An Overview of Recent Research Into Higher-Order States of Consciousness in Animals

The question of whether any animals have minds like ours (with a capacity for language, self-awareness, abstract thought or an appreciation of the relationship between means and ends) needs to be addressed. The ethical implications of an affirmative answer are obvious: animals that can use language, have a self-concept, entertain abstract concepts or act intentionally may well qualify as moral agents and be entitled to the same basic rights as people are.

The possibility that some animals can use language certainly deserves to be taken seriously, as the following examples show:

• Kanzi, a bonobo ("pygmy" chimpanzee) whose trainer, Sue Savage-Rumbaugh, credits him with the linguistic ability of a two-and-a-half year-old human infant, has a receptive vocabulary of about 500 words, responds appropriately to the command "Go get the carrot that's in the oven" even when multiple carrots are present, and can distinguish the command "Make the snake bite the doggie" from "Make the doggie bite the snake" when playing with toy animals (Savage-Rumbaugh et al., 1998).
• Dolphins at the University of Hawaii can respond appropriately to gestural commands such as "right hoop left Frisbee fetch" ("Take the Frisbee on your left to the hoop on your right"), even when the commands are novel. They ignore nonsense commands. Even college students trained for four months in the dolphins' gestural language responded no more accurately than the dolphins (Hart, 1996, pp. 75 - 76).
• German researchers have found a border collie named Rico who can understand more than 200 words and can learn new ones as quickly as many children. The dog also proved capable of elementary reasoning: when ordered to fetch a toy whose name he had never heard before from a room full of familiar toys and one unfamiliar toy, he usually selected the unfamiliar toy. "Apparently he was able to link the novel word to the novel item based on exclusion learning, either because he knew that the familiar items already had names or because they were not novel," said Julia Fischer of the Max Planck Institute in Leipzig (article by Randolph Schmid, reported in The Canberra Times, 17 June 2004).
• Irene Pepperberg has been working with an African grey parrot named Alex for nearly 25 years, and more recently with two other parrots. In a recent interview with Robyn Williams on "The Science Show" (23/02/2002), she described Alex's abilities:

  I don't like to call it language. I'm very careful about that because, for example, you could not interview Alex the way you're interviewing me but he does have a complex two-way communication system. He's learned labels for about 50 different objects. He knows seven colours. He knows five shapes. He knows quantities up to and including six. He has concepts of category, concepts of big or smaller, concepts of same and different, concepts of number, functional use of phrases like, "I want x" and "Want to go y" and he combines his labels to identify requests, refuse and quantify more than about 100 different things.

Self-awareness is another controverted area. While many species, such as baboons, elephants and African grey parrots, can use a mirror to guide their behaviour, e.g. to find hidden food (Budiansky, 1998, p. 171; Reiss and Marino, 2001), the capacity for true mirror self-recognition has only been demonstrated for great apes (Gallup, 1970), and more recently, dolphins (Reiss and Marino, 2001). Whether this indicates true self-awareness or merely awareness of one's own body continues to be a matter of philosophical debate (Leahy, 1994, pp. 145 - 146; Budiansky, 1998a, pp. 167 - 171).

Some authors have also argued that great apes, baboons, opossums, piping plovers and even fireflies are aware of other individuals' mental states, which enables them to deceive others (Griffin, 1994; Whiten and Byrne, 1997). However, this interpretation has been queried by other researchers who propose that these animals' deceptive behaviour may be the product of a built-in behavioural program, honed by millions of years of natural selection (e.g. Budiansky, 1998a, pp. 29 - 33).

Abstract thought has attracted a lot of interest. Attention has focused on animals' alleged abilities to categorise objects, to follow rules, to grasp abstract concepts like "same" and "different", and to count.

Pigeons, for example, have been trained to categorise photographs into four classes: cats, cars, chairs and flowers. The pigeons were also able to categorise pictures that they had not seen before. Further work (Young and Wassermann, 2001) suggests that pigeons can reliably discriminate between arrays of novel pictures that are the same and different:

The bird's and the nonhuman primate's demonstrated abilities to learn and use an abstract relational concept make one thing clear: nonhuman animals are capable of conceptual feats heretofore thought to be solely within the ken of the human species.

However, another researcher, Huber (2001) admits:

[W]e do not know whether pigeons have concepts and use them to solve category problems.... In fact, perceptual mechanisms alone may explain the results of these experiments... [T]here is at present no coherent account of what animal concepts might involve (clusters of features or anything more abstract or knowledge-based).

Even more intriguingly, it has been shown that honeybees can recognise shapes under a variety of viewing conditions (Zhang, Srinivasan and Collett, 1995), group objects into different categories, such as flowers, trees and landscapes (Zhang, 2002), learn abstract rules such as "Turn left when you see a green object, right when you see a blue one" (Zhang, Bartsch and Srinivasan, 1996) and even distinguish "same" from "different" (Giurfa, Zhang, Jennett, Menzel and Srinivasan, 2001). However, the interpretation of these results is still unclear. As Zhang puts it:

We are still not sure whether honeybees need abstract representation such as a concept for doing these tasks ... We discussed ... whether the bee needs an abstract concept or simply a sort of adaptive filtering operation. This is still an open question (personal e-mail, 30 December 2002).

