PSYCHOLOGY ‘A’

 

Biological School

 

Charles Darwin was born in 1809, the son of a distinguished physician. While studying at Cambridge University, he abandoned his plan to become ordained and acquired a keen interest in natural history. After graduation, the young Darwin was appointed as the resident naturalist aboard the survey ship HNS Beagle. A subsequent 5 year voyage to the South Pacific and South Atlantic prompted his first consideration of how species might evolve.

 

The concept of natural selection proved a convincing mechanism by which the development of a species could be explained. The propositions that provided the cornerstones of evolutionary theory are straightforward. Organisms produce more offspring than can survive and reproduce. The organisms that survive tend to be better adapted. Parental characteristics appear in this progeny (offspring of a person, animal or plant); thus, better adapted lines will survive and pass on their characteristics that give them an advantage.

 

Darwin suggested that complex organisms can evolve by slow cumulative change. Although Darwin did not know the exact mechanism that governed fundamental changes in the appearance of organisms, we now know that these are genetic. Each genetic change is the result of a mutation; however, the cumulative process of change, guided by natural selection, is therefore non-random. The fossil records, although marred by gaps and omissions, suggested that such a process of gradual change had occurred. Moreover, given enough time, the most complex of organisms, man, could evolve.

 

The concept of ‘design’ could now be abandoned. Without a design, there is no need to infer the presence of a designer (God). Humanity had simply evolved from an ape-like ancestor (Australopithecus). In 1859, Darwin published The Origin of the Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. The second major blow to the foundations of religion (or, creationism) had been struck.

 

The trajectory of descent has taken mental illness from the ethereal realms of the supernatural, to the pedestrian world of brain chemistry and disease. In effect, the extreme form of human suffering that we call mental illness lost its position as a subject fit for theologians and priests and fell into the scope of interest defined by science and medicine.

 

SOURCE: Tallis, F (1998) Changing Minds: The History of Psychotherapy as an Answer to Human Suffering London: Cassell

 

Up to the 19th century, the dominant view of how to explain the diversity in different types of animal in existence in the world was in terms of God’s creation. A divine purpose was revealed in His work. Humans were created as beings fundamentally different from animals – we were endowed with an immortal soul, free will and moral insight (Roth, 1997).

 

Today the dominant explanatory mechanism to account for the diversity of the animal form is Darwin’s theory of evolution by natural selection. Some thinkers believe that Darwin made God redundant. Others, such as Hoyle (1983) believe that evolution in Darwin’s terms is only part of the story and that there is a purposive intelligence at work in the universe.

 

Nonetheless, it is estimated that life, in its simplest form, first appeared on earth around 4,000 million years ago. There are now over 1 million different species of organism in existence. Darwin’s theory begins with the idea that the physical characteristics of an organism are important for its survival and for its success in reproducing itself.

 

Within a given species, individual animals vary in the individual characteristics that are relevant to its survival and reproduction. For example, some rats have stronger legs than others, and some kestrels have better eyes than others and so on. The stronger the rat’s legs, the faster it can run, the longer it is likely to live, and, in general, the more offspring it will leave to posterity. The environment is such as to allow only some of the offspring of an organism to flourish. Some will die, for example, of starvation or be caught by a predator before reaching sexual maturity. Suppose that a particular feature that gives an animal an advantage is passed on to its offspring through genetic inheritance. For example, consider a rat that possesses genes that contain information for producing particularly strong legs. Such a rat will endow at least some of its offspring with similar genes, coding for stronger legs. Because of their greater speed, rats of this kind will prosper at the expense of slower rats. They will expand in numbers. In other words, the population of rats will change or evolve (Roth, 1997).

