In my last post I gave a brief description of one of the key mechanisms that Charles Darwin proposed drove the evolutionary process – natural selection. To recap briefly, natural selection is the preservation of phenotypes that are advantageous to individual organisms in what Darwin termed the “struggle for existence” amongst organisms. I noted that phenotypes can be any of an organism’s observable characteristics – some feature of its anatomy, physiology or behaviour. Selection for behaviours is the realm of evolutionary psychology. Generally speaking, evolutionary psychology refers to any attempt to apply evolutionary theory to the study of psychology. However, over the last 20 years or so, the term evolutionary psychology has become synonymous with a particular set of theoretical assumptions put forward by a group of researchers, the most prominent of who include the anthropologist John Tooby and the psychologists Leda Cosmides and David Buss (Buller, 2005). I’ll go into a bit more detail about these theoretical assumptions a little later.
I also noted in my description of natural selection that there must be genes at least partially responsible for each of the variant phenotypes, which parents transmit to their offspring during reproduction. It has been demonstrated quite conclusively in countless studies that genes, as well as experience, make a contribution to our behaviour and our cognition, or mental processing. This makes perfect sense because genes help determine the structure and function of the brain. One simply needs to open any introductory level psychology textbook to see that this is the case. For example, children of one or both parents with schizophrenia, a devastating psychiatric disorder that may involve disturbances in thinking (delusions), perception (hallucinations), emotions and behaviour, are at greater risk of developing the disorder themselves than children of non-affected parents. This is true even in cases where the children have been adopted at birth and raised by non-affected adoptive parents, so genes probably play some role in the increased risk for developing the disorder (Nairne, 2006).
Notice that I stressed the point that experience, or environmental factors also make a contribution. I do not want the idea that genes make a contribution to our behaviour and cognition to be confused with genetic determinism, the idea that these traits are determined entirely by genetics. The environment will always play some role!
In my last post I suggested that humans have a strong tendency to develop a fear of snakes. This does not mean, of course, that all humans have a fear of snakes. When discussing the causes of specific phobias (irrational fear of a specific object or situation), Barlow & Durand (2002) note that several things have to occur for a person to develop a phobia. While there is evidence that our brains seem to be “pre-wired” by our genes to associate fear with certain objects and situations, such as snakes and spiders (that is, we seem to be able to make the association more easily than say with live electrical wires, which are also potentially dangerous - see Footnote below), some kind of traumatic conditioning (or learning) experience is still generally necessary. This experience need not be a direct traumatic encounter with a snake or spider, but could also involve observing someone else experiencing severe fear in response to a snake or spider, or even, in some circumstances, being told about a potential threat. If the "purpose" of fear is to increase the chances of survival by avoiding certain objects or situations it makes sense that this emotion can develop without needing to face any danger directly. For example, a child who has a mother who becomes extremely anxious whenever she sees a spider may themselves develop an anxiety around spiders. Barlow & Durand (2002) mention a case of a woman with a severe snake phobia who had never encountered a snake in her life but had been warned repeatedly when growing up about the danger of snakes in high grass. She was encouraged to wear high rubber boots to guard against the threat – and did so even when walking down the street.
Another "risk factor" for the development of a phobia is the tendency to get anxious about future contact with the feared object or future occurrence of the feared situation (Barlow & Durand, 2002). Such a tendency would more than likely be the result of genetic and early environmental influences combining to produce an anxious, or neurotic, character. While not all fear may be considered irrational or interfere with an individual’s ability to live a normal life, and therefore be considered a phobia, Barlow and Durand's (2002) model gives us a sense of how experience and genetics/biology can both contribute to the development of behaviour and cognition.
Footnote: This is an interesting point and will be touched upon again when I discuss the theoretical assumptions that dominate the field of evolutionary psychology.
References
Barlow, D. H., & Durand, V. M. (2002). Abnormal psychology: An integrative approach (3rd ed.). Belmont, CA: Wadsworth.
Buller, D. J. (2005). Adapting minds: Evolutionary psychology and the persistent quest for human nature. Cambridge, MA: MIT Press.
Nairne, J. S. (2006). Psychology: The adaptive mind (4th ed.). Belmont, CA: Thomson Wadsworth.
Wednesday, August 25, 2010
Friday, August 6, 2010
An Evolutionary View of Emotions
Geez, isn’t it crazy how time gets away from us sometimes? Eight months after my first post, here’s my second! They will get much more frequent, I promise!