Can animals count? A recent study (Brannon and Terrace, 2000) has shown that rhesus monkeys can easily learn to order pictures in terms of the number of items they contain. And, unlike any previous study, the researchers found that the monkeys could successfully transfer their ability to order pictures containing one to four items to correctly order pictures containing five to nine items. Circles, ellipses, squares and diamonds of various sizes and colors were randomly displayed in groups of one, two, three and four elements on a touch video screen. Monkeys were trained to touch the displays on the screen, in ascending order - the display with one element first, the one with two elements next, and so on up to four - or in descending order. (The displays were carefully designed to avoid giving the monkeys inadvertent cues based on size or area of the displays.) The monkeys' performance did not falter when new displays were added, or even when they were exposed to larger groups of five to nine elements, which they had not seen before. While the findings have been hailed as very impressive, caution is called for in interpreting the results: the monkeys may simply have a notion of "more" or "less", without being able to count, as we do. They may or may not have an abstract concept of number.

Tool use has been cited as evidence of an ability to understand the relationship between means and ends. Recently, a crow named Betty repeatedly displayed the ability to take a straight piece of wire, craft it into a hook with her beak, and use it to snag a piece of meat in a tube. She had seen and used supplied wire hooks before but had not seen the process of bending. The crow even used different methods to fashion the hooks on different occasions. The method used by the crow was different from those previously reported and would be unlikely to work with natural materials. She had little exposure to and no prior training with pliant material, and had never been observed to perform similar actions with either pliant or non-pliant objects. The crow's ingenuity appears to surpass anything observed to date in chimpanzees (Weir, Chappell and Kacelnik, 2002).

Writers such as Griffin have argued that tool use is evidence of conscious thinking, because "tool use, and especially the preparation of tools, constitutes an especially distinct separation of specialized behavior from the goal attained" (1994, pp. 101 - 102). But as Budiansky points out, when we talk about tool use (1998a, pp. 122 - 128) we enter a philosophical thicket, relating to such issues as:

• What counts as tool use - for example, is it tool use when an elephant scratches its back against a tree?; Is the tool use stereotypical (as in the case of the digger wasp) or flexible (as with chimps and crows)?;
• Can cases of tool use by animals be simply explained in terms of their natural ability to hold and use objects (e.g. because they have their hands free, as apes do), an extension of their basic instincts (e.g. birds, which use sticks to pry out insects from a crevice, have an underlying instinct to do the same with their beaks) or an evolutionary adaptation to their ecological niche (e.g. when elephants use tools, they generally hold vegetation in their trunks for swatting flies or scratching themselves)?;
• Should we rely on tool use as a criterion to measure animals' intelligence, or should we, as Euan Macphail suggests, assume as a working hypothesis that all animals are equally smart, and that dogs would make tools if they had hands like those of chimps?; and most importantly,
• Do the instances of tool use observed in animals show a genuine appreciation of the relationship between a means and an end? (Capuchin monkeys in the wild, for instance, use sticks to kill snakes, hit other monkeys, and dig for food, but laboratory tests show that when given a choice of sticks for removing a peanut from a clear Plexiglas tube, they show no insight as to how to use the sticks.)

I shall discuss methodological considerations in more detail below. Here, I would like to emphasise that while I think that a biologically based, "bottom-up" methodology is appropriate for deciding whether animals have mental states, I do not believe it is appropriate for deciding whether they have mental states on a level comparable with ours. In my opinion, the latter issue is best decided by following a "top-down" approach, looking at paradigm cases of acts which manifest these "higher level" mental states, rather than borderline cases. The paradigm cases I have in mind here are human intentional acts that take place in the public arena - acts such as exchanging rings in a wedding ceremony, signing a will, casting a vote, or planning a hunting expedition. It is impossible to understand the significance of these acts except by attributing beliefs, attitudes, desires and intentions to the parties involved. Contrary to the assertions of some philosophers who deny the existence of mental states, or define them in terms of underlying physical events, I will argue that the mental aspect of these public intentional acts is irreducible, and cannot be explained away by re-defining them as physical states, events or dispositions, even though they presuppose these states of affairs.

As I see it, the danger of focusing on borderline cases is that it creates an incentive to "dumb down" the irreducibly intentional aspect of our public acts, and blur important distinctions between, say, sensations and mental representations, or between drives and desires, or between action selection and choice.

I also reject the methodology of focusing on "private" mental events, without reference to public states of affairs. For some philosophers (e.g. Chalmers, 1996), the most salient feature of a mental state is its subjectivity. I believe that such an approach makes it impossible to satisfactorily resolve questions about other minds. While the "inner feel" of a mental state (say, a twinge of pain) is undeniably mental, its very privacy stymies any effort by an outsider to understand what is happening to its subject. To do this, we need to focus on public events - "She's yelling because she just stepped on a tack."

While discussing whether any animals have mental capacities like ours, I shall confine myself to the most promising candidates for having these abilities - especially cetaceans, great apes, certain species of birds, and honeybees (because the complexity of their social structure and dance "language" merits examination).