Abstract and Keywords
Uncovering similarities and differences between human and animal behavior is a key concern of the field of comparative psychology. The subfield of comparative psychology that is especially concerned with cognitive processes in human and nonhuman behavior is called comparative cognition. We deem comparative cognition to fall squarely within the realm of natural science and to be of vital importance to behavioral psychology and evolutionary biology. Comparative cognition is generally concerned with mechanistic matters, physiological interpretation, and experimental investigation; a rival school, cognitive ethology, is more inclined to philosophical matters, mentalistic interpretation, and naturalistic observation. Beyond this scholarly rivalry, we suggest that the experimental study of animal intelligence should greatly advance our understanding of behavioral adaptation and its evolution in the animal kingdom.
1A. At first, the allure is weak; there is a vague yearning and a mild agitation. Ultimately, the strength of the desire grows irresistible; its head turns sharply and it skitters across the uneven floor to caress the object of its affection with consummate rapture.
1B. A coin is drawn toward a magnet.
2A. A grim sense of foreboding wells up in the prey as the jaws of the predator draw near. Then, jagged teeth tear deeply into the succulent tissues of the defenseless prey. Excruciating pain sears through its flesh until the predator’s canines pierce the prey’s heart.
2B. A boy eats an artichoke.
3A. The slight chill gradually becomes a wintry frost. Decisive action is initiated with the clear goal of returning the ambient temperature to a balmy radiance.
3B. A thermostat activates a furnace.
Scientific descriptions and explanations of natural happenings are supposed to be objective, materialistic, and mechanistic, as is the case for some of the above accounts (those labeled B) of three everyday events. In other of the above over-dramatized accounts (those labeled A) of the same events, the proffered mentalistic interpretations appear to be gratuitous, if not downright preposterous, given our current understanding of metals, vegetables, and machines.
Mentalistic explanations of behavior and cognition in human and nonhuman animals may be equally needless; after careful experimental scrutiny, these mentalistic accounts too may seem ridiculous. Natural science has, indeed, succeeded in supplanting superstition and religion as explanations for countless other worldly events—from eclipses and the tides to infectious diseases and the circulation of the blood.
(p. 2) What, then, is the relevance of mentalism to the present volume, which is concerned with the intelligence of nonhuman animals? Quite simply, mentalistic accounts of animal behavior and cognition were proposed early in the history of comparative psychology by none other than Charles Darwin (1871/1920). After the rise of behaviorism, mentalism fell out of favor.
Surprisingly, mentalistic accounts have assumed contemporary significance due in part to the writings of the late D. R. Griffin, founder of the school of inquiry called cognitive ethology, whose prime aim is to analyze the possible conscious thoughts and experiences of nonhuman animals (see Griffin, 1976, for the first announcement of the field; see Mason, 1976, for the first critical appraisal of the field; see Griffin, 1992, for a more recent statement of the agenda of cognitive ethology and a review of the behavioral evidence that workers in the field adduce in support of this approach; and see Yoerg, 1992, and Yoerg & Kamil, 1991, for comprehensive critiques of the writings of cognitive ethologists). At least one of its most ardent supporters considers the main accomplishment of cognitive ethology to be that the very ideas of animal thinking and consciousness have gone from being “heretical” to “respectable” (Jolly, 1991).
Putting aside the matter of respectability, we wish to take the present opportunity to place cognitive ethology into logical and methodological perspective as well as to lobby on behalf of what we and others believe may be a preferable alternative to this mentalistic movement in behavioral science. The other scientific school—what current workers call comparative cognition—counts among its growing members most of the contributors to the current volume.
Our introductory chapter therefore discusses a series of central issues in the study of cognition that separate these two prominent approaches to the comparative study of human and animal cognition. After reviewing this chapter, the reader should be better able to appreciate the nature of these approaches and the notable disparities between them (also see Wasserman, 1993, 1997; Wasserman & Blumberg, 2010). This deeper appreciation should further help readers to understand the methodological and theoretical positions espoused by the authors of the collected chapters.