Recently I was watching an episode of the British science fiction television series Doctor Who, in which Earth is invaded by a race of cybernetic aliens called Cybermen. According to the leader of these alien invaders the Cybermen were once human but during the cybernetic process “weaknesses” such as emotions had been removed from their brains. This description of emotions as weaknesses by the Cyberleader echoes a belief that is pervasive throughout popular culture, namely that emotions are the products of primitive parts of our brain that interfere with the ability of “higher” parts of the brain to think rationally. Good problem solving requires rational thought – the application of reason, logic, and deduction to arrive at a solution. Emotions only get in the way. But this belief is not just evident in popular culture. Researchers in psychology – the scientific study of behaviour and mental processes - have also tended to contrast “emotionality” with “rationality” (Buss, 2000). An alternative view of emotions that challenges this traditional view is that they are adaptations, traits that have been preserved by natural selection through our species’ evolutionary history because, far from interfering with problem solving, they have provided solutions to adaptive problems that our ancestors have faced.
There are a number of good introductions to Darwinian evolutionary theory. A good introductory web-site on evolutionary theory can be found at: http://evolution.berkeley.edu/ But briefly, according to Darwinian evolutionary theory, natural selection is one of the driving processes of evolution. Natural selection is a very simple mechanism that occurs when three prerequisite conditions are met in a population (Buller, 2005). The first condition is preexisting phenotypic variation. Phenotypes can be any one of an organism’s observable characteristics – some feature of its anatomy, physiology or behaviour. The second condition is that the phenotypic variation must be able to be fairly reliably passed onto the organism’s offspring. In Charles Darwin’s day people were aware that children tend to resemble their parents in certain characteristics, but the actual mechanism by which these characteristics were passed from parent to offspring was unknown. Nowadays we say that there must be genes at least partially responsible for each of the variant phenotypes, which parents transmit to their offspring during reproduction. Finally, the phenotypic variation must be responsible for differences in organisms’ fitness. Fitness is a measure of an organism’s ability to survive and reproduce.
Logically, the number of individuals of any given species cannot keep increasing indefinitely. Eventually, there are going be more individuals than can be supported by the environment due to a limit on available resources such as food. This means that living organisms are typically involved in a “struggle for existence” with other members of their population, competing for limited resources. In addition to trying to gain enough food to survive there is also the problem of not becoming food for something else! Some individuals will differ in slight ways that will give them an advantage in this “struggle for existence” and will give them a better chance of producing offspring than other individuals. A key factor in successfully producing offspring is, of course, surviving long enough to mate. The beneficial variations are more likely to be passed on to future generations. Gradually, these variations will spread throughout the entire population, as those individuals that possess them continue to out-compete the individuals that do not possess them.
An organism’s fitness is largely dependent on how well adapted its characteristics are to the demands or pressures of the environment it inhabits. These “selection pressures” can be thought of as adaptive problems, and some phenotypic variations provide better solutions to these problems than others, thereby improving the chances of survival and reproduction of those organisms that exhibit them. To give an illustrative example, a number of researchers that apply an evolutionary framework to studying human psychology argue that for the majority of our species’ evolutionary history poisonous snakes were a major threat to our ancestors’ survival (e.g. Buss, 2000). Because an encounter with a poisonous snake could prove extremely costly in evolutionary terms (death would have obviously eliminated the possibility of any future reproduction), there must have been a strong “selection pressure” to avoid them. The argument goes that the evolved “solution” to this adaptive problem of avoiding poisonous snakes has been a strong tendency for humans to develop a fear of snakes (Buss, 2000). Fear of snakes is certainly one of the most common fears that humans exhibit (e.g. Agras, Sylvester & Oliveau, 1969, as cited by Barlow & Durand, 2002, and Nairne, 2006). This is just one relatively straightforward example of the emotions-as-adaptations view that I mentioned earlier, just to give a sense of what I was getting at. In a future post I intend to take a much more critical look at a common evolutionary view of another emotion: jealousy.
References
Barlow, D. H., & Durand, V. M. (2002). Abnormal psychology: An integrative approach (3rd ed.). Belmont, CA: Wadsworth.
Buller, D. J. (2005). Adapting minds: Evolutionary psychology and the persistent quest for human nature. Cambridge, MA: MIT Press.
Buss, D. M. (2000). The dangerous passion: Why jealousy is as necessary as love or sex. London: Bloomsbury.
Nairne, J. S. (2006). Psychology: The adaptive mind (4th ed.). Belmont, CA: Thomson Wadsworth.
