Motivation and emotion/Book/2018/Evolutionary theory of emotion

Overview
Over the course of evolution, "universal human predicaments" have recurred numerous times in which our ancestors made selective choices to ensure both their physical and reproductive survival. Whichever choice they made in the face of threats or opportunity was guided by situational cues, physiological states and appraisal of their situation; through a selective process over long periods of time, physiological and behavioural responses to certain cues have become innate adaptations in humans, or "typical of the species" (Cosmides & Tooby, 1990; Ekman, 1992, p. 171; Nesse, 1990). This perspective describes emotion as those innate adaptations, whether they were good or bad, emotions prompted us in a direction which "in the course of evolution has done better than other solutions in recurring circumstances that are relevant to our goals" (Cosmides & Tooby, 1990; Ekman, 1992, p. 171). Emotions additionally send signals to those around us about our own state, about antecedent events or about our most probable behavioural response, and recognition of these emotions is innate in all humans (Ekman, 1992; Tracy, 2014).



Early evolutionary theories
As described by Nesse, an evolutionary approach defines emotion as "specialised modes of operation shared by natural selection to adjust the physiological, psychological, and behavioral parameters of the organism in ways that increase its capacity and tendency to respond adaptively to the threats and opportunities characteristic of specific kinds of situations" (1990, p. 268). Nesse argues that this definition points out two important factors: distinct emotions have evolved for distinct adaptations, and that to understand how an emotion works we must understand its adaptive function. Therefore, to be able to define emotions and their mechanisms, we must be able to describe their corresponding adaptive challenges. Below are a few theories that attempt to explain emotion through an evolutionary lens.

The James-Lange theory of emotion
The James-Lange Theory was one of the first biological theories of emotion which emphasised the role of the autonomic nervous system in emotion. In short, it explains that a stimulus (an exciting object/animal/person/event) and physiological reaction (Immediate reflexes and primary feeling) come before an emotional response (secondary feeling), and that the subjective feeling of emotion is a result of said physiological changes and excitement (Fehr & Stern, 1970). Early studies found support for this theory, Hohmann (1966), for example, found that people who had injury to their upper, middle and lower spinal cord had decreases in their feeling of emotion, particularly fear and anger. This study showed that interference with the second part of the theoretical sequence (physiological reaction/ excitement) had measurable affects on the last part of the sequence (subjective emotional feeling). Although there was some early support, the theory is not without limitations. Evidence has been found of feelings of emotion existing even with an injury to the central or autonomic nervous system, additionally there is criticism of the theory's simplicity in its description of signals to cortical areas and general lack of knowledge concerning anatomy (Cannon, 1931; Fehr & Stern, 1970; Hohmann, 1966).

Darwin's principles
Darwin's 'The expression of emotion in man and animals' essentially paved the way for evolutionary theory of emotion, in his book he writes about three principles which he believed were associated with emotional expression (Darwin, 1872) :


 * Principle of serviceable associated habits - These are what Darwin regarded as intentional actions carried out under the influence of an emotion.
 * Principle of antithesis - Darwin proposed that each emotion has an opposite and that the movements associated with those emotions contrasted each other, for example, smiling when happy and frowning when sad (Weisfeld & Goetz, 2013).
 * Principle of expressive habits - This principle describes manifestations of the autonomic nervous system (ANS) associated with expression of emotion.

Although these principles aren't heavily used in today's vernacular, this work stimulated extensive research and was the catalyst for influential theories of emotions such as Ekman's basic emotions (Ekman, 1992; Weisfeld & Goetz, 2013).

Cosmides and Tooby's theory
Cosmides and Tooby approach evolutionary theory of emotion in terms of computational programs and algorithms which acknowledge that biological and cognitive elements of behaviour are influenced and mediated by emotion (Cosmides & Tooby, 2000; Tooby & Cosmides, 1990). They posit that present human biology, behaviour, and cognitive ability are essentially information-processing programs with specialised functions that were selected for in our evolutionary past. These programs, at times, can be conflicting; for example, sleep and flight from a predator are two programs which can create incompatible outcomes in the form of actions and/or physiological states. Emotions are described as 'super-ordinate programs', programs which can override or deactivate one over another in order to coordinate functional action; this adaptation evolved as it assisted in solving certain recurring problems in our ancestral past to further our chances of survival and reproductive success. Using their theory in the example of sleep and escaping a predator, the emotion of fear as a super-ordinate program is theorised to coordinate action while functions and programs associated with sleep would be deactivated to allow fleeing (Cosmides & Tooby, 2000).

