Authors: Frank Tallis
Psychology did not resist functionalism. Indeed, within a relatively short period of time psychologists were happy to acknowledge that all mental phenomena could be understood in terms of their purpose – or at least an original purpose which might have become somewhat obscured by more recent evolutionary developments. Nevertheless, functionalism did not change psychology. In textbooks functional considerations rarely developed beyond a superficial but respectful tug of the forelock in Darwin’s direction. Typically a paragraph or two might recognise the functional significance of a mental phenomenon, but thereafter the discussion would more than likely proceed as if Darwin had never been born.
The theory of evolution by natural selection – to give the theory its full name – is based on a few simple tenets. Organisms produce more offspring than can survive and reproduce. Subsequently the organisms that survive tend to be better adapted. Parental characteristics appear in their progeny -thus, better adapted lines will survive and pass on their advantage. A few simple principles, but sufficient, nevertheless, to explain the provenance, appearance, and behaviour of all living things. Moreover, these few simple principles can also explain the emergence of consciousness and the division of the mind into conscious and unconscious parts.
It was work on the survival value of deception – conducted during and after the 1970s – that aroused general interest in the unconscious as an evolutionary concept; however, the unconscious had already been linked with evolutionary theory by those sympathetic to a functional perspective. It was assumed that the appearance ofthe human mind owed much to evolutionary pressures. Moreover, the moiety of conscious and unconscious functions could be understood as a kind of optimal solution to the problem of survival.
Clearly, the ability to reflect on need states, respond to novel stimuli, and make plans are all of considerable value with respect to ensuring survival. They are also functions for which consciousness is ideally suited; however, to execute these functions effectively, consciousness must also be strictly limited. The conscious representation of too much information – for example conflicting needs, unnecessary detail, or too many potential courses of action – would be counterproductive. The organism would be overwhelmed with information and paralysed by indecision. Therefore, all incoming information must be subject to at least a preliminary analysis before being selected for further processing and conscious representation. Moreover, such preliminary analyses must necessarily take place outside of awareness (if consciousness is to remain uncluttered), finally, new skills, which can only be acquired by conscious rehearsal, must be automated as soon as possible; again, this feature of the processing system also serves to keep consciousness available for the performance of its primary functions.
In sum, evolutionary pressures explain why consciousness has arisen, why it is of limited capacity, and why it is complemented by processing activities that take place outside of awareness. The marriage of conscious and unconscious processing capabilities optimises the brain’s capacity to negotiate complex and potentially hostile environments, ensuring survival and subsequent reproductive success.
The processing architecture of the brain has been shaped by evolutionary demands. It is a response to the world – an adaption; however, it is also a record. To peer into the brain is to look backwards in time. The vestiges of our remote ancestry are better preserved in the brain than in any natural history museum.
In the 1960s the neuroscientist Paul MacLean suggested that every human possesses not one brain but three; a reptilian brain, a mammalian brain, and, finally, what might be described as a human brain. The reptilian and mammalian brains recapitulate aspects of our remote evolutionary history, for example the reptilian brain – which is simple, primitive, and swells out at the top of the spine – reflects a stage in our history that pre-dates the development of emotion. The mammalian brain – which is more sophisticated and consists of a large system of linked structures – reflects the evolutionary stage of development during which emotions were established. The most highly developed region of the brain is the cortex – the outer layer that permits human beings to perceive complex stimuli, think through problems, and use language. The cortex is the most recent evolutionary development; however, it is only a few millimetres thick. In physical terms, we are much more lizard and lion than Socrates or Einstein.
Much of what enters awareness is primarily the product of activity in cortical circuits of the brain. The deeper and more central areas of the brain -those reflecting our ancient history – operate beyond awareness. The unconscious foundations of human mental life were laid down in the brain while our very early ancestors were still dodging the tread of dinosaurs.
