How do goats “read” 2D-images of familiar and unfamiliar conspecifics?

Abstract

To study individual recognition in animals, discrimination tasks are often conducted by presenting 2D images of real conspecifics. However, animals may discriminate the images merely as visual stimulus combinations without establishing referential relationships to the individuals depicted. In the current study, we investigated whether goats are able to discriminate photos of familiar and unfamiliar conspecifics, whether they not only process the photos as visual stimuli, but also understand them as virtual copies of real conspecifics and whether they grasp the concept of familiarity. Using a computer-controlled learning device, in three tests, goats of two experimental groups (A and B) had to discriminate portrait (Te1), profile (Te2) or headless body photos (Te3) of conspecifics. Tests were presented as 4-choice tasks, with one photo from Group A (rewarded) plus three photos from Group B (distractors). That is, the rewarded photo was familiar to Group A, but unfamiliar to Group B. Finally, in a reversal test (Te4) we reversed this principle. The goats learned the discriminations in Te1 to Te3 within two (Te1 and Te2) and three training days (Te3), respectively, and they needed between 91 [CL (66, 126)] and 174 [CL (126, 241)] trials to reach the learning criterion, with no statistically significant differences between the groups. In Te4, in contrast, the animals took 403 [Group A; CL (291, 557)] and 385 [Group B; CL (286, 519)] trials, respectively, to learn the task. The lack of spontaneous preferences for the photo of the familiar conspecific in the pretests of Te1 to Te3 in Group A, as well as the lack of differences in the number of trials to learn the discriminations between both groups, do not at first glance suggest that the goats established a correspondence between real conspecifics and their 2D representations. However, the higher number of trials in Te4 suggests that both groups formed the learning rule of choosing either the known (Group A) or the unknown goat (Group B) over the course of Te1 to Te3 and then failed after the rule was reversed, providing evidence that goats can associate 2D photos of conspecifics with real animals.

Goats who stare at video screens – assessing behavioural responses of goats towards images of familiar and unfamiliar con- and heterospecifics

“…However, their response did not differ between familiar and unfamiliar individuals (irrespective of species), suggesting that goats either cannot spontaneously assign social recognition categories to 2D images or were equally motivated to pay close attention to both categories (but for different reasons). These findings are partly in contrast to related research on goats and other domestic ungulate species (Coulon et al, 2011;Langbein et al, 2023) and thus raise questions about the comparability of test designs.…”

“…In contrast to this, results from other ruminants, such as cattle (Coulon et al, 2011) and sheep (Peirce et al, 2000(Peirce et al, , 2001, have shown that a set of ruminant species have the capability to form this concept using two-dimensional head cues in a visual discrimination task. Langbein et al (2023) also found some evidence that goats are able to associate two-dimensional representations of conspecifics with real animals in a visual discrimination task. It is therefore surprising to see that the subjects in our study did not show differential looking behaviour with respect to the familiarity of the individuals presented.…”

“…Two groups of non-lactating female, one to two years old, Nigerian dwarf goats (group A: 6 subjects, mean age ± SD: 688.2 ± 5.2 d at the start of testing; group B: 6 subjects, 472.2 ± 1.2 d at the start of testing) reared at the Research Institute for Farm Animal Biology (FBN) in Dummerstorf participated in the experiment. The animals had previously participated in an experiment with an automated learning device (Langbein et al, 2023) at an earlier age (groups A and B) and in an experiment on prosocial behaviour in goats (unpublished data; group A). Each group was housed in an 7 approximately 15 m 2 (4.8 m x 3.1 m) pen consisting of a deep-bedded straw area (3.1 m x 3.1 m) and a 0.5 m elevated feeding area (3.1 m x 1.5 m).…”

“…Categorising individuals can simplify decision-making in complex social environments by reducing the information load (Ghirlanda & Enquist, 2003;Langbein et al, 2023;Lombardi, 2008;Zayan & Vauclair, 1998). Therefore, social recognition might be considered a cognitive shortcut for decision-making.…”