Recently I was watching an episode of the British science fiction television series Doctor Who, in which Earth is invaded by a race of cybernetic aliens called Cybermen. According to the leader of these alien invaders the Cybermen were once human but during the cybernetic process “weaknesses” such as emotions had been removed from their brains. This description of emotions as weaknesses by the Cyberleader echoes a belief that is pervasive throughout popular culture, namely that emotions are the products of primitive parts of our brain that interfere with the ability of “higher” parts of the brain to think rationally. Good problem solving requires rational thought – the application of reason, logic, and deduction to arrive at a solution. Emotions only get in the way. But this belief is not just evident in popular culture. Researchers in psychology – the scientific study of behaviour and mental processes - have also tended to contrast “emotionality” with “rationality” (Buss, 2000). An alternative view of emotions that challenges this traditional view is that they are adaptations, traits that have been preserved by natural selection through our species’ evolutionary history because, far from interfering with problem solving, they have provided solutions to adaptive problems that our ancestors have faced.
There are a number of good introductions to Darwinian evolutionary theory. A good introductory web-site on evolutionary theory can be found at: http://evolution.berkeley.edu/ But briefly, according to Darwinian evolutionary theory, natural selection is one of the driving processes of evolution. Natural selection is a very simple mechanism that occurs when three prerequisite conditions are met in a population (Buller, 2005). The first condition is preexisting phenotypic variation. Phenotypes can be any one of an organism’s observable characteristics – some feature of its anatomy, physiology or behaviour. The second condition is that the phenotypic variation must be able to be fairly reliably passed onto the organism’s offspring. In Charles Darwin’s day people were aware that children tend to resemble their parents in certain characteristics, but the actual mechanism by which these characteristics were passed from parent to offspring was unknown. Nowadays we say that there must be genes at least partially responsible for each of the variant phenotypes, which parents transmit to their offspring during reproduction. Finally, the phenotypic variation must be responsible for differences in organisms’ fitness. Fitness is a measure of an organism’s ability to survive and reproduce.
Logically, the number of individuals of any given species cannot keep increasing indefinitely. Eventually, there are going be more individuals than can be supported by the environment due to a limit on available resources such as food. This means that living organisms are typically involved in a “struggle for existence” with other members of their population, competing for limited resources. In addition to trying to gain enough food to survive there is also the problem of not becoming food for something else! Some individuals will differ in slight ways that will give them an advantage in this “struggle for existence” and will give them a better chance of producing offspring than other individuals. A key factor in successfully producing offspring is, of course, surviving long enough to mate. The beneficial variations are more likely to be passed on to future generations. Gradually, these variations will spread throughout the entire population, as those individuals that possess them continue to out-compete the individuals that do not possess them.
An organism’s fitness is largely dependent on how well adapted its characteristics are to the demands or pressures of the environment it inhabits. These “selection pressures” can be thought of as adaptive problems, and some phenotypic variations provide better solutions to these problems than others, thereby improving the chances of survival and reproduction of those organisms that exhibit them. To give an illustrative example, a number of researchers that apply an evolutionary framework to studying human psychology argue that for the majority of our species’ evolutionary history poisonous snakes were a major threat to our ancestors’ survival (e.g. Buss, 2000). Because an encounter with a poisonous snake could prove extremely costly in evolutionary terms (death would have obviously eliminated the possibility of any future reproduction), there must have been a strong “selection pressure” to avoid them. The argument goes that the evolved “solution” to this adaptive problem of avoiding poisonous snakes has been a strong tendency for humans to develop a fear of snakes (Buss, 2000). Fear of snakes is certainly one of the most common fears that humans exhibit (e.g. Agras, Sylvester & Oliveau, 1969, as cited by Barlow & Durand, 2002, and Nairne, 2006). This is just one relatively straightforward example of the emotions-as-adaptations view that I mentioned earlier, just to give a sense of what I was getting at. In a future post I intend to take a much more critical look at a common evolutionary view of another emotion: jealousy.
References
Barlow, D. H., & Durand, V. M. (2002). Abnormal psychology: An integrative approach (3rd ed.). Belmont, CA: Wadsworth.
Buller, D. J. (2005). Adapting minds: Evolutionary psychology and the persistent quest for human nature. Cambridge, MA: MIT Press.
Buss, D. M. (2000). The dangerous passion: Why jealousy is as necessary as love or sex. London: Bloomsbury.
Nairne, J. S. (2006). Psychology: The adaptive mind (4th ed.). Belmont, CA: Thomson Wadsworth.
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