Central Issues in the Comparative Study of Cognition
Definitional and Observational Concerns
Few things set the animal world so dramatically apart from the rest of nature as does cognition—an animal’s ability to remember the past, to choose in the present, and to plan for the future. To the best of our knowledge, the human and nonhuman animals on our planet are the only living beings that evidence cognition. (The continually controversial case of cognition and the inanimate digital computer will not concern us here; see Blakemore & Greenfield, 1987, and Wasserman, 2009, for discussions of this intriguing issue.)
Despite the remarkable capacity, intricacy, and flexibility of adaptive behavior, cognition is not a magical or supernatural power; it is the natural product of the biological activity of the brain. Elucidating the workings of the brain is undoubtedly one of the most daunting challenges ever undertaken by the human species. The current excitement that is being generated by discoveries in the field of neuroscience testifies to the importance of this matter.
Unlike the operation of other bodily systems (like respiration), whose activity is usually directly observed in the isolated responses of particular organs (like the lungs), cognition is usually indirectly evidenced through the diverse responses of many different effectors, generally the skeletal muscles (although emerging methods in neuroscience herald the advent of more direct measures of brain activity). Hence, a youngster may sing, hum, or whistle a tune; play it on a piano, xylophone, or trumpet; tap out its rhythm with a stick on a drum; or write out its score with a pen on a sheet of paper. All of these various behaviors divulge her musical knowledge (for more on the substitutability of different behaviors to achieve a common end, see Rachlin, 1992, and Tolman, 1932). Therefore, although the core of cognition lies in the activity of the brain, we usually learn of cognition via what the early comparative psychologist Romanes (1883/1977) dubbed “behavioral ambassadors” (Wasserman, 1984).
Unequivocal distinctions between cognition and simpler Pavlovian and instrumental learning processes, as well as other behavioral or physiological processes like reflex action, maturation, fatigue, and motivation, are devilishly difficult to devise. There is often spirited disagreement among researchers on the merits of these distinctions, as when workers try to explain the occurrence and integration of elaborate behavior patterns like courtship rituals.
Many cognitive processes may be behaviorally indistinguishable from simpler learning processes. For example, one may learn and remember a telephone number, say 987-2468, by repeatedly saying the number aloud (i.e., learning by rote), considered (p. 3) by many theorists to represent a simple learning process. Alternatively, one may notice that the telephone number contains digit patterns like the descending serial order 9-8-7 and the even-number sequence 2-4-6-8, a cognitive process. Unless clear evidence is provided that a more complex cognitive process has been used, C. Lloyd Morgan’s famous canon of parsimony obliges us to assume that it has not; we must then conclude that a simpler associative process can account for the learning.
The challenge then is to identify flexible behavior that cannot be accounted for by simpler learning mechanisms. Thus, a cognitive process is one that does not merely result from the repetition of a behavior or from the repeated pairing of a stimulus with reinforcement. Cognitive processes often involve emergent (untrained) relations. Furthermore, because simple learning is assumed to generalize to physically similar stimuli or contexts, in order to qualify as a cognitive process, the emergent relations cannot involve stimuli or relations that are physically similar to those that were explicitly trained.
For example, if one wanted to show that a pigeon had the concept of identity, then one might train a pigeon to match red and green hues (i.e., to select red rather than green when the initial stimulus is red, but to select green rather than red when the initial stimulus is green). If one later tested the pigeon with orange and teal stimuli and one found good transfer, then one could not assume that the concept of identity had been demonstrated because orange is similar to red and teal is similar to green. On the other hand, if one tested the pigeons with stimuli that were not differentially similar to the training stimuli (e.g., black-and-white shapes such as circle and square), then evidence of good transfer might suggest that an untrained relation had emerged. Thus, the demonstration of cognitive behavior implies that simpler learning processes cannot account for the demonstrated actions (for an unconventional argument concerning parsimony in cognitive interpretations, see Byrne & Bates, 2006).
Studying the Generality of Cognition
Humans are far from unique in exhibiting cognition. Comparable investigative methods have disclosed that nonhuman animals also exhibit complex and flexible behaviors that most observers would confidently conclude disclose cognition, if members of our own species had displayed the same behaviors in the same circumstances. One of Darwin’s enduring legacies is his provocative proposal of mental continuity between human and nonhuman animals: “The difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind” (1871/1920, p. 128).
