A flexible body image is required by animals if they are to adapt to body changes and move effectively within a structurally complex environment. Here, we show that terrestrial hermit crabs, Coenobita rugosus , which frequently change shells, can modify walking behaviour, dependent on the shape of the shell. Hermit crabs walked along a corridor that had alternating left and right corners; if it was narrow at the corner, crabs rotated their bodies to avoid the wall, indicating an awareness of environmental obstacles. This rotation increased when a plastic plate was attached to the shell. We suggest that the shell, when extended by the plate, becomes assimilated to the hermit crab's own body. While there are cases of a tool being assimilated with the body, our result is the first example of the habitat where an animal lives and/or carries being part of a virtual body.

Insects use a navigational toolkit consisting of multiple strategies such as path integration, view-dependent recognition methods and olfactory cues. The question arises as to how directional cues afforded by a visual panorama combine with olfactory cues from a pheromone trail to guide ants towards their nest. We positioned a garden antLasius nigeron a rotating table, whereon a segment of a pheromone trail relative to the stationary panorama was rotated while the ant walked along the trail towards its nest. The rotational speed of the table (3 r.p.m.) was set so that the table would rotate through about 90° by the time that an ant had walked from the start to the centre of the table. The ant completed a U-turn at about this point and so travelled in a nest-ward direction without leaving the trail. These results suggest that the ants persist on the pheromone trail and use visual input to determine their direction of travel along the trail.

How is our bodily self-consciousness acquired, and how does it affect cognition? To investigate this, we conducted an experiment using the squeeze machine, a device that provides pressure along the length of the user’s whole body. The squeeze machine is used to help autistic people relax. The inventor of the machine, Dr. Temple Grandin says that the squeeze machine, beyond bringing her relaxation, enables her to feel empathy for others. This claim is of considerable interest and raises the following two points; first, the problem of empathy in autism is an important issue and Squeeze Machine could be effective. Second, it suggests that the physical action of Squeeze Machine could provide an insight of mind-body problem to us. Here, we hypothesize that the squeeze machine focuses conscious to direct the bodily self, transforming bodily self-consciousness itself. Such intentionality could bring empathy to others. In this study, we tested whether bodily self-consciousness would be transformed through the squeeze-machine experience. In the first part of the protocol, we simplified the original design of Grandin’s squeeze machine but ensured that it retained its relaxing effect. In the second part of the protocol, we adopted a preestablished method of peri-personal space (PPS) measurement to estimate changes in extended bodily space. The results showed that the boundaries of PPS that appeared in the control experiment disappeared during the use of the squeeze machine. Indeed, collected subjective reports suggest that bodily self-consciousness continually drifted between the point of action of the external force (squeeze-machine pressure) and of an internal force (balance among body parts that are usually not consciously controlled), leading to the abandonment of the immobilization of individual PPS.

The feeling that a body part is one’s own body (sense of ownership; SoO) and the feeling based on the causal relationship between one’s will and action (sense of agency; SoA) have been recognized as the basis of our bodily self-consciousness. Previously, the illusory SoO over a fake body part (e.g., rubber hand) was introduced as the rubber hand illusion (RHI). Furthermore, it was determined that one could also evoke a SoA over an object with movements linked to the one’s prior intention. On the other hand, the postdictivity of our spontaneity implies that it is essentially inseparable whether actions originate from self or others. In other words, our SoA or daily experiences are obtained in such as inseparable scenario. Previous research, however, has maintained the premise that self- and other-origin movements are perceptually distinguishable. Here, we implement a protocol to make these aspects ambiguous for the participants and to estimate whether they can feel SoO and/or SoA and how. To this end, we employ an experiment using virtual reality, under which participants observe virtual fingers moving very slowly (or quickly or not moving) while their own fingers do not move. For evaluation of the illusory SoO, measurements of skin conductance responses against a knife threat are adopted. Additionally, we introduce face-to-face interviews to determine whether the feelings regarding the slow movement match the conventional SoA definition. Our representative results suggest that the SoO is evoked over the hand, and various attitudes to accept its movement as the participant’s own with awareness that they did not originate it are reported by the majority. As the results show, the novelty of this protocol is discovering that in such a situation, the SoO cooperates with an externally produced SoA to establish one’s own bodily experience rather than the independence of the SoO and SoA.