With respect to ensuring survival, one ofthe most important features ofthe mammalian, unconscious brain, is its potential to generate emotions – of which the most fundamental is probably fear. Contemporary neuroscience suggests that the conscious experience of fear is a relatively minor consequence of activity in a collection of structures that operate largely outside of awareness – the limbic system. It is the limbic system that generates basic emotions. When threatened, an organism equipped with a limbic system will respond very quickly, as a series of automatic ‘programmes’ are engaged. These produce the well-known ‘fight/flight’ response in which adrenalin is released, the heart beats faster, and muscles receive more nutrients owing to increased blood flow. Thus, the chemical environment in the body is altered to facilitate a speedy escape, or if this isn’t possible, an energetic confrontation.
The neuroscientist Joseph Le Doux has identified the specific pathways and brain structures that subserve the fight/flight response. When a frightening stimulus – let’s say a snake – enters the processing system, relevant information is sent down two neural pathways. The first of these pathways transmits information to the visual cortex via a structure called the
thalamus,
which then constructs an image of the snake. This image is merely a descriptive picture – a neutral representation of the snake as an object. Recognition areas then identify this object as a snake by retrieving information stored in long-term memory. Together the image and relevant information produce conscious awareness of the snake as a dangerous animal, and a structure called the
amygdala
is activated. The amygdala then sounds the alarm, thus initiating the fight/flight response.
This pathway, which results in the conscious recognition of dangerous objects, is relatively slow. It is certainly too slow to guarantee survival. By the time it has confirmed that the long, coiled object is indeed a snake, the snake might have already struck. In order to overcome this problem, the brain also possesses a quick and dirty response system. This second pathway links the thalamus directly to the amygdala. A crude representation of the snake (described by Le Doux as ‘almost archetypal’) is transmitted to the amygdala in a matter of milliseconds. Subsequently the fight/flight response is engaged before consciousness is engaged.
Of course, the late arrival of consciousness will provide a more thorough analysis of the ‘long, coiled object’. When this is completed, it might transpire that the amygdala has sounded a false alarm. The snake might turn out to be nothing more than a length of rope, in which case this information is relayed to the amygdala, dampening the fear response. Needless to say, because the fear response is primitive and automatic, the fear programme may still run for a while, keeping the individual in a tense and alert state.
The reason why evolution has equipped the brain with a swift (although not necessarily accurate) processing system is quite straightforward. In the ancestral environment, predators struck quickly. Therefore, it was well worth responding to any potential threat — even if the majority of responses proved to be unnecessary. The cost of failing to respond (or responding slowly after careful, conscious, consideration) was probably death. On the other hand, there were no costs attached to being jittery. In the ancestral environment, it didn’t pay to be cool.
Because the quick and dirty pathway is so important, it operates automatically. Over millions of years natural selection has effectively taken control away from the individual. When in a life-threatening situation the individual cannot be trusted to respond appropriately. He or she might dither and so die. When we startle, we are exhibiting ancient wisdom – the distillation of out species’ learning history.
The conscious and unconscious pathways involved in the generation of fear are clearly complementary; however, with respect to avoiding opportunistic predators, the unconscious pathway is easily the more valuable. This consideration has prompted some theorists investigating the neurophysiology of fear to argue that (at least with respect to avoiding prédation) the role of consciousness may be extremely limited. Indeed, consciousness may have evolved merely to check – retrospectively – the operation of numerous unconscious processing systems that constantly manage the organism’s relationship with the environment.
This might be the reason why simple phobias are not amenable to reason. Most arachnophobics are perfectly aware that most spiders cannot harm them. Even so, they will still experience extremely high levels of fear when confronted by the most minute spider. Because consciousness is only loosely tethered to the underlying apparatus that generates fear, the intellect cannot be brought to bear on the problem. The unconscious simply won’t listen, preferring instead to abide by the time-honoured adage ‘better safe than sorry’. Individuals suffering from phobias may have inherited a first-class alarm system, but it is one that has now become something of a handicap in the controlled, protected environment afforded by civilisation.