More infamous was Darwin’s penchant to infer a wide variety of cognitive and emotional functions—including love, memory, attention, curiosity, imitation, and reason—from numerous anecdotes related by pet owners, naturalists, and zookeepers. These anecdotists were not always impartial observers or careful recorders of either the behavior in question or the conditions that promoted the behavior. As interesting and suggestive as these anecdotes were to Darwin, they could not stand the stringent tests of scientific scrutiny, for they were of dubious objectivity and reliability. The anecdotal method simply would not do to establish a science of comparative cognition. A new and different approach was needed to study the generality of cognition.
Comparative Cognition: A Natural Science Approach
Uncovering similarities and differences between human and animal behavior is a prime concern of the field of comparative psychology. The subfield of comparative psychology that is expressly concerned with cognitive processes in human and nonhuman behavior is called comparative cognition.
In contrast to Darwin’s naïve reliance on anecdotal evidence of questionable veracity and replicability, comparative psychologists now use investigative methods that are wholly objective in order to study advanced behavior and cognition in nonhuman animals. Precise control over relevant factors and systematic variation in pertinent organic and environmental parameters encourages researchers in the field to adhere closely to the experimental method.
As most students of behavior are aware, I. P. Pavlov, in Russia, and E. L. Thorndike, in the United States, devised highly reliable and objective techniques for studying learning in nonhuman animals. Much of the progress in the experimental study of comparative cognition has been due to the creative application or modification of their two basic methods.
In addition, respect for Morgan’s canon of parsimony tempers the tendency for workers in the field of comparative cognition to invoke overly elaborate interpretations of the behavioral evidence, as Darwin and his early followers were prone to do. As Yoerg and Kamil (1991) echoed a century after Morgan advanced his canon, “We should be circumspect in our evaluation of the level or complexity of explanation the evidence demands” (p. 277).
(p. 4) Experimental Locale
Rare or remarkable natural behaviors by animals often provide the impetus for careful experimental investigations in laboratory settings. Movement from the field to the laboratory is often necessary if the biological mechanisms controlling the behavior are to be properly pinpointed and if rival interpretations of the behavior are to be systematically explored and convincingly eliminated. Appropriately designed field experiments are also a most enlightening brand of investigation.
At other times, the scientific objective is to discover whether some human cognitive feat can be exhibited by nonhuman animals (this approach is exemplified by the studies of conceptual behavior by pigeons that have been reviewed and analyzed by Wasserman & Astley, 1994, as well as by the research on directed forgetting in nonhumans that has been reviewed by Roper & Zentall, 1993). Such demonstrations not only speak to the species generality of the cognitive process in question, but also provide essential empirical information for understanding the possible evolutionary origins of cognition. Most workers have found the laboratory to be a particularly suitable venue for probing the cognitive limits of nonhuman behavior, due to the ease of varying situational variables and recording behavioral responses.
Zentall (1993), in particular, has examined the longstanding interest in exploring the limits of animal intelligence and the problems posed by naturalistic study alone. He concluded that it is not unreasonable to expect that evidence of cognitive behavior will be found in an “unnatural” laboratory setting, despite the fact that animals may exhibit little sign of cognitive behavior when they are observed in their natural environment. Zentall suggested that laboratory experimentation is especially useful because it may be the only way to elicit latent cognitive strategies whose use results in higher levels of, or more efficient, behavior. It may be necessary to expose an animal to artificial procedures both to rule out explanations of behavior in terms of simple learning principles and to induce the animal to deploy advanced cognitive abilities.
Hence, the laboratory studies of animal behavior that are conducted by comparative psychologists are not substitutes for, but complements to, the careful naturalistic observations of field biologists and ecologists. What we learn in one setting must inform our understanding of what we observe in the other (Balda & Kamil, 1989; Riley, Brown, & Yoerg, 1986).
Cognition and Unobservables
Because cognition is not itself directly observable, the field of comparative cognition must (with great reluctance, it should be noted) refer to unobservables in the description and explanation of behavior (more about this issue can be found in Honig, 1978; Mackenzie, 1977; Riley et al., 1986, Wasserman, 1981, 1982, 1983; and Zuriff, 1985). Many of the unobservables that are used in the field of comparative cognition are of the same “functional” sort as those that are commonly invoked by chemists and physicists (also see Pribram, 1978).
