Cognitive psychology proposes yet another way to study the causal mechanisms of animal behaviour. The aim of cognitive psychology is to explain an animal’s behaviour in terms of its mental organization for information processing (that is, how the animal acquires, stores, and acts on information present in its world). By studying cognitive mechanisms of an animal, one may study how the animal perceives, learns, memorizes, and makes decisions.
Consider, for example, crows (Corvus brachyrhynchos) that crack walnuts open by dropping them from heights of 5 to 10 metres (about 16 to 33 feet) or more onto rocks, roads, or sidewalks. The birds generally avoid dropping the nuts onto soil, where they would be unlikely to break open. Remarkably, the crows can discriminate between black and English walnuts, for they drop the harder black walnuts from greater heights. In addition, when a crow drops a nut, it takes into account the likelihood that a fellow crow might steal the contents before it can be retrieved. If fewer competing crows are perched nearby, the crow carries a nut higher into the air before releasing it. Thus, numerous processes of perception, learning, and decision-making activity underlie the crows’ nut-cracking behaviour.
Each of these processes may be analyzed. For example, how do crows judge the height from which to drop nuts? Do they have to learn to adjust the dropping height in relation to the type of walnut? When faced with the conflicting conditions of having a hard-shelled black walnut and seeing a number of other crows nearby, how do they decide what drop height to use?
Until the 1970s, students of animal cognition eschewed speculation about the unobservable processing of information, limiting themselves to explaining behaviours in terms of quantifiable relationships between stimuli and responses. Today, however, they make use of behaviour as a window into how an animal’s nervous system processes information. Students of cognition also emphasize the investigation of behaviours in which the animal does not simply respond to immediate stimuli but relies on stored representations of objects and events. For some investigators, mental representations of the environment are the essence of cognition. According to this view, known as the computational-representational approach, the experience of an animal results in the formation in the brain of isomorphisms between brain processes and events in the world. The brain then performs computations on these representations that are ultimately converted to behavioral outputs. For example, a bird assessing the availability of berries on a bush might store information about the time at which it finds each berry as it searches the bush. It might then convert this information, through a brain process equivalent to division, into a representation of the rate of berry collection.
It is possible, however, that the computational-representational approach exaggerates the richness and detail of animals’ representations and the complexity of the brain processes operating on them. A good illustration comes from studies of the mechanisms by which ants (Cataglyphis fortis) living in the Sahara desert navigate home after conducting a circuitous search for food (mainly dead insects). Such a search can take these ants 100 metres (about 330 feet) or more (equivalent to 10,000 body lengths) from the entrance of their underground nest. To get back home, the ants rely on landmarks as visual signposts to show the way. Originally, it was assumed that these ants and other insects that orient using landmarks are able to store their knowledge of the nest environs in maplike internal representations called “cognitive maps.” Doing so would give an ant tremendous flexibility in homing: equipped with a bird’s-eye knowledge of the terrain over which it travels, an ant could return even from points where it had never before been. The mental representation used by these ants in landmark guidance is, however, actually somewhat simpler. Experiments have revealed that each ant stores a two-dimensional visual template—a kind of snapshot—of the landmark array it saw when it left its nest. When returning to its nest, the ant moves so as to match the current visual image as closely as possible with the memorized template. The snapshot-matching mechanism, unlike the cognitive-map one, enables an ant to steer its way home only from points it has recently visited, as opposed to novel sites to which it might be displaced by an experimenter. Although this mental mechanism provides a less complete and less flexible solution to the problem of finding home, it is entirely sufficient for the problems that desert ants routinely face.
An unseen and therefore largely unappreciated aspect of behaviour is the use of decision-making rules or “Darwinian algorithms.” Organisms rely on these rules to process information from their physical and social environments and result in particular behavioral outputs that guide key behavioral and life-history decisions. Darwinian algorithms are made up of the sensory and cognitive processes that perceive and prioritize cues within an individual’s perceptual range. These inputs are then translated into motor outputs. A Darwinian algorithm may involve a stimulus threshold (such as “when the day-length exceeds 10 hours, migrate north”) or may depend on the occurrence of a cue that is normally associated with a fitness-enhancing outcome (such as “build nests in dense vegetation where chick survival is predictably high”). Darwinian algorithms are shaped through evolutionary time by the specific selective regime of each population. Which cues are relied upon depends on the certainty with which a cue can be recognized, the reliability of the relationship between the cue and the anticipated environmental outcome, and the fitness benefits of making a correct decision versus the costs of making an incorrect decision. In general, Darwinian algorithms underlying behavioral and life-history decisions are only as complex as is necessary to yield adaptive outcomes under a species’ normal environmental circumstances but not so complex as to cover all experimentally or anthropogenically induced contingencies.
