That dog won't fit: body size awareness in dogs

Cleaner fish with mirror self-recognition capacity precisely realize their body size based on their mental image

Animals exhibiting mirror self-recognition (MSR) are considered self-aware; however, studies on their level of self-awareness remain inconclusive. Recent research has indicated the potential for cleaner fish (Labroides dimidiatus) to possess a sophisticated level of private self-awareness. However, as this study revealed only an aspect of private self-awareness, further investigation into other elements is essential to substantiate this hypothesis. Here, we show that cleaner fish, having attained MSR, construct a mental image of their bodies by investigating their ability to recall body size. A size-based hierarchy governs the outcomes of their confrontations. The mirror-naïve fish behaved aggressively when presented with photographs of two unfamiliar conspecifics that were 10% larger and 10% smaller than their body sizes. After passing the MSR test, they refrained from aggression toward the larger photographs but still behaved aggressively toward the smaller ones without re-examining their mirror images. These findings suggest that cleaner fish accurately recognize their body size based on mental images of their bodies formed through MSR. Additionally, mirror-experienced fish frequently revisited the mirror when presented with an intimidating larger photograph, implying the potential use of mirrors for assessing body size. Our study established cleaner fish as the first non-human animal to be demonstrated to possess private self-awareness.

The Inner Lives of Cephalopods

The minds of cephalopods have captivated scientists for millennia, yet the extent that we can understand their subjective experiences remains contested. In this article, we consider the sum of our scientific progress towards understanding the inner lives of cephalopods. Here, we outline the behavioral responses to specific experimental paradigms that are helping us to reveal their subjective experiences. We consider evidence from three broad research categories, which help to illuminate whether soft-bodied cephalopods (octopus, cuttlefish, and squid) have an awareness of self, awareness of others, and an awareness of time. Where there are current gaps in the literature, we outline cephalopod behaviors that warrant experimental investigation. We argue that investigations, especially framed through the lens of comparative psychology, have the potential to extend our understanding of the inner lives of this extraordinary class of animals.

Body size awareness matters when dogs decide whether to detour an obstacle or opt for a shortcut

Body-awareness is one of the fundamental modules of self-representation. We investigated how body-awareness could contribute to dogs' decision making in a novel spatial problem where multiple solutions are possible. Family dogs (N = 68) had to obtain a treat from behind a transparent fence. They had two options: either detour around the fence (7 m), or take a shortcut through a doorway (2 m). We had three conditions: small door open, large door open, and doors closed. Our results indicated that dogs assess the size of the doorway, and if they find it too small, they decide to detour instead, while in the case of the open large door, they rather opted for the shortcut without hesitation. Shorter headed dogs tended to choose open doors more often, while longer headed dogs rather chose detours, probably because of their better peripheral vision. While body size awareness did not manifest differently in dogs with short or long heads, we showed for the first time a connection between head shape and physical cognition in dogs. We showed that dogs rely on their body-awareness in a naturalistic setting where multiple solutions exist simultaneously. Dogs make decisions without lengthy trial-and-error learning and choose between options based on their body-awareness.

Ferrets (Mustela furo) Are Aware of Their Dimensions

Self-awareness is a complex phenomenon expressed as the ability of an individual to separate "self-entity" from "other entity". One of its earliest evolutionary components is body size awareness, namely, the ability to consider the boundaries of one's own body as factors influencing interaction with surrounding objects. For ferrets, Mustela furo, the task requiring the penetration of various holes is ecologically relevant. We designed an experimental study in which the ferrets were supposed to select one opening out of three to get the bait. The first experiment was aimed at studying whether ferrets would prefer the holes basing on the hole size. In the second experiment, we tested the ferrets' ability to select a single passable hole on the first try while the impassable ones were larger in area. Results from the first experiment show that when choosing from the three passable openings, the animals preferred the shortest path to the bait and ignored the size of the holes. In the second experiment, all tested ferrets preferred to penetrate the passable opening on the first attempt, even though the areas of the two impenetrable ones were larger. We argue that these data indicate that ferrets are aware of their own body size.

Hooded Crows (Corvus cornix) May Be Aware of Their Own Body Size

Body-awareness is one of the manifestations of self-awareness, expressed in the ability of people and animals to represent their own body physical properties. Relatively little work has been devoted to this phenomenon in comparison with the studies of the ability of self-recognition in the mirror, and most studies have been conducted on mammals and human infants. Crows are known to be “clever” birds, so we investigated whether hooded crows (Corvus cornix) may be aware of their own body size. We set up an experimental design in which the crows had to pass through one of three openings to reach the bait. In the first experiment, we studied whether crows prefer a larger hole if all the three are suitable for passage, and what other predictors influence their choice. In the second experiment, we assessed the ability of the crows to select a single passable hole out of three on the first attempt, even though the area of the former was smaller than that of the other two. The results of the first experiment suggest that when choosing among three passable holes, crows prefer those holes that require less effort from them, e.g., they do not need to crouch or make other additional movements. In the second experiment, three of the five crows reliably more often chose a single passable hole on the first try, despite its smaller size. We believe that these results suggest that hooded crows may be aware of their own body size.

Can Dogs Limbo? Dogs' Perception of Affordances for Negotiating an Opening

Simple Summary

Recent behavioral research with domestic dogs has focused largely on their social cognition: how they interact with and interpret both other dogs and humans. Less well studied are the various aspects of their perceptual experience which might provide knowledge of how they understand the non-social world and themselves. In two studies, we look at how dogs navigate their environment. We first set up a situation to test whether dogs understand when they are too big to go through an opening; we also look at how they adjust their bodies to increasingly smaller (shorter) openings. We then also look at how dogs navigate an opening when their body width is effectively increased by their holding a stick in their mouth. We find that dogs show more hesitation approaching openings that are too small than ones through which they comfortably fit. Dogs of all sizes also change their behavior in a uniform way to negotiate short openings. When holding a stick, dogs did not initially change their behavior but are able to negotiate through an opening with experience. Researching how dogs navigate through a changing environment may be a fruitful way to begin to understand their sense of themselves.