For example, the term memory describes those cases when an organism’s present behavior is a function of a past stimulus: an animal is thus said to remember a light if it responds differently to the light on its first and second occasions. In a parallel way, a capacitor can be said to have stored charge when the same current applied to it on a second occasion leads to a smaller increase in electrical potential than occurred on a first occasion, thereby yielding a lawful functional relation between applied current and stored charge. Similar functional considerations guide the deployment of the cognitive construct of attention.
Although interpretive dangers attend the study of cognition in nonhuman animals, there are safeguards to those dangers. One of the founders of modern research on comparative cognition, W. K. Honig, assessed the merits of this approach in the following way: “The analysis is plausible because it places cognitive process and cognitive behavior within the framework of a functional and experimental analysis of behavior. … There is nothing magical or mysterious about the relevant experimental or criterion behaviors, and thus processes remain within the realm of behavioral identification and analysis. We do not need a new kind of psychology to deal with cognitive events” (1978, p. 11).
Other unobservables are of a distinctly different, mentalistic nature and are scrupulously avoided by natural scientists—whether they are psychologists or physicists. These mentalistic notions spring from our own private experience and they are further shaped by an enculturation process that is strongly rooted in Cartesian dualism and “folk” psychology (Michel, 1991, offers an incisive analysis of the fruitlessness of folk psychological theory as it has been applied to both human and nonhuman animals). Such mentalistic ideas are well represented by three of the accounts that began this introduction.
(p. 5) Sometimes, however, aspects of ideas that began as vague mentalistic thoughts based on subjective experience can be operationalized and empirically studied—at least within a limited framework. An example is the study of “theory of mind.”
If you have a theory of mind, then you should be capable of understanding what others may or may not know. This notion does not require that you have the ability to read the mind of another person, just that you understand that for someone to know something, some experience with it is required.
When studied in children, theory of mind may take the form of the following scenario. Two children, Sally and Billy, are shown the contents of two covered boxes: one is empty, whereas the other contains a small toy. Sally is then asked to leave the room and the experimenter moves the toy to the other box. The experimenter then asks Billy, “When Sally comes back into the room and I ask her, ‘Where is the toy?’, what will she say?”
When tested in this way, young children, who presumably do not have theory of mind, indicate the veridical (changed) location of the toy. Older children, however, understand that Sally did not see the toy being moved and therefore Sally should believe that the toy is where it was originally. Older children can therefore infer what Sally knows and does not know. In this case, language provides an important tool for the study of cognitive behavior in humans, but carefully designed experiments may allow researchers similar access to cognitive processes, analogous to theory of mind, in nonverbal animals (see Premack & Woodruff, 1978).
Cognition and Mentalism
Especially when mentalistic notions are applied to other living beings, they suggest the analogous experience of some private thought or feeling (for an early discussion of mentalistic inference via this anthropomorphic analogy, see Romanes, 1883/1977; for a more recent discussion of anthropomorphism in behavioral science, see Kennedy, 1992). For instance, a rat that is placed into a cold environment will learn to press a lever that briefly activates a heat lamp. Some individuals might say that the rat does so because it “feels” cold, because it “wants” warmth, and because it “knows” that pressing the lever will produce heat. But it is crucial to realize that any “feeling,” “wanting,” and “knowing” are not necessarily in the rat, but may reside in the person projecting onto the rat his or her own private experiences. Nothing in the rat’s behavior demands that we use these mentalistic terms, a point that can forcefully be made by considering the similar behavior of a thermostat: a human-made device that we staunchly believe is quite unable to think or to feel as we do.
Of course, the use of mentalistic terms is common in everyday speech and in some circles of scientific and philosophical discourse. Its ubiquity suggests that this explanatory style may be innate (Humphrey, 1978). But it may be learned; children are frequently instructed by their elders that “the cat wants to have its head rubbed,” that “mom’s car didn’t feel like starting today,” or that “nature abhors a vacuum.” Whatever its provenance (for further conjectures on the origins of mentalism, see Kennedy, 1992, and Povinelli, 1993), many individuals believe that mentalism is not a sound basis for a natural science of cognition—whether of humans or of other animals. These theorists consider that mentalism is a prescientific mode of explanation that may hamper progress in the behavioral and brain sciences (for more on this view, see Kennedy, 1992; Skinner, 1977, 1985).