An intriguing question in the study of animal cognition is the role of consciousness. Humans easily distinguish between merely responding to objects and being conscious of them. For example, while driving along a highway deep in thought or conversation, the driver may suddenly realize that he has not been conscious of the road for the past several miles. Indeed, it is well documented that humans can effectively perceive, memorize, process, and even act on objects and events without the kind of awareness that underlies a verbal report of consciousness. It is possible, therefore, that the behaviour of animals occurs without conscious awareness. However, given that humans have consciousness, it seems reasonable to suppose that individuals in other species, especially social species (such as primates), also experience at least a rudimentary form of consciousness. To think otherwise would be to presume an evolutionary discontinuity between humans and all other forms of life. Thus, the possibility that at least some of the behaviour of animals is accompanied by conscious thinking seems reasonable.
Although most students of animal behaviour accept the idea that animal consciousness is a likely possibility, some argue that it is not yet possible to know whether any particular animal experiences consciousness because it is a private, subjective, and, ultimately, unknowable state. In contrast, cognitive ethologists (a separate group of animal behaviourists), most notably American biophysicist and animal behaviourist Donald Griffin, argue that animals are undoubtedly conscious, since individuals from a wide variety of species behave with apparent intentions of achieving certain goals. For example, chimpanzees (Pan troglodytes) stalking a monkey high above them in the treetops will distribute themselves among the trees that would otherwise provide the monkey with an escape route and attack the creature simultaneously. Similarly, groups of female lions (Panthera leo) fan out widely and then coordinate their attacks on ungulate prey. In another example, a raven (Corvus corax), when presented with the novel situation of a meat morsel dangling from a long string tied to a perch, will study the situation briefly before it acts. Subsequently, the raven will quickly procure the meat by repeatedly pulling up a length of the string with its beak and clamping each length pulled up with its feet while sitting on the perch. Studies of the states and mechanisms of animal consciousness represent important frontiers of future research.
Ontogeny
Just as a thorough understanding of an animal’s morphology requires knowledge of how it develops before it hatches from an egg or emerges from its mother’s womb, a complete understanding of an animal’s behaviour requires knowledge of the animal’s development during its lifetime. To gain this knowledge, one asks how the individual’s genes and its experiences cause it to behave as it does. The ontogeny of behaviour is a subject which arouses considerable interest, perhaps because of the seeming contrast between humans and other animals in how behavioral skills are acquired. Whereas humans extensively adjust their behaviour based on experience (that is, through the process of learning), the behaviour of many animal species seems to be automatic, as if it were pre-programmed. And yet, if there really were a difference between humans and other animals in how behaviour develops, it would certainly be one of degree, not of kind.
Behavioral development is a field of study in which there have been intense clashes of opinion. Prior to the 1960s there existed a profound disagreement between European (particularly German) ethologists and American psychologists regarding methods and interpretations of such studies. The ethologists described many examples of animals showing complex behaviour patterns in response to particular stimuli under circumstances that seemed to preclude the opportunity for learning. Indeed, learning (based on external influences) was contrasted with genetic control of behaviour (based on internal influences). Austrian zoologist Konrad Lorenz, who won a Nobel Prize for his ethological studies, went so far as to classify behaviour patterns into two distinct categories: acquired and innate.
Regarding the latter, adult herring gulls (Larus argentatus) have a red spot on the lower tip of their bill. When these birds have food for their chicks, the adults point their bill downward while waving it slowly back and forth in front of the young. Newly hatched chicks will accurately peck at the red spot on the parent bird’s bill, suggesting that a herring gull chick possesses innate (that is, genetically based) knowledge of where to peck for food. Ethologists termed pecking behaviour a “fixed action pattern” to indicate that it was performed automatically and correctly the first time it was elicited, apparently regardless of the animal’s experience.