Abstract

Very little research has focused on canines’ understanding of their own size, and their ability to apply this understanding to their surroundings. The current study tests domestic dogs’ judgment of their body size in relation to a changing environment in two novel experimental situations: when encountering an opening of decreasing height (Study 1) and when negotiating an opening when carrying a stick in their mouth (Study 2). We hypothesized that if dogs understand their own body size, they will accurately judge when an opening is too small for their body to fit through, showing longer latencies to approach the smaller openings and adjusting their body appropriately to get through—although this judgment may not extend to when their body size is effectively increased. In line with these hypotheses, we found that the latency for subjects to reach an aperture they could easily fit through was significantly shorter than to one which was almost too small to fit through. We also found that the order of subjects’ adjustments to negotiate an aperture was invariant across individuals, indicating that dogs’ perception of affordances to fit through an aperture is action-scaled. Preliminary results suggest that dogs’ approach behavior is different when a horizontal appendage is introduced, but that dogs were able to alter their behavior with experience. These results are consistent with the hypothesis that dogs understand their own body size and the affordances of their changing environment.

Animal Cognition: The Self-Image of a Bumblebee

Knowing one's body dimensions is a core aspect of individual experience and self-awareness. A recent study illustrates how bees take into account their own body size both in preparation for and while traversing small gaps.

Dogs (Canis familiaris) recognize their own body as a physical obstacle

Mental representations of one’s own body provide useful reference when negotiating physical environmental challenges. Body-awareness is a neuro-ontogenetic precursor for higher order self-representation, but there is a lack of an ecologically valid experimental approach to it among nonhuman species. We tested dogs (N = 32) in the ‘body as an obstacle’ task. They had to pick up and give an object to their owner, whilst standing on a small mat. In the test condition we attached the object to the mat, thus the dogs had to leave the mat because otherwise they could not lift the object. Dogs came off the mat more frequently and sooner in the test condition, than in the main control condition, where the object was attached to the ground. This is the first convincing evidence of body awareness through the understanding of the consequence of own actions in a species where previously no higher-order self-representation capacity was found. We urge for an ecologically valid approach, and following of bottom-up methods, in studying modularly constructed self-representation.

Bumblebees perceive the spatial layout of their environment in relation to their body size and form to minimize inflight collisions

Animals that move through complex habitats must frequently contend with obstacles in their path. Humans and other highly cognitive vertebrates avoid collisions by perceiving the relationship between the layout of their surroundings and the properties of their own body profile and action capacity. It is unknown whether insects, which have much smaller brains, possess such abilities. We used bumblebees, which vary widely in body size and regularly forage in dense vegetation, to investigate whether flying insects consider their own size when interacting with their surroundings. Bumblebees trained to fly in a tunnel were sporadically presented with an obstructing wall containing a gap that varied in width. Bees successfully flew through narrow gaps, even those that were much smaller than their wingspans, by first performing lateral scanning (side-to-side flights) to visually assess the aperture. Bees then reoriented their in-flight posture (i.e., yaw or heading angle) while passing through, minimizing their projected frontal width and mitigating collisions; in extreme cases, bees flew entirely sideways through the gap. Both the time that bees spent scanning during their approach and the extent to which they reoriented themselves to pass through the gap were determined not by the absolute size of the gap, but by the size of the gap relative to each bee's own wingspan. Our findings suggest that, similar to humans and other vertebrates, flying bumblebees perceive the affordance of their surroundings relative their body size and form to navigate safely through complex environments.

Shells as 'extended architecture': to escape isolation, social hermit crabs choose shells with the right external architecture

Animals' cognitive abilities can be tested by allowing them to choose between alternatives, with only one alternative offering the correct solution to a novel problem. Hermit crabs are evolutionarily specialized to navigate while carrying a shell, with alternative shells representing different forms of 'extended architecture', which effectively change the extent of physical space an individual occupies in the world. It is unknown whether individuals can choose such architecture to solve novel navigational problems. Here, we designed an experiment in which social hermit crabs (Coenobita compressus) had to choose between two alternative shells to solve a novel problem: escaping solitary confinement. Using X-ray microtomography and 3D-printing, we copied preferred shell types and then made artificial alterations to their inner or outer shell architecture, designing only some shells to have the correct architectural fit for escaping the opening of an isolated crab's enclosure. In our 'escape artist' experimental design, crabs had to choose an otherwise less preferred shell, since only this shell had the right external architecture to allow the crab to free itself from isolation. Across multiple experiments, crabs were willing to forgo preferred shells and choose less preferred shells that enabled them to escape, suggesting these animals can solve novel navigational problems with extended architecture. Yet, it remains unclear if individuals solved this problem through trial-and-error or were aware of the deeper connection between escape and exterior shell architecture. Our experiments offer a foundation for further explorations of physical, social, and spatial cognition within the context of extended architecture.

Mental representation and episodic-like memory of own actions in dogs

We investigated whether dogs remember their spontaneous past actions relying on episodic-like memory. Dogs were trained to repeat a small set of actions upon request. Then we tested them on their ability to repeat other actions produced by themselves, including actions performed spontaneously in everyday situations. Dogs repeated their own actions after delays ranging from a few seconds to 1 hour, with their performance showing a decay typical of episodic memory. The combined evidence of representing own actions and using episodic-like memory to recall them suggests a far more complex representation of a key feature of the self than previously attributed to dogs. Our method is applicable to various species, paving the way for comparative investigations on the evolution and complexity of self-representation.