 

By this stage, you might wonder why the legs simply do not go on for ever getting stronger and stronger, and thus why a ‘lightening-fast’ ‘super-rat’ does not evolve. The answer is that, apart from advantages, ‘super legs’ would bring disadvantages. For example, the rat would get heavier, which would necessitate higher energy input and more food being found. Being bigger, the number of escape routes available to the rat in an emergency would diminish. Evolution would be expected to find a compromise, in effect trading off advantages with disadvantages. The term ‘natural selection’ refers to traits, such as strong legs, being perpetuated according to their survival value in a particular environment. In the language of evolutionary theory, we might say that a successful organism is one that is well adapted to its environment and so survives to donate to its offspring. For example, the zebra’s stripes offer good camouflage…the owl’s excellent nocturnal vision serves its ability to find prey (Roth, 1997).

 

Clearly, in order to reproduce, an organism must survive to the age at which it is sexually mature. After that, the longer it stays alive at an age at which it able to reproduce, the greater are its chances of endowing posterity with offspring. In biological terms, the term fitness (not to be confused with athletic prowess!!!) refers to the ability of an organism to survive and produce offspring that can themselves survive and produce offspring (Roth, 1997).

 

Darwin provided three pieces of evidence to support his assertion that species evolve: 1) He documented the fossil records through progressively more recent geographical layers. 2) He described striking structural similarities among living species (e.g. the human arm and the wing of a bird), which suggested that they had evolved from common ancestors. 3) He pointed to the major changes that had been brought about in domestic plants and animals by programmes of selective breeding. However, the most convincing evidence of evolution comes from direct observation of evolution in progress. For example, Grant (1991) observed evolution of the finches of the Galapagos Islands – a population studied by Darwin himself – after only a single season of drought. An 18 month drought on the Islands left only large, difficult to eat, seeds. Nonetheless, the beak size of the finches increased in size to accommodate the large, difficult to eat seeds (Pinel, 2003).

 

Darwin argued that evolution occurs through natural selection. He pointed out that members of each species vary greatly in their structure, physiology, and behaviour, and that the heritable traits that are associated with high rates of survival and reproduction are the ones most likely to be passed on to future generations. He argued that natural selection, when repeated generation after generation, leads to the evolution of species that are better adapted to surviving and reproducing in their particular environmental niche. Darwin called this process natural selection to emphasise its similarity to the artificial selective breeding practices employed by breeders of domestic animals. Just as horse breeders create faster horses by selectively breeding the fastest of their existing stock, nature creates fitter animals by selectively breeding the fittest. Fitness, in the Darwinian sense, is the ability of an organism to survive and contribute its genes to the next generation.

Mind Body Connection

Most experts in the field of psychology and biology agree that the mind and the body are connected in more complex ways than we can even comprehend. Research constantly shows us that the way we think affects the way we behave, the way we feel, and the way our bodies respond. Also, physical illness, physical exhilaration, exercising, and insomnia all affect the way we feel and behave, but also the way we think about ourselves and the world.

The idea that human processes fall into two categories (physiological and psychological) grew out of the17th century conflict between science and the Roman Church. For much of the history of Western civilisation, truth was whatever was decreed to be true by the Church. Then, in about 1400AD, things started to change. The famines, the plagues, the marauding armies that had recently swept through Europe during the Middle Ages (European historical period between roughly AD 500 and 1450.) subsided, and interest turned to commerce, scholarship and art – this period (1400 – 1700AD) is known as the Renaissance (rebirth). Some renaissance scholars were not content to follow the dictates of the Church; instead, they started to study things directly, by observing them – and so it was that modern science was born (Pinel, 2003).

Much of the scientific knowledge that was accumulated during the renaissance was at odds with the Church. However, the conflict was resolved by the prominent French philosopher Rene Descartes (pronounced day cart). Descartes (1596-1650) proposed a philosophy that, in a sense, gave one part of the universe to science and the other part to the Church. He proposed that the universe is composed of two elements: 1) Physical Matter, which behaves according to the laws of nature and is thus a suitable object of scientific investigation; and 2) the Human Mind (Soul or Spirit), which lacks physical substance, controls human behaviour, obeys no natural laws, and is thus the appropriate purview of the Church. The human body, including the brain, was assumed to be entirely physical. The body and brain of non-human animals were also considered to be entirely physical (Pinel, 2003).