"Fighting, falling in love, escaping predators, confronting sexual infidelity, and so on, each recurred innumerable times in evolutionary history, and each requires that a certain subset of the psyche’s behavior-regulating algorithms function together in a particular way to guide behaviour adaptively through that type of situation. This structured functioning together of mechanisms is a mode of operation for the psyche, and can be meaningfully interpreted as an emotional state" (Tooby, 1985).

Cosmides and Tooby suggest that any biological processes which have been used to ensure survival or further reproductive success, should have come to be partially if not entirely 'governed by an emotional state'; they also outlined several criteria to assess the environmental antecedents and mechanisms in which an emotional adaptation was selected for (1990, p.412; see Cosmides & Tooby, 1990, p.411 ).

Cannon-Bard theory
This theory proposes that emotional experience stems from activity in the thalamic region, it is here that sensory information is received, organised and redistributed to appropriate cortices for emotional response mechanisms to be mobilised; this activity can be mediated or blocked by the neo-cortex, an evolutionarily more recent brain structure (Dalgleish, 2004; Newman, 1936). It was found that when removing parts of the cortex in cats certain behaviours seemed to be uninhibited and the animals would frequently lash out in anger even when unprovoked, a phenomena Cannon called 'sham rage' (Cannon, 1931; Dalgleish, 2004; Dror, 2014). Additionally, when the thalamus was removed, these emotions were not exhibited at all (Cannon, 1931; Newman; 1936). Despite its early criticisms (see Newman, Perkins, & Wheeler, 1930) this theory provoked much research into what is now known as the limbic system's integral role in emotion (Dalgleish, 2004).

The role of cortical and sub-cortical brain structures in emotion


The cortical brain describes the outer most layer of the brain, it is believed to be the most recent in evolutionary history and possesses systems for higher cognitive abilities in humans (Dalgleish, 2004). The sub-cortical brain, also known as the limbic system, consists of a smaller collection of structures which communicate with the cortical brain for numerous different processes (Phelps & LeDoux, 2005). The dramatic consequences of early experiments with removal of certain brain components in animals sparked substantial amounts of research into the biological side of emotional adaptations. A famous example is Kluver and Bucy's monkeys (1939); numerous strange behaviours were observed in primates that had their temporal lobes removed (including amygdala and hippocampal formation), such as a tendency to approach any animate and inanimate object with lack of emotional response (such as avoidance or excitement). Briefly described below are few structures from both cortices which have been implicated in the expression of emotional behaviour, learning and memory.

Important sub-cortical structures in emotion

 * The amygdala - Like many brain structures, it has been found to be involved in many complex processes which further involve communication and/or mobilisation of other brain structures, both cortical and sub-cortical (Adolphs, 1999; Phelps & LeDoux, 2005).  In particular, the amygdala has been found to play a vital role in emotional learning, memory, facial recognition, and mobilising emotional responses. Following appraisals of threatening situations, the amygdala is able to communicate with other cortical areas to not only elicit a defence response, but also help to store the memory associating threat with a particular stimuli (an effective method to avoid certain people or objects again) (Phelps & LeDoux, 2005).

"Such emotional reactions would include autonomic, endocrine and somatomotor changes in the body, as well as neurophysiological and neuromodulatory changes in brain function" (Adolphs, 1999).


 * The hippocampus - It has been established that the hippocampus is important for contextual fear conditioning, a study by LaBar, LeDoux, Spencer, and Phelps found that participants with amygdala damage who had an intact hippocampus did not experience the feeling of fear or associated physiological states but were still able to report events of conditioning procedures (LaBar, LeDoux, Spencer, & Phelps, 1995; Phelps & LeDoux, 2005).


 * Thalamus - It is suggested that fear conditioning has its basis in the thalamus as it sends visual, auditory and somatosensory information to the amygdala, whereby activation of an emotional response may or may not occur; without the input of this information, fear associations may not be as readily made (Gallagher, & Chiba, 1996).

