e.g., Barnard et al, ; Beran, Evans, Leighty, Harris, & Rice, ; Beran & Parrish, ], elephants (Perdue, Talbot, Stone, & Beran, ), bears (Vonk & Beran, ), raccoons (Davis, ), dogs (Ward & Smuts, ), cats (Pisa & Agrillo, ), birds [e.g., Rugani, Cavazzana, Vallortigara, & Regolin, ], fish [e.g., Potrich, Sovrano, Stancher, & Vallortigara, ], and even insects [bees: Dacke & Srinivasan, ; ants: Reznikova & Ryabko, ] are able to compare quantities, suggesting that representing numerosity is an evolutionary ancient trait. The practical advantages of such a capacity are obvious: in the context of foraging, for example, comparing quantities is a highly useful tool to identify the most profitable feeding location [see e.g., Farnsworth & Smolinski, and Hunt, Low, & Burns, for field experiments on quantity discrimination in a foraging context].…”