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Scientific American

Wag the Dog

published April 2008 | comments (6)
Emotions are as much a product of our evolutionary
heritage as they are our environmental circumstances
magazine cover

The next time you come face to face with a dog wagging its tail, you can make a quick determination on whether to reach out and pet it or step back in deference: check the tail-wag bias. If the wagging tail leans to the dog’s right, you’re safe; if the tail leans to the dog’s left, don’t move.

This tail-wagging bias was documented in a 2007 article in the journal Current Biology by Italian neuroscientist Giorgio Vallortigara and his veterinarian colleagues at the University of Bari. In an experiment, 30 mixed-breed dogs were each placed in a cage equipped with cameras that measured the asymmetrical bias (left or right) of tail wagging while the pooches were exposed to four stimuli: their owner, an unfamiliar human, a cat and an unfamiliar dominant dog. Owners elicited a strong right bias in tail wagging, and unfamiliar humans and the cat triggered a slight right bias. But the unfamiliar dominant dog (a large Belgian Shepherd Malinois) elicited a strong left bias in tail wagging. Why?

According to the researchers, because the left brain controls the right side of the body, and vice versa, the nerve signals cross the midline of the body and cause the dog’s tail to wag more to the right when its left brain is experiencing a positive emotion. This left-right distinction may be explained by the fact that birds, fish and frogs show left-brain/right-brain differences in approach-avoidance behavior, with the left brain associated with positive approach feelings and the right brain associated with negative avoidance feelings. Closer to evolutionary home, when chimpanzees are experiencing negative emotions, they tend to scratch themselves on the left side of their bodies, and left-handed chimps, whose right brain is dominant, tend to be more fearful of novel stimuli than right-handed chimps.

In humans as well, experiments have revealed that the left brain is associated with positive emotions such as love, attachment, bonding and safety. For example, electroencephalogram (EEG) studies of the brains of subjects who report positive emotions or are shown a funny video clip experience an increase in activity in the left frontal cortex, whereas reports of negative emotions and unpleasant video clips coincide with an increase in activity in the right frontal cortex. In addition, brain scans of subjects who are viewing a photograph of a cute baby show increased activity in the same left frontal cortex area; subjects looking at a photograph of a grotesquely deformed baby show increased activity in the same right frontal cortex area. Finally, bombarding the left frontal cortex of the brain with a strong magnetic field elicits a positive mood in human subjects, and the reverse elicits a negative mood.

Why would the brain show such differences in neural networks associated with emotions? Employing evolutionary theory, I would like to suggest that emotions interact with our cognitive thought processes to guide our behaviors toward the goal of survival and reproduction. University of Southern California neuroscientist Antonio R. Damasio, for example, has demonstrated the vital role that emotions play in decision making. At low levels of stimulation, emotions appear to have an advisory role, interacting with the more reason-oriented cortical regions of the brain. At medium levels of stimulation, conflicts can arise between these cortical reason centers and the brain’s deeper and evolutionarily older emotion centers. At high levels of stimulation, emotions can so overrun cortical cognitive processes that people can no longer reason their way to a decision and report feeling “out of control.” But why should we have evolved emotions at all?

Emotions are evolutionary proxies for getting us to act in ways that lead to an increase in reproductive success. If we think of the feeling of hunger as a very basic emotion, for example, a little bit of hunger may be perceived as pleasant, motivating us to seek and find food, whereas too much hunger becomes an unpleasant emotion when it goes unmet. In this homeostatic model, emotions act as a feedback mechanism to alert the brain when the body is out of balance. Positive emotions help us build enduring personal resources, such as problem-solving skills, coordination and social resources. Negative emotions, in contrast, help to protect us. Fear causes us to pull back and retreat from risks. Disgust directs us to push out and expel that which is bad for us. Anger leads us to fight back or to signal displeasure at the violation of a social agreement. Jealousy leads us to guard our mates against intruders in pair-bonded relationships.

Such studies indicate that often the evolutionary tail wags the emotional dog.