Cartesian Dualism, as Descartes philosophy became known, was sanctioned by the Roman Church, and so the idea that the human brain and the mind are separate entities became widely accepted. It has survived to this day, despite the intervening centuries of scientific progress. Most people now understand that human behaviour has a physiological basis, but many still cling to the dualistic assumption that there is a category of human activity that somehow transcends the human brain (Searle, 2000).

Evolution of the human brain:

Early research on the evolution of the human brain focused on size. This research was stimulated by the assumption that brain size and intellectual capacity were closely related – an assumption that quickly ran into two problems: First, it was shown that modern humans, whom modern humans, believe to be the most intelligent of all creatures, do not have the biggest brains. With brains weighing about 1,350 grams, humans rank way behind whales and elephants, whose brains weigh between 5,000 and 8,000 grams (Harvey and Krebs, 1990). Second, the sizes of the brains of acclaimed intellectuals (e.g. Einstein) were found to be unremarkable. It is now clear that, although healthy adult brains vary greatly in size – between 1,000 and 2,000 grams – there is no clear relationship between brain size and intelligence (Pinel, 2003).

One obvious problem in relating brain size to intelligence is the fact that larger animals tend to have larger brains, presumably because larger bodies require more brain tissue to control and regulate them. Thus, the facts that large men tend to have larger brains than small men, that men tend to have bigger brains than women, and that elephants have larger brains than humans do not suggest anything about the relative intelligence of these populations. This problem led to the proposal that brain weight expressed as a percentage of total body weight might be a better measure of intellectual capacity. This measure allows humans (2.33%) to take their rightful place ahead of elephants (0.20%); however, it also allows both humans and elephants to be surpassed by that intellectual giant of the animal kingdom – the shrew (3.33%).

A more reasonable approach to the study of brain evolution has been to compare the evolution of different brain regions (Finlay and Darlington, 1995; Killacky, 1995). For example, it has been informative to consider the evolution of the brain stem separately from the evolution of the cerebrum (cerebral hemispheres). In general, the brain stem regulates reflex activities that are critical for survival (e.g. heart rate, respiration, and blood glucose levels), whereas the cerebrum is involved in more complex adaptive processes such as learning, perception and motivation (Pinel, 2003). The biggest increase in humans has been the cerebrum, which evolved convolutions (folds on the cerebral surface) to accommodate the increasing capacity of the human brain.

Divisions of the Nervous System:

 

The vertebrate nervous system is composed of two divisions: The central nervous system (CNS) is the division of the nervous system that is located within the skull and the spine. The peripheral nervous system (PNS) is the division that is located outside the skull and spine.

 

The central nervous system is composed of two divisions: The brain is the part of the CNS that is located in the skull; the spinal cord is the part that is located in the spine.

 

The peripheral nervous system is also composed of two divisions:

 

The somatic nervous system (SNS) is the part of the PNS that interacts with the external environment. It is composed of afferent nerves that carry sensory signals from the skin, skeletal muscles, joints, eyes, ears, and so on, to the central nervous system, and efferent nerves that carry motor signals from the central nervous system to the skeletal muscles.

 

The autonomic nervous system (ANS) is the part of the PNS that participates in the regulation of the internal environment. It is composed of afferent nerves that carry sensory signals from internal organs to the CNS and efferent nerves that carry motor signals from the CNS to the internal organs. You will not confuse the terms afferent and efferent if you consider the brain and remember that many words that involve the idea of going towards something – in this case the brain – begin with an ‘a’ (e.g. advance, approach, arrive) and that many words that involve going away from something begin with an ‘e’ (e.g. exit, embark, escape) (Pinel, 2003). The autonomic nervous system has two kinds of efferent nerves: sympathetic nerves and parasympathetic nerves. The sympathetic nerves are those autonomic nerves that project out from the CNS in the lumbar (small of the back) and thoracic (chest area) regions of the spine. The parasympathetic nerves are those autonomic motor nerves that project from the brain and sacral (lower back).

