Evolution Of Emotions Research Paper

1. The Darwinian Legacy

Darwin did not see his Expression of the Emotions in Man and Animals (Darwin 1872) as a theory of the evolution of emotion itself, because he defined emotions as subjective feelings. Following Herbert Spencer, Darwin distinguished the emotions as those feelings caused by external states, in contrast to those caused by bodily states, such as hunger and pain. Later evolutionary theorists have preferred behavioral and physiological definitions of emotion, with the result that Darwin’s theory of the expression of emotions has been interpreted as a theory of the emotions themselves.

Darwin proposed three principles of the evolution of expression. The most important of these was the ‘principle of serviceable associated habits,’ which is a straightforward application of Darwin’s theory of instincts to the case of emotion. Darwin believed that instinctive behaviors derive from habits acquired by psychological reinforcement. The consistent acquisition of the same habit for many generations causes it to become a hereditary, or instinctive, behavior by the inheritance of acquired characteristics, in which Darwin was a firm believer. Most of the distinctive behaviors associated with particular emotions, such as the erection of the hair in fear, reflect long-since vanished lifestyles in which those behaviors were rewarded and reinforced in each generation until they were finally incorporated into the hereditary material as instincts. Darwin supplements this principle with two others, the ‘principle of antithesis’ and the ‘principle of direct action.’ His antithesis principle postulates an intrinsic tendency for opposite states of feeling to produce opposite behaviors. Darwin remarks of a submissive dog that:

Not one of the movements, so clearly expressive of affection, are of the least direct service to the animal. They are explicable, as far as I can see, solely from their being in complete opposition or antithesis to the attitude expressive of anger (Darwin 1872, p. 51).

Darwin explains the behaviors left over after the application of these two principles as the results of the ‘direct action’ of the nervous system. Excess nerve energy built up in an emotional episode is released in behaviors such as sweating and trembling for no other reason than that it must go somewhere and that these channels are physiologically available for its release.

2. The Ethological Tradition

The founders of ethology saw themselves as the direct heirs of Darwin’s work on mental evolution (Lorenz 1965). Their account of the evolution of emotion retains Darwin’s principles, but reinterprets them to fit the theory of evolution as it emerged in the 1930s in the ‘modern synthesis’ of Darwinism and Mendelian genetics. The principle of serviceable associated habits is transformed into the ethological concepts of ‘ritualisation’ and ‘derived activity’ (Tinbergen 1952). Derived activities are behaviors that originally evolved for one purpose but were later selected for another purpose. Ritualized behaviors are derived activities that originally evolved to fulfill some practical function but which were later selected to function as signals. Thus, although piloerection in fear and rage does not make a human being appear larger to an opponent, it does communicate his or her emotional state. Derived activities require a special pattern of evolutionary explanation. They cannot be understood purely in terms of the function they currently perform and the selection pressures that currently maintain them in the population. This is particularly obvious in the case of signals. Piloerection is not intrinsically better as a signal of fear than smiling or laughing. This particular behavior was selected as a signal only because it was already associated with certain emotional states in the distant past. It was associated with those states, not because it was a signal, but because it made the animal appear larger.

The concept of ritualization allowed ethology to reconstruct Darwin’s principle of serviceable associated habits whilst avoiding his commitment to the inheritance of acquired characteristics. Darwin’s descriptions of the psychological rewards that led to the reinforcement of emotional behaviors are equally plausible as descriptions of the original selective advantage of those behaviors. Darwin’s other two principles are equally open to reinterpretation. The principle of antithesis is explained by the selective value of unambiguous signals. It is as important for a dog to signal that it wants to avoid conflict as for it to signal aggression. Hence there can be selection of behaviors merely because they look different from the behaviors that signal aggression. The principle of direct action was transformed into the ethological concept of a displacement activity. Early ethologists shared Darwin’s view that instinctive motivations cause a build up of mental energy that must be released in some behavior or other. An example commonly given is that of an angry cat that is unwilling to attack and begins to wash itself. Niko Tinbergen remarks: ‘I think it is probable that displacements do serve a function as outlets, through a safety valve, of dangerous surplus impulses’ (Tinbergen 1952, p. 23). This wholesale reinterpretation of Darwin’s three principles works so smoothly and allows the retention of so much of the detail of Darwin’s work that the early ethologists seem almost unaware of the differences between Darwin’s theory and their own (Lorenz 1965).

