Horses Solve Visible but Not Invisible Displacement Tasks in an Object Permanence Paradigm

Abstract

A key question in the field of animal cognition is how animals comprehend their physical world. Object permanence is one of the fundamental features of physical cognition. It is the ability to reason about hidden objects and to mentally reconstruct their invisible displacements. This cognitive skill has been studied in a wide range of species but never directly in the horse (Equus caballus). In this study, we therefore assessed the understanding of visible and invisible displacements in adult Welsh mares in two complementary experiments, using different horses. In experiment 1, visible displacement was investigated using two tasks adapted from the Uzgiris and Hunt scale 1. Invisible displacement was assessed using a transposition task, in which food was first hidden in one of two containers and the location of the containers was then switched. In experiment 2, we further investigated horses' understanding of visible and invisible displacements using an easier procedure designed to avoid potentially confounding factors. In both experiments, horses successfully completed the tasks involving visible displacement with two or three possible hiding places. However, in both experiments, horses failed the transposition tasks, suggesting that they may not be able to track the displacement of an object that is not directly perceived (i.e., invisible displacement). These results bring new insights into object permanence in horses and how they represent their physical world.

Horses’ (Equus caballus) performance in visible and invisible displacement tasks is expressed in frustration behavior and heart rate

“…The finding that horses were able to solve the visible displacement task but not the invisible one was in accordance with our hypothesis and with previous findings by Troesch and colleagues (18) (Trösch et al 2020). In our study, however, the results were achieved using a larger sample (>30 horses) compared to the study by ( 18) (Trösch et al 2020) (<20 horses).…”

“…The finding that horses were able to solve the visible displacement task but not the invisible one was in accordance with our hypothesis and with previous findings by Troesch and colleagues (18) (Trösch et al 2020). In our study, however, the results were achieved using a larger sample (>30 horses) compared to the study by ( 18) (Trösch et al 2020) (<20 horses). The notion that horses chose consistently the side where they had last seen the target in the invisible displacement task adds further support to the hypothesis that horses are able to remember the location of known object when hidden.…”

“…More sophisticated forms of locating objects e.g., when they are hidden and displaced, have, to the best our knowledge, only been studied by one team. This particular study showed that horses were capable of solving visible displacement of a reward on either two or three possible hiding locations but failed to solve invisible disposition tasks (18) (Trösch et al 2020). The results however need to be reviewed with caution due to the limited sample size (n=16) and as only one sex was included (only females).…”

“…The current study aimed to investigate horses' performance in visible and invisible displacement tasks and investigated whether specific ontogenetic, behavioral and physiological factors were associated with performance. The hypothesis was that horses would be able to solve visible but not invisible displacement tasks following the results from Troesch and colleagues (18). In addition, the study investigated if individual characteristics such as training level, age, sex and coat color (red or other color) influenced horses' performance in the tasks, and if horses who were successful in one task also were successful in another.…”

Horses’ (Equus caballus) Ability to Solve Visible but Not Invisible Displacement Tasks Is Associated With Frustration Behavior and Heart Rate

“…More sophisticated forms of locating objects e.g., when they are hidden and displaced, have, to the best our knowledge, only been studied by one team. This particular study showed that horses were capable of solving visible displacement of a reward on either two or three possible hiding locations but failed to solve invisible disposition tasks ( Trösch et al, 2020 ). The results, however, need to be reviewed with caution due to the limited sample size ( n = 16) and as only one sex was included (only females).…”