 

 

Nervous System

 

                                                                                   

Peripheral Nervous System                                Central Nervous System

 

 


                                                                                                                       

 

Brain               Spinal Cord

 

 

 

 

 

 

 


Somatic Nervous System               Autonomic Nervous System         

                                                                                               

                                                                                               

 

 

  Afferent                Efferent                    Afferent                   Efferent

  Nerves                 Nerves                     Nerves                    Nerves

 

 

 


  

Parasympathetic    Sympathetic

                                                                        Nervous                      Nervous

                                                                        System                       System

 

 

A quick guide to the brain:

 

The average human brain contains around 100 billion neurons. These neurons are the building blocks of the nervous system. These neurons ‘talk to each other’. Of course, they do not talk to each other like you and I do. However, they do pass signals to one another using their own special language. This language is known as a neurotransmitter, and just as there are several languages that humans use, there are several neurotransmitters in the brain. So, just as we speak English, French, Japanese or German, neurons can speak using different neurotransmitters. Some examples of neurotransmitters are dopamine, serotonin and gamma-aminobutyric acid (GABA). These neurotransmitters are just chemical substances that allow a message to pass from one neuron to another. The actual message is in the form of a nerve impulse (a change in the electrical potential of a neuron).

 

Why do neurons need to use neurotransmitters? There are tiny gaps between neurons called synaptic gaps (or synapses for short). A nerve impulse can’t pass through this gap so if a neuron wants to communicate with another neuron it has to fill this gap with a neurotransmitter. The neuron squirts some neurotransmitter into the gap allowing the message (the nerve impulse) to pass to the next neuron. Once the message has been sent, the synapse has been emptied. There are two crucial processes involved in this: reuptake and degradation.

 

Reuptake: is where the neurotransmitter in the synapse is reabsorbed into the neuron that sent the message.

 

Degradation: is where the neuron receiving the message releases an enzyme that breaks down the neurotransmitter in the synapse.

Neurotransmitters

A Neuron is a specialized nerve cell that receives, processes, and transmits information to other cells in the body. We have a fixed number of neurons, which means they do not regenerate. About 10,000 neurons die everyday, but since we start out with between ten and 100 billion (Hooper & Teresi, 1987), we only lose about 2% over our lifetime.

Information comes into the neuron through the Dendrites from other neurons. It then continues to the Cell Body – (soma) which is the main part of the neuron, which contains the nucleus and maintains the life sustaining functions of the neuron. The soma processes information and then passes it along the Axon. At the end of the axon are bulb-like structures called Terminal Buttons that pass the information on to glands, muscles, or other neurons.

 

 

 

Anatomy of a Neuron

 

 

Information is carried by biochemical substances called neurotransmitters, which we will talk about in more detail shortly. The terminal buttons and the dendrites of other neurons do not touch, but instead pass the information containing neurotransmitters through a Synapse. Once the neurotransmitter leaves the axon, and passes through the synapse, it is caught on the dendrite by what are termed Receptor Sites.

Neurotransmitters have been studied quite a bit in relation to psychology and human behaviour. What we have found is that several neurotransmitters play a role in the way we behave, learn, the way we feel, and sleep. And, some play a role in mental illnesses. The following are those neurotransmitters which play a significant role in our mental health.

Acetylcholine – involved in voluntary movement, learning, memory, and sleep

§ Too much acetylcholine is associated with depression, and too little in the hippocampus has been associated with dementia.