In the modem world, power points and light sockets are ever present and potentially lethal; however, there are hardly any plug- or light-socket phobies. On the other hand, there are millions of individuals who fear harmless spiders, rarely encountered snakes, and domesticated dogs. The things that we fear most reflect our evolutionary history. We are still inclined to avoid those things that were best avoided on the plains of Africa. It would seem that we are born with nervous systems that have been ‘wired’ by natural selection to fear revenants from the ancestral environment – or at least wired to
learn tafear
revenants from the ancestral environment. For example, it might be that we are predisposed to acquire our own fears by observing the expression of fear in significant others (i.e. parents and peers). Thus, ancient fears could be preserved by a form of cultural transmission in which emotional distress is more readily associated with certain creatures.
This evolutionary bias in the incidence of phobias is called
preparedness,
and was first described by the psychologist Martin Seligman in the 1970s. Subsequent research has suggested three classes of stimuli that human beings are
prepared
to fear. Firstly, virtually anything that might be linked with disease. This is a very broad category, and may include substances that are perceived as dirty as well as certain creatures associated with decay and decomposition (e.g. maggots and worms). Secondly, animals that are either venomous or predatory. Thirdly, unfriendly
conspeciftcs
(i.e. other human beings whose facial expressions communicate hostile intentions). This latter category appears because human beings are social animals who live in dominance hierarchies. As such, it is as important to respond to threats arising from within the social group as it is to those arising from outside.
Even within these three categories, more precise predictions can be made concerning the potential of a particular stimulus to provoke fear. For example, with respect to animals, reptiles should evoke the greatest fear, because reptiles were the greatest threat to our very early mammalian ancestors. Reptiles are the archetypal foe. Perhaps this is why science-fiction B movies are so frequently populated by latex saurians. When we look at a snake and shiver, we do so because of an unconscious ‘memory’ that is some 224 million years old.
The preparedness hypothesis is well supported by studies employing Pavlovian conditioning. A neutral stimulus will eventually trigger fear if it has previously been paired with a negative stimulus (for example, an electric shock). It is easier to condition fearless subjects to show signs of fear when presented with pictures of snakes or hostile faces than it is with pictures of flowers or happy faces. Evolution has biased the associative machinery of the brain in order to increase the organism’s chances of survival.
The Swedish psychologist Arne Öhman has conducted a number of studies showing that prepared stimuli, even when presented outside of awareness, can initiate the fight/flight response. This is particularly evident in individuals for whom the presence of a phobia suggests an underlying neurophysiology sensitive to prepared stimuli. Elevated levels of arousal were detected by monitoring the skin conductance response (SCR), which reflects very subtle changes in sweat gland activity (see
Chapter 6
). Arachnophobie, ophidiophobics (those who fear snakes), and non-fearful subjects were shown pictures of spiders, snakes, flowers, and mushrooms. Although the pictures were shown for 30 milliseconds, they were rendered subliminal by the subsequent presentation of a masking stimulus – a second and more powerful stimulus that blocks awareness of the preceding exposure. None of the subjects could consciously identify any of the images appearing before the mask. Even so, ophidiophobic subjects showed elevated SCRs specific to snakes, arachnophobic subjects showed elevated SCRs specific to spiders, whereas non-phobic subjects showed the same level of response to all stimuli.
Subliminal presentations of prepared stimuli can also trigger the fear response in non-phobic subjects – albeit after conditioning. Öhman and his colleagues paired pictures of prepared and control stimuli with electric shocks before presenting them to subjects again in a masked form to ensure subliminality. Subjects conditioned to snakes or spiders, but not those conditioned to flowers or mushrooms, showed elevated SCRs. The same effect was achieved with angry and happy faces. After conditioning, elevated SCRs produced by angry faces survived masked presentation while those produced by happy faces did not.