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6 Comments to “Wag the Dog”

  1. Dave Winslow Says:

    Great article, emotions have long been underestimated, under-respected. We were once swinging in the trees, or something like that, without language, and without a whole lot of developed ideas. Of course emotions drove our behavior, what else would have done so? Thanks

  2. RV Says:

    Interesting…perhaps this is why I (right-handed) have trouble seeing eye-to eye with my left-handed wife on things that ellicit strong emotional responses. Debates are very heated when things get emotional.

  3. Albert Fonda Says:

    Interesting indeed. But, didn’t SciAm swap the colors in the April issue? The dog on the right seems to be wagging to its right, which should be “safe” (left brain, positive emotion). However, for that dog the background color is red; for the other dog, it’s green. Which should it be?

  4. Peter B. Todd Says:

    Perhaps Dr Shermer has unwittingly succeeded in demolishing the epistemological foundations of cognitive behaviour therapy with his thesis about the evolutionary significance of emotions. He certainly seems to have ignored the implications of recent neuropsychoanalytic contributions to the scientific understanding of non-rational, unconscious ego-defences and affects. For instance, those of Turnbull & Solms (2007)as well as those in the vast, published, peer-reviewed psychosomatic research literature.

    The problem for Dr Shermer’s position, I believe, is rooted in his conscious or unconscious investment in neural reductionism – a radical materialism which leaves little causal room for mentality in the brain-body-environment equation. Such mindless materialism would prevail if the empirical study of subjective experience had not already provided robust and useful scientific predictions.

    Even such sophisticated techniques as functional magnetic resonance imaging(fMRI)do not permit the prediction of phenomenology. They only reveal the neural correlates of subjective experience and of unconscious mental processes, including defences and the emotions of which Dr Shermer writes. As for the behaviourism implicit in Dr Shermer’s remarks on “approach” and “avoidance” emotions, neuroscientist Karl Pribram (2004) made the pithy remark that “the more reflex the reflex, the less does mind accompany it”!

    The “three worlds” described by Popper & Eccles (1990)of mind, brain and culture interact in a feedback loop so that mid or consciousness program the brain to evolve culture which in turn stimulates mental development. The objection that the Popper/Eccles position violates the conservation of energy principle has been addressed by a number of authors including Hiley (2005) in the journal “Mind & Matter” in a provocative paper on mind as active information.

    Thus, a mental achievement such as the mathematical calculus as a cultural product in Popper’s “World 3″ textbooks,stimulates the mental development of physicists and perhaps even some psychologists, like Dr Shermer.

    Dr Shermer’s treatment leaves mind as much the same anomaly for science, including evolutionary psychology, as it was for Darwin’s contemporary Wallace. Neural reductionism does not provide much enlightenment into the nature of the mind-brain interface or into the debate over such phenomena as language which occurred between behaviourist Basil Skinner and linguist Noam Chomsky.

    Dr Shermer’s own sceptical attitude might have led one to expect a more sophisticated critique of the status of the mental than the one conveyed in his comments on “wagging the tail”.

