Tool-use by rats (Rattus norvegicus): tool-choice based on tool features

Abstract

In the present study, we investigated whether rats (Rattus norvegicus) could be trained to use tools in an experimental setting. In Experiment 1, we investigated whether rats became able to choose appropriate hook-shaped tools to obtain food based on the spatial arrangements of the tool and food, similar to tests conducted in non-human primates and birds. With training, the rats were able to choose the appropriate hooks. In Experiments 2 and 3, we conducted transfer tests with novel tools. The rats had to choose between a functional and non-functional rake-shaped tool in these experiments. In Experiment 2, the tools differed from those of Experiment 1 in terms of shape, color, and texture. In Experiment 3, there was a contradiction between the appearance and the functionality of these tools. The rats could obtain the food with a functional rake with a transparent blade but could not obtain food with a non-functional rake with an opaque soft blade. All rats chose the functional over the non-functional rakes in Experiment 2, but none of the rats chose the functional rake in Experiment 3. Thus, the rats were able to choose the functional rakes only when there was no contradiction between the appearance and functionality of the tools. These results suggest that rats understand the spatial and physical relationships between the tool, food, and self when there was no such contradiction.

Tool manipulation by rats (Rattus norvegicus) according to the position of food

“…Thus, it is possible that rats moved their ipsilateral paws more easily than their contralateral paws during training, and they simply transferred their rake-manipulation method from training to the test. No tendency was found at the group level regarding which body part was used to pull tools in a previous study that required rats to choose between two tools 27 , but a tendency at the group level in rats was observed for the first time in the present study. However, this tendency may have been caused by the training procedure; thus, further investigation using different experimental procedures is needed to clarify these results.…”

“…The rats were trained to manipulate the rake in the direction of the reward at Level 3 of rake-manipulation training, and they may have simply manipulated the rake in the direction of the reward in a similar manner by using the position of the reward as a discriminative stimulus in the test. It cannot be concluded from this study which interpretation is correct, and this controversy was not fully settled in a previous study using rats 27 .…”

“…An experimental board (23.9 cm wide × 33.5 cm long), on which the tool and reward were presented, was set in front of the sliding door. Details of the experimental box have been described elsewhere 27 .…”

“…A previous study using common marmosets reported that the subjects usually used their hand contralateral to the position of the reward relative to the tool to manipulate it 21 . A previous study in rats investigated the dominant body parts for tool use 27 . In this study, rats were required to choose the more appropriate of two tools to obtain food beyond their reach in an experimental setting.…”

Recombinação de comportamento em ratos Wistar (Rattus norvegicus) em um novo procedimento de deslocamento de caixa

“…A tarefa de deslocamento da caixa se caracteriza pelo uso da caixa como uma ferramenta para alcançar um objetivo (Shumaker, Wakeup & Beck, 2011). Ratos podem aprender a usar ferramentas quando treinados para isso (Nagano & Aoyama, 2016), assim como pombos (Epstein & Medalie, 1983). O uso de ferramentas permite que esses animais de laboratório possam executar resoluções de problemas complexos, e facilita a comparação com outras espécies.…”