Dopamine – correlated with movement, attention, and learning

§ Too much dopamine has been associated with schizophrenia, and too little is associated with some forms of depression as well as the muscular rigidity and tremors found in Parkinson’s disease.

Norepinephrine – associated with eating, alertness

§ Too little norepinephrine has been associated with depression, while an excess has been associated with schizophrenia.

Epinephrine – involved in energy, and glucose metabolism

§ Too little epinephrine has been associated with depression.

Serotonin – plays a role in mood, sleep, appetite, and impulsive and aggressive behaviour

§ Too little serotonin is associated with depression and some anxiety disorders, especially obsessive-compulsive disorder. Some antidepressant medications increase the availability of serotonin at the receptor sites.

GABA (Gamma-Amino Butyric Acid) – inhibits excitation and anxiety

§ Too little GABA is associated with anxiety and anxiety disorders. Some antianxiety medication increases GABA at the receptor sites.

Endorphins – involved in pain relief and feelings of pleasure and contentedness

Please note that these associations are merely correlations, and do not necessarily demonstrate any cause and effect relationship. We don’t know what other variables may be affecting both the neurotransmitter and the mental illness, and we don’t know if the change in the neurotransmitter causes the illness, or the illness causes the change in the neurotransmitter.

                                               

Brain Systems:

 

If neurons are the building blocks of the brain, then it must surely have some ‘buildings’. In fact, there are many structures that have been identified in the brain. It is easiest to think of the brain in terms of three layers:

 

A central core

The limbic system

The cerebrum

 

The central core is really where the spinal cord meets the brain. This whole system can, broadly speaking, be thought of as dealing with basic primitive functioning. For example, it contains the cerebellum, which deals primarily with movement, but has also been implicated in reflexive learning such as conditioning (Legg, 1989). Two other key structures in this core are the thalamus and hypothalamus. The thalamus is like a relay station and especially relays messages from sense receptors (e.g. vision, hearing, taste and touch) to the cerebrum, where they are processed. The hypothalamus is a smaller structure but no less important. In fact, this structure is thought to control basic functions such as eating, drinking and sexual activity. Stimulating different parts of the hypothalamus also causes sensations of pain and pleasure.

 

The limbic system sits snugly around the central core, and in particular is closely connected to the hypothalamus. This area is relatively large in mammals compared to animals such as fish and reptiles and so it’s thought to regulate the primitive functions of the hypothalamus. So, for example, while you’ll rarely see fish or reptiles being disrupted from important duties such as eating, killing, running away or procreating, mammals appear to inhibit these urges when required. One important structure in the limbic system is the hippocampus, which is very important in forming memories. The limbic system also seems to have a crucial role in emotion: for example, damage to this area can lead to increased aggression. Importantly, neurons in the limbic system use noradrenergic neurotransmitters for communication: these neurotransmitters are norepinephrine, serotonin, and dopamine. These neurotransmitters are implicated in many forms of psychological disorders such as schizophrenia and depression.

 

The cerebrum (which includes the cerebral cortex). This part of the brain is highly developed in humans and, without going into too much detail about its structure, this seems to be the ‘interpretation centre’ of the brain. It is in these areas that we have visual areas (for interpreting what we see) and auditory areas (for interpreting what we hear) and motor areas (for interpreting what we physically feel), and so on. You shouldn’t think that these areas are independent. In fact, although some structures are quite discreet, many of them blur into areas around them and it’s often very hard to tell where one structure ends and the next begins. Also, different areas are connected to each other in all manner of complex ways.

A final thing about the brain is that it is full of holes. These holes are called ventricles, and they are filled with fluid.