Important cortical structures that communicate with the sub-cortical brain

 * Prefrontal cortex - works with the amygdala to process the punishment or reward of salient emotional stimuli (Adolphs, 1999).
 * Ventromedial prefrontal cortex - Some studies suggest this structure is important in integrating emotional experience with complex decision making, such as those which would be made in social settings ( Adolphs, 1999). The ventromedial cortex has also been found, alongside other frontal lobes, to connect perceived stimuli with emotional and social meaning; it has been observed that people with damage to this area display a complex set of irregularities, including lack of empathy, certain elements of emotional knowledge, general abnormal response to emotional stimuli, and impaired reasoning in social scenarios (Adolphs, 1999).

The triune brain theory
Proposed by neuroscientist Paul Maclean, this theory claims that existing within the human brain (and few modern mammals), is essentially three brains or systems that have each been developed through evolution (Heimer, Trimble, Van Hoesen, & Zahm, 2007). The first system is the reptilian brain, evolutionarily the oldest and is where 'primitve' emotions such as fear and aggression reside; followed by the paleomammalian brain, and finally the neomammalian brain being relatively the most recently developed (Dalgleish, 2004). Each of these systems have their own functions but are able to communicate and "inter-mesh" (Heimer, et al., 2007, p.19). The neomammalian brain possesses higher cognitive abilities such as problem solving and communication between cognition and emotional responses. It is believed that these higher processes are the reason humans don't show as dramatic effects as primates when suffering lesions to sub-cortical regions, they allow us to integrate other social and cognitive information to make decisions (Adolphs, 1999; Kluver & Bucy, 1939).


 * Limitations of this theory: One early criticism of the theory is evidence of 'non-mammalian vertebrates' possessing elements of the limbic system in some form which interrupts the consistency of the theory (Heimer, et al., 2007, p.19). More criticism has come from research into limbic system structures which have found that some structures are involved in higher cognitive functions such as emotional memory, learning, and recognition of emotion in others (Dalgleish, 2004; Gallagher & Chiba, 1996).



Basic emotions and facial recognition
" Emotional experience and the perception of someone else's emotion are distinct processes, but both are part of the emotion's functional output" (Tracy, 2014, p.309).

How do you know if someone is disgusted? This emotion is said to be activated to help the body rapidly retract from or expel unwanted substances, so you might see a person yelling 'yuck!', maybe wrinkle their nose or pull back from a suspicious substance they see on the ground (Levenson, 2014). Facial and verbal expressions act as signals to other members of our species; they let others know our emotional state, events that may have preceded our emotion, and what our next behaviour may be (Ekman, 1992). Sub-cortical structures in our brain, particularly the amygdala, have been found to be essential in this process of being able to recognise threats or problematic situations which should be avoided (Phelps & LeDoux, 2005).

Ekman's basic emotions
Ekman's early theory described six basic emotions believed to be recognisable and innate in all humans, they are distinguishable and separate in their characteristics (what the emotions looks/sounds like), antecedent events (what triggered the emotion), responses (behaviour when feeling the emotion) and physiology (what our ANS does during the occurrence of the emotion) (1999). Ekman believed that these basic emotions help to mobilise the body to deal with intrapersonal and interpersonal encounters in a way that has been beneficial for our ancestors in the past (1992). The term 'basic' was used to indicate the primary function of the emotions as being quick responses to fundamental, or basic, life tasks through means which have been historically adaptive; additionally, the six emotions, anger, fear, disgust, happiness, sadness, and surprise, are described as basic as they have been used to interpret the formation of more complex emotions (Ekman, 1999, 1992).

To distinguish these basic emotions from other affective states, moods, emotional attitudes, and emotional or personality traits, Ekman formed a list of nine features in which an emotion must possess to be considered basic, these can be found in Table 1 (1992).

Levenson (2014) found some evidence of this in a small laboratory experiment in which a participant's heart rate, skin conductivity, and facial expressions were monitored while watching an industrial safety video. It was found that there were coordinated spikes in heart rate and skin conductivity within the first second of the saw accident as well as the first expression of disgust ( p.6). Levenson suggests that bursts of facial expression are associated with periods of intense emotional response, and therefore facial expression is related to the onset as well as the peak of ANS response (2014).

