# Object Permanence Cognitive Task Solution Using Wild Rodents

## TL;DR

The study found that wood mice and field mice can solve complex object permanence tasks, unlike bank voles, suggesting cognitive differences linked to ecological traits.

## Contribution

This is the first study to test object permanence in wild rodent species, revealing interspecies cognitive and behavioral differences.

## Key findings

- Wood mice and field mice successfully solved complex object permanence tasks.
- Bank voles showed declining success with increasing task difficulty and exhibited immobility.
- Cognitive differences may be linked to ecological specialization and behavioral traits.

## Abstract

Animals from three wild rodent species abundant in mid-Russia biotopes (common Eurasian vole, field mouse and wood mouse) were tested in their ability to operate the object permanence rule (the object perceived previously still exists, although hidden, and could be found). Wood and field mice were able to solve the most difficult test trials, while most bank voles were not able to do so. Neuromorphological differences and ecological specialization could determine these differences, although their relative significance requires further investigation.

The understanding of the object permanence rule (the notion that an object that has disappeared from view continues to exist) is an important issue for animal cognition studies. This ability has been tested in laboratory rodents, but no studies have been conducted using wild rodent species. The aim of this study was to compare the ability to use the object permanence rule in three species of wild rodents and to identify plausible interspecific behavioral differences. The wood mouse (Sylvaemus uralensis), the striped field mouse (Apodemus agrarius), and the bank vole (Clethrionomys glareolus) were used as subjects in the puzzle-box, in which an animal is motivated to escape from a brightly lit environment into the darkness. Test stages 2, 3 and 4 required an understanding that the underpass which leads from light into the dark part of a box still exists, although it is not seen any longer. The test difficulty gradually increased: at first, the passage to the dark was unobstructed; then, it was covered with sawdust; and, finally, it was blocked using a cardboard plug. Interspecific differences were found. Wood mice and striped field mice demonstrated consistently high success rates at all stages of the test, including the most difficult one (when the passage was blocked by a plug), indicating a well-developed ability to operate the object permanence rule. In contrast, the proportion of bank voles who solved the test decreased as the test complexity increased. Bank voles were also characterized by prolonged periods of immobility and lower levels of locomotion. The data suggest that interspecies variability in object permanence task solutions is associated not only with different levels of cognitive ability per se - but also with species-specific behavioral traits, which could be linked to the ecological specialization of these species.