The psychologists, in contrast, assumed that experiences with the environment (that is, learning processes) were the main, or even exclusive, determinants of ontogeny. Accordingly, they saw nothing in the pecking behaviour of herring gull chicks that could not be explained by learning while still in the egg, conditioning, or by trial-and-error learning. For example, chicks might “learn” to peck before hatching as a result of the rhythmic beating of their heart, or they might have a pecking reflex and simply learn to associate a food reward with pecking at the parent’s bill. Moreover, a chick’s pecking accuracy improves with age, and after about two days it requires, in addition to the red spot, the complete configuration of an adult’s head and bill to elicit pecking.
What the acquired-innate dichotomy obscured is that learning is possible only after the animal has already been steered by its genes to develop its behaviour in a certain way. An animal may well learn, but which experiences are important to the development of its behaviour depend on those that have promoted the genetic success of its ancestors. Reciprocally, whatever experiences an individual already has had can influence how its genes are activated and thus can affect their subsequent role in shaping its behaviour. Modern animal behaviourists see the stark dichotomy of acquired versus innate as far too simplistic; no behaviour is either strictly innate or entirely learned. Rather, all behaviours are the result of a complex interaction between genes and the environment.
Behavioral genetics
The evidence is now compelling that genes influence behaviour in all animals, including humans. Indeed, an increasing share of biomedical research is devoted to the hunt for genes involved in human behavioral maladies such as alcoholism, obesity, schizophrenia, and Alzheimer disease. Often these studies are pursued using animal models with subjects that include mice, rats, and dogs with behavioral symptoms resembling those of humans. It is, therefore, unfortunate that the idea that genes affect behaviour is the subject of much heated and confused discussion. The principal point of confusion arises from equating genetic influence on behaviour with genetic determination of behaviour. To do so is to mistakenly believe that identifying genes “for” a behaviour implies that the gene controls, fully and inevitably, this behaviour. In actuality, to say that there are genes “for” a particular behaviour means only that within a population of individuals there exists genetic variation underlying some of the differences in this specific behaviour. To cite an example involving a morphological trait, the statement that there are genes for coat colour in guinea pigs (Cavia porcellus) or horses (Equus caballus) means that genetic variation in the guinea pig or horse population is responsible for some of the variation in coat colour.
Furthermore, identifying a gene that influences a behaviour does not imply that the behaviour is inevitable; there is considerable variation among behaviours in the relative importance of the individual’s genetic constitution and its environment to the expression of the behaviour. Occasionally, the possession of a particular form of a gene does consistently result in the individual having a particular form of a behaviour; more frequently, however, the form of the behaviour is due to a complex interaction between genes and environment.
The strength of the influence of genes on a particular behaviour is quantified by a genetic measure called “heritability.” Heritability is defined as the fraction of the total variation in a trait among individuals in a population that is attributable to the genetic variation among those individuals. The remaining source of the variation is, of course, the environment. Values of heritability range between zero and one. The smaller the environmental variation experienced by the individuals in a population, the greater will be the fraction of the total variation in the behaviour that is the result of genetic variation.
One way to measure the heritability of a behavioral trait is to determine the average values of the behaviour for the parents and offspring in a sample of families within a population and calculate the linear relationship between offspring values and parental values. The slope of this line reveals the heritability of the behavioral trait in that population. For example, the heritability of the calling behaviour that male crickets (Gryllus integer) use to attract females has been measured. In any one population, some males chirp away for many hours each night, others call for just a few hours, and still others almost never call. The heritability of calling duration for one Canadian population that was studied was 0.53. The value indicates that slightly more than half of the variation in calling duration arose because males differed genetically and slightly less than half arose from environmental differences. (For example, the more parasites a cricket had acquired, the less food he had obtained, and thus the less he might be able to call on a given night.)
The degree of genetic influence on a particular behaviour is not a fixed characteristic. Rather, heritability can vary greatly depending on how much environmental variation is experienced by individuals in the specific population being studied. Thus, regarding the calling behaviour of male crickets, if every male fed well, thereby eliminating several environmental influences on calling, the numerical value of heritability would be considerably higher.
Numerous studies involving diverse species, including humans, have detected some level of heritability for every trait that has ever been examined. For example, the mean value of heritability for morphological traits, such as body and wing length, is 0.46; for life history traits, such as fecundity and life span, is 0.26; and for behavioral traits, such as calling duration and fighting stamina, is 0.30. Thus, the genetic influence on the characteristics of individual animals falls generally between 30 and 50 percent for most traits.