These points notwithstanding, mentalism is not a theoretical affliction that affects only the soft-headed among us. No less than the Nobel Laureate physiologist Ivan P. Pavlov once adopted a mentalistic approach to understanding the conditioned reflexes that he and his coworkers discovered in their studies of canine digestion.
The beginning of that story is familiar enough: Pavlov and his Russian colleagues serendipitously observed that hungry dogs salivated not only to food in the mouth, but also to stimuli that were repeatedly paired with food, like the familiar sight of the experimenter entering the room holding a bowl of food. The end of the story is also well known: Pavlov vigorously insisted that natural scientific laws of association formation could be experimentally established that linked—via the dog’s neural machinery—temporally contiguous stimuli, like the sight of the food bowl with food in the mouth.
What is missing from most textbooks is an account of the extraordinary difficulty that Pavlov and his collaborators had in deciding just how to go about investigating and interpreting their groundbreaking observations. In the 1928 book chronicling his first 25 years of conditioning research, Lectures on Conditioned Reflexes, Pavlov describes this fascinating story as involving two opposite paths to comprehending conditioned reflexes: the mentalistic approach and the scientific approach.
(p. 6) According to the mentalistic approach, we should be mainly interested in the internal or subjective world of the dog rather than in its overt actions. This approach assumes that the internal world of the dog—its thoughts, its feelings, and its desires (if it has any)—is analogous to our own. Pavlov and his colleagues actually entertained this approach prior to 1903 in order to understand the then-called “psychical” secretions of their dogs to signals for food.
Using the mentalistic approach, the researchers tried to explain their findings by “fancying the subjective condition” of their dogs. Unfortunately, all that came from these many musings were endless controversies and unverifiable personal opinions. This interpretive breakdown forced the researchers to abandon what Pavlov suspected was an inborn inclination for people to adopt a mentalistic interpretation and to promote a less familiar but more productive objective approach. This analytical transition from mentalistic interpretation to a natural science approach was not an easy one to make; indeed, Pavlov described the process as involving persistent deliberation and considerable interpersonal dispute.
From a different perspective, other authors have argued on behalf of mentalism as a bountiful source of fresh hypotheses for proper scientific scrutiny. Famous among those authors was Tolman (1938), who wrote, “I, in my future work intend to go ahead imagining how, if I were a rat, I would behave” (p. 24; further discussion of this proposal can be found in Burghardt, 1985, and Kennedy, 1992). As long as mentalistic musings are used purely heuristically, like the fanciful flights that are said to have inspired August Kekule’s hypothesization of the benzene ring, they may be beneficial; they are, in this case, unproblematic. The problem is that too many workers pursue mentalism to its more troublesome extremes.
Mentalism and Cognitive Ethology
Several cognitive ethologists have contended that our private experience is so profound and salient that to exclude it from a scientific analysis is to leave out a necessary ingredient to a “complete” understanding of cognition and behavior (see Feigl, 1967, p. 138, for a recounting of Einstein’s colorful comments on the matter). Cognitive ethologists have further claimed that although at present we lack the critical methodological tools for directly assaying consciousness in other organisms, these techniques may be on the immediate horizon. We must, they implore, not close our minds to the possible development of such “windows” into others’ minds (Ristau, 1991).
Personal experience is indeed basic and striking; it was utterly undeniable to René Descartes (1641/1988). Yet, experience is inherently private. As Lubinski and Thompson (1993) have observed, “Experiential phenomena are directly accessible via one road, a road on which only one person travels” (p. 668) (also see Baum, 1993). Because of the impossibility of independent observers ever agreeing on the experiential “facts” at issue, many theorists have suggested that private experience simply falls outside the ken of natural science—a positively public business. The development of objective “windows” into others’ minds is thus better considered to be the stuff of science fiction than of science fact. It is extraordinarily unlikely that any behavioral, introspective, or physiological methods will ever allow us to experience the thoughts and feelings of another organism—human or nonhuman.