3. The Affect Program Theory Of Basic Emotions

Darwin’s detailed accounts of human facial expressions were confirmed and extended during the 1960s and early 1970s and many of his suggested homologies between human and primate facial expressions were confirmed. In addition, it became generally accepted that some emotional expressions, the so-called ‘basic emotions,’ are found in all cultures and have an evolutionary history at least as long as the history of the human species (Ekman 1973). The basic emotions are usually referred to as fear, anger, disgust, contempt, joy, sadness, and surprise, although in normal usage each of these words has a much wider meaning. During the same period, the hydraulic metaphors that the ethologists had used to describe psychological processes were replaced by a computational model of emotion. Each basic emotion corresponds to an ‘affect program’ stored somewhere in the brain. When activated, this program coordinates a complex of actions that includes facial expression, autonomic nervous system changes, expressive vocal changes, and muscular–skeletal responses such as flinching or orienting. The concept of an affect program inherits many of the features of the earlier ethological concept of a fixed action pattern. Both concepts suggest that certain apparently complex behaviors are, in reality, atomic units of behavior that unfold in the same, stereotyped sequence whenever they are triggered. The affect programs are controlled by an ‘automatic appraisal mechanism.’ This is a specialized neural system that applies its own distinctive rules for stimulus evaluation to a limited set of data derived from the earliest stages of the processing of perceptual information. Considered together, the appraisal mechanisms and affect programs form a cognitive module in the sense favored by more recent evolutionary psychologists (Barkow et al. 1992).

The affect program theory retains two distinctive features of the earlier, ethological model of emotions. First, emotional behaviors are the inevitable and involuntary accompaniment to an underlying emotional state and as such are reliable signals of that state. Second, deliberate attempts to disguise emotions are subject to ‘leakage’ from the operation of the involuntary emotional response. Voluntary attempts to suppress emotional behavior can only operate by simultaneously using the muscles involved in the expression for some other purpose. They cannot interfere with the actual operation of the emotion module.

The affect program theory was accompanied by a distinctive theory of the evolution of the emotion system. The system was interpreted as an ancient form of cognition that had originally operated on its own and had later been supplemented by higher cognitive functions. This view was supported by MacLean’s theory of the ‘triune brain,’ according to which the emotions are located in the ‘paleomammalian’ portions of the brain while higher cognitive functions are realized in newer, ‘neomammalian’ structures (MacLean 1952). The survival of these ancient forms of behavior control in primates was explained by their value as fail-safe responses ensuring that vital behaviors are performed whenever necessary even if that means they are performed too often. This view of the emotion system as a collection of primitive but reliable fail-safe mechanisms remains influential (Panksepp 1998).

4. Sociobiology And The Emotions

Sociobiology brought a new perspective to bear on the evolution of emotion in the 1970s and 1980s. It also moved the focus of investigation from the basic emotions to the moral and quasi-moral emotions involved in human social interaction. Emotions such as trust, loyalty, guilt, and shame play an obvious role in mediating the competitive social interactions that were the focus of most research in human sociobiology. Numerous sociobiologists made brief comments to the effect that moral emotions must have evolved as psychological mechanisms to implement evolutionary stable strategies of social interaction (Weinrich 1980). Robert A. Frank suggested that the moral emotions evolved as solutions to ‘commitment problems’ (Frank 1988). A commitment problem arises when the winning strategy in an evolutionary interaction involves making a binding but conditional commitment to do something that would be against one’s own interests if the condition were ever met. If such a commitment is to be credible, some special mechanism is needed which would cause the organism to act against its own interests. Frank suggests that emotions such as rage and vengefulness evolved to allow organisms to engage in credible deterrence, threatening self-destructive aggression to deter a more powerful aggressor. Conversely, emotions such as love and guilt evolved to allow organisms to engage in reciprocal altruism in situations where no retaliation is possible if one partner fails to reciprocate.