Limitations of this theory? It has been pointed out that the second criteria for basic emotions, 'presence in other primates' should not be necessary as some adaptations exist in only a single species (Buss, 2014). Although Levenson found evidence of a relationship between emotion and specific, coordinated patterns of ANS activity, he indicates that the literature still shows much uncertainty around whether or not specific emotions have a direct relationship with specific autonomic nervous system activities, and whether or not that further predicts the expression of basic emotions (2014). Lastly, it is important to note the influence of social learning in basic emotions, Ekman highlighted the criteria of appraisal as a particular place where social learning has a great impact, for example, a culture that is taught to co-exist with snakes would not have a fearful automatic appraisal of one, consequently, snakes would not qualify as a universal antecedent for fear (1990).



Universality of basic emotions
Some studies, particularly Ekman's early works, have shown that emotional expressions can be interpreted throughout different cultures (Ekman, 1992, 1999). Sauter, Eisner, Ekman, Scott and Smith (2010) found evidence of this when conducting experiments with native European English speakers and a semi-nomadic group in northern Namibia known as the Himba people. In the study, each group listened to a short emotional scenario followed by two non-verbal vocal recordings of either Himba or European voices (i.e., Himba participants heard recordings of European vocalisations and vice versa) conveying a certain emotion. Next, the participants were asked which vocalisation matched the emotional story they heard earlier. Sauter et al. found that the emotions reliably identified by both groups were those considered to be basic emotions (2010).

In contrast, Yan, Andrews, and Young (2016) conducted four experiments in the United Kingdom with samples made up of Chinese and British participants. Over the course of their study, it was consistently found that both groups were reliably able to see the similarity of emotions on the faces of different actors, but that British participants were able to categorise the emotions more reliably. It was also found that Chinese participants were able to better categorise emotions when shown images of Chinese actors simulating emotions; these results are in line with the concept of 'own-group advantage', whereby people are better at recognising emotional expressions in people from their own cultural group (Yan, et al., 2016).

The sub-cortical brain and emotional recognition
The amygdala has been found to be involved heavily in emotional facial recognition, particularly negative emotions, such as fear (Adolphs, 1999). Yip, Leung, Li, and Lee's (2004) study with healthy subjects and subjects who had suffered damage to sub-cortical regions found that the latter participants did much worse than their healthy counterparts when asked to identify vocalisations and photographs of the six basic emotions (specifically fear, disgust, and sadness). Furthermore, Adolphs, Baron-Cohen, & Tranel's study (2002) showed that participants with damage to the amygdala showed a loss of ability to recognise threat in facial expression, and consequently, an abnormally higher level of trustworthiness and willingness to approach those with the most negatively oriented expressions (Adolphs, 1999). In an evolutionary sense, this loss of ability to perceive negative emotions in others and gained willingness to approach anything can have dangerous consequences.

Implications of evolutionary theory on emotion
Although breaking findings have been found in animals, much of this research still needs to be tested with and applied in humans; despite this Phelps & LeDoux (2005) suggest that mental illnesses which stem from maladaptive appraisals of everyday situations can be altered through appropriate coping measures. Maladaptive behaviour can also be influenced and changed by using knowledge of physiological systems involved in such appraisals (Cosmides & Tooby, 1999). Such disorders may include phobias, post-traumatic stress disorder, depression, anxiety, and some emotional disorders; Phelps & LeDoux suggest that informing individuals on how to better interpret situations and reappraise emotional stimuli can have a great impact on how the body responds accordingly (2005).

Conclusion

 * The evolutionary perspective on emotion proposes that emotions are innate adaptations which aid us in decision making and problem solving.
 * Early theories of emotion posited that subjective feeling was a result of a physiological reaction to an exciting stimulus, and that there were three principles of emotional expression.
 * Evidence in physiological systems (such as the ANS) and brain structures (such as the amygdala) shows that the brain is equipped to to recognise and mobilise the body to deal with perceived threats when feeling emotions such as fear or anger.
 * It was proposed that there are six basic emotions, distinguishable in their characteristics, antecedent events, and physiological symptoms; evidence has been found to support that these emotions are innate and recognisable in all humans, although there is also some evidence of 'own-group advantage' whereby a person better perceives the emotions of those in their own cultural group.
 * Research suggests that applications of evolutionary theory of emotion point towards areas that deal with disorders where individuals tend to make maladaptive appraisals of their situations, and therefore activating adaptive systems at inappropriate times such as anxiety, phobias, and depression.