Critically, cognitive ethologists’ fascination with interspecific communication as such an objective window is probably not the royal road to shared private experience: “Asking another [organism] what it is thinking may give you another piece of behavior, but it will never give you direct access to its mental state” (Laasko, 1993). Let us not forget Wittgenstein’s famous (1953) aphorism, “If a lion could talk, we could not understand him.” Appeal to the eventual development of objective mental “windows” appears to be, at best, wishful thinking and, at worst, an obstacle to real progress in the scientific analysis of complex behavior and cognition. “If the history of other sciences can be a guide, the study of animal behavior will progress only to the extent that we can devise techniques and metaphors that avoid imputation of human mental phenomena to animals which result from metaphoric extensions of our folk psychology” (Michel, 1991, p. 268). To many past and present workers in the field of comparative cognition, what is generally called operational behaviorism (Zuriff, 1985) provides those progressive techniques and metaphors.
Simply put, the notion of “windows” into others’ minds appears to be misguided. Behaviors—be they simple or complex, be they verbal or nonverbal, be they those of human or nonhuman animals—are purely the product of biological mechanisms. When we infer private experiences in others from their public behaviors, we are not using a metaphorical “window” at all, but rather a “mirror.” We see ourselves in the behavior of others. Even more perilously, (p. 7) we see our inner selves reflected in the outward behavior of others. It is, of course, reassuring to see ourselves when we look into a mirror; to see someone or something else would be most discombobulating. We may thus be comforted that other animals seem pretty much like us when we describe and interpret their behavior in terms of our own private experience.
Our tendency to infer mental states in animals may be an extension of our ability to project onto other humans our own mental states. We infer what their mental state would be if we were to behave similarly under similar circumstances. Such inferences may have practical value in our social relations with other humans. For example, we express our sorrow to a friend who has lost a parent or who has been involved in an accident. But we should not confuse any possible social function of assuming similar mental states between ourselves and others (sympathy or empathy) with an objective understanding of those states. When we express sympathy, it does not much matter if we are wrong; our expression of concern alone is appreciated because others are grateful for our thoughts. In those cases, the assumption of a common mental or emotional state may play a social role, but that state itself is not the subject of science. When we make assumptions about the similarity of our own mental states to those of other animals, this vision may be so distorted by the lens of mentalism that a clear view of the animal mind can never be gained—and that is our true quest.
Finally, we might well ask what cognitive ethologists hope to gain by postulating the existence of conscious experience in animals other than a possibly false sense of completeness in treating both the “inner” and “outer” aspects of behavior (see Romanes, 1883/1977, for more on this distinction). Griffin’s answer is that, if animals do indeed have mental experience, then that experience may “affect the animals’ behavior, welfare, and biological fitness” (1978, p. 528). However, understanding any possible functional significance of mental experience must surely await the collection of convincing empirical evidence of that experience and the delineation of the mechanisms of its proximate causation. Many critics fear that this wait will be endless.
Might it not be better to pursue a purely objective analysis of behavior and cognition, one that judiciously avoids such treacherous concepts as mind and consciousness and that follows the proven path of natural science? This course of action was precisely what the early behaviorist H. S. Jennings proposed when he observed that “apart from their relation to the problem of consciousness … the objective processes in behavior are of the highest interest in themselves. … [W]e need a knowledge of the laws controlling them, of the same sort as our knowledge of the laws of metabolism” (1904/1976, p. v).
The Agenda of Comparative Cognition
The myriad behaviors of humans and other animals persuade us that they remember the past, they choose in the present, and they plan for the future. On what behavioral, situational, and historical grounds do we make these cognitive inferences? What are the behavioral and biological mechanisms of remembering, choosing, and planning? Are humans special among all other animals in their processes of cognition? What, if anything, does language add to an animal’s ability to adapt to changing conditions of survival? These are some of the truly crucial, exciting, and answerable questions for a science of comparative cognition; these and other intriguing issues are carefully considered in the many chapters that follow.
The experimental study of animal intelligence should greatly advance our understanding of behavioral adaptation and its evolution in the animal kingdom. Perhaps we should simply get on with this task and leave mentalistic speculations to philosophers, whose theories of mind and conjectures about consciousness need not be bound by the constraints of natural science. We do need a science of comparative cognition. But that field “should not be loosely slung in a net of mentalistic verbiage. Rather, it should be defined as the rigorous, wholly scientific study of cognition in an ethological and ecological context” (Yoerg & Kamil, 1991, p. 278).
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