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

Profiles of animal consciousness: A species-sensitive, two-tier account to quality and distribution

The science of animal consciousness investigates (i) which animal species are conscious (the distribution question) and (ii) how conscious experience differs in detail between species (the quality question). We propose a framework which clearly distinguishes both questions and tackles both of them. This two-tier account distinguishes consciousness along ten dimensions and suggests cognitive capacities which serve as distinct operationalizations for each dimension. The two-tier account achieves three valuable aims: First, it separates strong and weak indicators of the presence of consciousness. Second, these indicators include not only different specific contents but also differences in the way particular contents are processed (by processes of learning, reasoning or abstraction). Third, evidence of consciousness from each dimension can be combined to derive the distinctive multi-dimensional consciousness profile of various species. Thus, the two-tier account shows how the kind of conscious experience of different species can be systematically compared.

Training of Motion Control May Not Improve Tool-Manipulation Ability in Rats (Rattus norvegicus)

In recent times, previous studies have reported the manipulation of tools by rats and degus in controlled experimental settings. However, a previous study reported that only one out of eight experimentally naïve rats could manipulate a rake-shaped tool according to the position of a food reward without prior experience of obtaining the reward with the tool before the test. The present study aimed to improve the training of rats and investigate rodents’ ability to manipulate tools according to food position. Stricter criteria were employed when training the rats to promote the rats’ monitoring of their own tool manipulation. Additional training was introduced to give them the opportunity to learn that the reward moved closer to them by pulling an object connected to the reward. The present study showed that only one of eight rats could manipulate a tool according to the position of the reward without prior experience of obtaining the reward with the tool or perceiving that part of the tool came in contact with the reward, as the previous study showed. The change in training did not enhance the rats’ tool-manipulation ability according to the food position. These procedures should be conducted in a wider variety of animals to investigate whether the training in motion control can promote the subjects’ effective tool-use behavior.

Development of a control task for clarifying the neural mechanisms underlying tool-use behavior in rats (Rattus norvegicus)

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Hook-choice training without tool-use-specific factors can be performed as a control task.

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Prior tool-use training improved rats’ performance in experimental tests.

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Control task for rodents allows investigation of the neural mechanisms of tool-use.

Many studies on non-human animals have attempted to investigate the neural mechanisms underlying tool-use behavior. However, previous studies showed considerable non-tool-use-specific differences between tool-use and control tasks. The purpose of the present study was to develop a control training task for studies that investigate the neural mechanisms behind tool-use in rodents. Eight rats were subjected to control tasks which excluded tool-use-specific factors and consisted of training for hook-pulling and hook-choice tasks, as well as tool-choice tests which included tool-use specific factors and were similar to those in a previous study on rats. With the exception of one rat, the results of the hook-choice training showed that the previous study and the present study had similar difficulty levels. In the tool-choice tests of the present study, rats did not choose the functional tools over the non-functional tools when there was no contradiction between their appearance and functionality, which contrasted with the previous study on which this study was based on. These results suggest that the training task that excludes tool-use-specific factors can be appropriately utilized as a control task for studies investigating the neural mechanisms behind tool-use in animals and, potentially, in humans.

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Hook-choice training without tool-use-specific factors can be performed as a control task.

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Prior tool-use training improved rats’ performance in experimental tests.

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Control task for rodents allows investigation of the neural mechanisms of tool-use.

Rats' (Rattus norvegicus) tool manipulation ability exceeds simple patterned behavior

Many studies have attempted to shed light on the ability of non-human animals to understand physical causality by investigating their tool-use behavior. This study aimed to develop a tool-manipulation task for rodents in which the subjects could not manipulate the tool in the direction of the reward by simple patterned behavior. Eight rats had to use a rake-shaped tool to obtain a food reward placed beyond their reach. During the training, the rats never moved the rakes laterally to obtain the reward. However, in the positional discrimination test, the rake was placed at the center of the experimental apparatus, and the reward was positioned on either the left or right side of the rake. Interestingly, this test indicated that some rats were able to manipulate the rake toward the reward without relying on a patterned behavior acquired during the training. These results suggested that rats have the primitive ability to understand causal relationships in the physical environment. The findings indicate that rats can potentially serve as an animal model to investigate the mechanisms of evolution and development of the understanding of physical causality in humans.

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

Tool-use behaviour has been observed in nonhuman animals in the wild and in experimental settings. In the present study, we investigated whether rats (Rattus norvegicus) could manipulate a tool according to the position of food to obtain the food in an experimental setting. Eight rats were trained to use a rake-shaped tool to obtain food beyond their reach using a step-by-step protocol in the initial training period. Following training, the rake was placed at the centre of the experimental apparatus, and food was placed on either the left or right side of the rake. Rats learned to manipulate the rake to obtain food in situations in which they could not obtain the food just by pulling the rake perpendicularly to themselves. Our findings thus indicate that the rat is a potential animal model to investigate the behavioural and neural mechanisms of tool-use behaviour.