  5. Lawrence Trevanion Says:

    Hi Michael,
    I’ve encountered Peter B. Todd’s remarks at . My reply refers to comments of yours so I have sent it to you also in case you are interested.
    It seems to me that for all Todd’s supposed mastery of isms and ologies and, of course, quantum mechanics, he doesn’t understand Berkeley’s dilemma that sits at the heart of his conceptualization.
    Briefly, if perceptions (items of consciousness) exist then everything we know about is accounted for – experience is just a play of existent perceptions and nothing more. The leap from perceptions to the notion that perceptions are perceptions of something is needless. The fact that this has absurd consequences, not least that it denies the existence of the real and leaves us unable to deduce that there are other minds, certainly suggests that Berkeley’s view is false. But this does not entitle us to just ignore the point. Ignoring the point just leaves us with the mind body problem – the unanswered relationship between experience and what we take the experience to be an experience of.
    Berkeley’s proposition is that experience can be understood in terms of perceptions that exist in the mind. But this view does not comprehend the real. And it subverts the notion of perception because perceptions are regarded as existent in their own right rather than perceptions of something.
    This problem can be solved by proposing that experience is what an object perceives thus integrating the concepts of experience, perception and real. A critical consequence of this is that, when I say ‘I see (perceive) X’ for example, I mean only that X exists and not that my seeing of X also exists i.e. ‘I see X’ does not mean ‘My seeing of X exists’. Experience understood in this way does not produce the dual existences of the mind body problem.
    The critical difficulty in sustaining this point of view relates to how we understand our own personal perception. In interpreting our experience as experience of the real we can treat all other persons as exclusively real – real world, real phenomena that mediate perception, real mechanisms of perception and real responses. The neurologist can regard a human and its brain entirely as an object – there is no inconsistency in principle and nothing is obviously missing from this understanding. But how are we to treat the relationship between our own personal experience and the real? Well that has already been stated – we perceive the real, or to state it in treacherous abstract terms, our experience is (in part) the perception of the real. We become necessarily confused by an incomprehensible self-referential tangle if we attempt to consider our own perception as an entity in that real. (Treating our experience as an entity in the real is equivalent to Berkeley’s false proposition that perceptions exist.)
    This goes to the heart of Todd’s question about the correspondence between phenomenology and brain mechanism. It is the basis for his criticism of Michael Shermer’s comment “I would like to suggest that emotions interact with our cognitive thought processes.” (Available on line)
    I too think there is a problem with Michael’s comment but, needless to say, my criticism is different to Todd’s. There are not pieces of (existent) emotion following brains around and influencing their mechanism. There are not pieces of our perception of the real following brains around, mimicking the brain’s sensing of the real and influencing the body to react in much the same way that the brain appears to do. Shermer’s question shouldn’t be ‘Why do we have emotions?’ (implying existent perceptions) but rather, “Why do we perceive emotions?”, a question that is no different in principle to asking ‘Why do we perceive the real?’. “I perceive an emotion’ can be treated in the same way as ‘I perceive a mouse’ and both can be explicated in terms of the real. Consequently, looking at the survival value of perceiving emotions seems sensible to me.
    The question as to why we perceive X in a conscious rather than an unconscious way is interesting. A handy tip for making sense of all such problems is to consider them in terms of someone else as an object (so as to avoid the 1st person problem of treating our perceiving of the real as an entity in the real that we perceive). Our answer will, of course, be it in terms of the real. In this case we ask – why would a perceiver perceive X and not be able to report or remember the fact?
    Reporting is about recognition. This is easy to observe where people specialize. The memory and reporting of X-ray scans or complex music etc is very different in different people or in the same person at different times in their life. A person visually scanning for a lost object is perceiving a great deal but much of the scanning does not culminate in identifying anything and there is, in any case, no value in reporting the scan in laborious detail – it would be a waste of time attempting to do so.
    We do not report reflexes until after the event, presumably because an urgent response is required and memory and reporting are a secondary priority. Rapid responses in sport similarly do not require memory and language and are no doubt inhibited by them on occasion.
    A great deal of the brain’s interaction with the rest of the body is not remembered or reported presumably (in evolutionary terms) because there is no effective action the organism as a whole can take as a result of that information. Where effective action by the whole organism is required this can lead to memories/thoughts/feelings being perceived as, for example, in the experience of thirst and hunger. It needs hardly to be argued that an organism’s motivation need not be available for reporting by the organism itself which means that deliberate choice is a subset of an organism’s conduct – we may choose to hold our breath but not for long. Interestingly, humans are driven by a deep desire to have sex rather than to have children yet they nevertheless then become effective parents.
    It makes sense to say that we think and remember when we are asleep, the results of which are available for reporting when we wake up. This observation is not so different to the observation that we perceive thoughts but perceive very little imagined language prior to doing so i.e. the cause and manner of the ‘appearance’ of thoughts can be explored in terms of the mechanisms of an object that perceives (whereas the notion they arise from the operations of the conscious mind is obtuse). There is no value in a perceiving object perceiving its mechanisms of perception and ultimately it can’t.
    These are the sorts of issues implicated by the distinction between different types of perception.
    A sleep walker can report what they perceive at the time and so the critical issue in this case seems to be some kind of memory (which is a dilemma for consciousness theorists because it raises the possibility that someone could be conscious without knowing it).
    As a whimsical conclusion I offer Todd the thought that relating consciousness to quantum mechanics is the other end of the scale to relating the stars to one’s person. (I hereby claim intellectual property right over quantology horoscopes.)

  6. Maria Says:

    yay! ur right