Sociobiologists criticized ethology for its lack of a theoretical framework with which to predict how humans would behave, accusing it of being little more than descriptive natural history (Barash 1979, Barkow 1979). In contrast, sociobiology seemed to make strong predictions that clashed with some aspects of the affect program theory of basic emotions. From a sociobiological perspective it makes no sense for organisms to possess involuntary expressive behavior. The application of evolutionary game theory to emotional behavior predicts that this behavior will be designed to manipulate the expectations of other organisms rather than to ‘express’ emotional states transparently. This theoretical argument has been used by some to reject the affect program view of basic emotions. Alan Fridlund has argued that emotional behavior should be regarded as a paralanguage of social signals whose production depends at least as much on an organism’s social context as on its emotional state (Fridlund 1994). Fridlund and other paralanguage theorists have documented audience effects on the production of the basic emotions and have argued that this is inconsistent with the affect program theory. They have also tried to show that the classic facial expressions of emotion are not strongly correlated with underlying emotional state and that people rely more on context than on behavior in attributing emotions to others (Russell and Fernandez-Dols 1997). It is unclear, however, that this data contradicts the predictions of the affect program theory. Signaling behavior exhibits audience effects in many organisms, such as domestic chickens, in which that behavior is presumably part of a highly stereo- typed behavior sequence controlled by a relatively simple cognitive mechanism.

Mark Hauser has suggested that Fridlund’s arguments bear on questions about the biological function of emotional behavior whilst the affect program model is concerned with the mechanisms that produce that behavior (Hauser 1996, pp. 495–6). In some places, however, Fridlund does seem to be discussing the nature of the underlying emotional processes and not merely their biological function. He argues that since emotions are signals and are produced because of the impact they will have on other organisms, a particular emotion defined behaviorally need not correspond to any particular motivational state (emotion) of the organism producing it.

5. Evolutionary Psychology And The Emotions

The evolutionary psychology movement of the late 1980s and 1990s has been less inclined than sociobiology to question the accepted view of basic emotions. The evolutionary psychologists believe that the mind as a whole is made up of modules that operate independently of one another. Like the emotion system, these modules operate on specific kinds of data using algorithms that differ from those used by other modules. Hence, evolutionary psychology endorses the affect program theory of basic emotions, but wants to go further, both by adding to the complexity of the known affect programs and by finding modular mechanisms underlying other emotional behaviors. John Tooby and Leda Cosmides suggest a number of cognitive and behavioral systems that they would expect to receive output from the affect programs, in addition to those currently known to receive such output (Tooby and Cosmides 1990). They also suggest that the affect programs will be elicited by simple, perceptual stimuli that have played a recurrent role in human evolutionary history. Current empirical research suggests, however, that few simple perceptual stimuli elicit affect programs in the absence of any individual experience of those stimuli. Most evolutionary influences on sensitivity to simple perceptual stimuli seem to take the form of learning preparedness: the relative ease with which one association is acquired rather than another. Genuine pan-cultural antecedents of emotion seem to be relatively abstract states of affairs having to do with the significance of a situation for the organism and requiring local knowledge to translate them into perceptible features of the stimulus situation (Ekman and Davidson 1994, pp. 144–77).

The leading evolutionary psychologist, David Buss, has argued for the existence of a module for sexual jealousy, one of the additional modules predicted by Tooby and Cosmides. Buss argues that sexual jealousy has simple perceptual elicitors such as unusual scents, changed sexual behavior, excessive eye contact, and violation of rules governing personal space. ‘These signals alert us to the possibility of infidelity, since they have been statistically linked with relationship loss over the long course of human evolutionary history’ (Buss 2000, p. 45). The jealousy module uses specialpurpose algorithms and, like the basic emotions, it functions as a fail-safe mechanism: ‘failing to detect an infidelity was more costly than mistakenly accusing an innocent partner of betrayal. Evolution, as a consequence, forged a hypersensitive defense system, designed to sound the alarm not just when an infidelity has been discovered, but also when the circumstances make it slightly more likely’ (Buss 2000, p. 224). When triggered, the module produces various forms of violence against female sexual partners, including, under certain environmental conditions, murder. A noticeable contrast between these recent theories and more traditional accounts of the evolution of emotion is the absence of the idea that emotions represent a more primitive form of behavioral control that can be contrasted to rational, planned action. The emotions are seen as just another cognitive module reflecting details of the environment of evolutionary adaptedness.

6. Conclusion

Current theories of the evolution of emotion all stem from the intellectual lineage stretching back to Darwin himself. There are a number of disagreements between current researchers, however. These include the number of separate, evolved emotions, the nature of the stimuli that produce evolved emotions, and a cluster of issues about the evolutionary function of emotional behaviors and their relationship to underlying emotional states, issues which are often discussed in terms of whether emotional behaviors should be primarily regarded as expressions or as signals.

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