The biological model suggests that psychological problems are caused by problems in the brain. For example: Structural abnormalities; if the ventricles in the brain are particularly large this implies that these ‘holes’ are taking up space that would otherwise be occupied by brain tissue. Hormones; disorders could be due to abnormal levels of certain hormones (for example, he secretion of cortisol during stress). The hypothalamus has a central role in controlling hormone secretion, so if the structure goes wrong then you could end up with too many or too few hormones rushing around your body. Neurology; if the processes of degradation and reuptake go wrong you end up with too much or too little neurotransmitter in your synapses. These chemicals might be the cause of psychological problems. Genetics; any of those above problems could result from genetic factors (inherited structural abnormalities, hormone imbalances or neurological factors).

The Brain and Nervous System structure / lobes

The nervous system is broken down into two major systems: Central Nervous System and Peripheral Nervous System.

The Central Nervous System consists of the brain and the spinal cord. The Cerebral Cortex, which is involved in a variety of higher cognitive, emotional, sensory, and motor functions, is more developed in humans than any other animal. It is what we see when we picture a human brain, the gray matter with a multitude of folds covering the cerebrum. The brain is divided into two symmetrical hemispheres: left (language, the ‘rational’ half of the brain, associated with analytical thinking and logical abilities) and right (more involved with musical and artistic abilities). The brain is also divided into four lobes:

o Frontal – (motor cortex) motor behaviour, expressive language, higher level cognitive processes, and orientation to person, place, time, and situation

o Parietal – (somatosensory Cortex) involved in the processing of touch, pressure, temperature, and pain

o Occipital – (visual cortex) interpretation of visual information

o Temporal – (auditory cortex) receptive language (understanding language), as well as memory and emotion

Typically the brain and spinal cord act together, but there are some actions, such as those associated with pain, where the spinal cord acts even before the information enters the brain for processing. The spinal cord consists of the Brainstem which is involved in life sustaining functions. Damage to the brainstem is very often fatal.

Other parts of the brainstem include the:

Medulla Oblongata, which controls heartbeat, breathing, blood pressure, digestion;

Reticular Activating System (Reticular Formation), involved in arousal and attention, sleep and wakefulness, and control of reflexes;

Pons – regulates states of arousal, including sleep and dreaming.

Cerebellum – balance, smooth movement, and posture

Thalamus – "central switching station" – relays incoming sensory information (except olfactory) to the brain

Hypothalamus – controls the autonomic nervous system, and therefore maintains the body’s homeostasis, which we will discuss later (controls body temperature, metabolism, and appetite. Translates extreme emotions into physical responses.

Limbic System – emotional expression, particularly the emotional component of behaviour, memory, and motivation

Amygdala – attaches emotional significance to information and mediates both defensive and aggressive behaviour

Hippocampus – involved more in memory, and the transfer of information from short-term to long-term memory

The Peripheral Nervous System is divided into two sub-systems.  The Somatic Nervous System – primary function is to regulate the actions of the skeletal muscles. Often thought of as mediating voluntary activity.  The other sub-system, called the Autonomic Nervous System, regulates primarily involuntary activity such as heart rate, breathing, blood pressure, and digestion.  Although these activities are considered involuntary, they can be altered either through specific events or through changing our perceptions about a specific experience.  This system is further broken down into two complimentary systems:  Sympathetic and Parasympathetic Nervous Systems.

The Sympathetic Nervous System controls what has been called the "Fight or Flight" phenomenon because of its control over the necessary bodily changes needed when we are faced with a situation where we may need to defend ourselves or escape.  Imagine walking down a dark street at night by yourself.  Suddenly you hear what you suspect are footsteps approaching you rapidly.  What happens?  

Your Sympathetic Nervous System kicks in to prepare your body: your heart rate quickens to get more blood to the muscles, your breathing becomes faster and deeper to increase your oxygen, blood flow is diverted from the organs so digestion is reduced and the skin gets cold and clammy and rerouted so to speak to the muscles, and your pupils dilate for better vision.  In an instant, your body is prepared to either defend or escape.

Now imagine that the footsteps belong to a good friend who catches up to you and offers to walk you home.  You feel relief instantly, but your body takes longer to adjust.  In order to return everything to normal, the Parasympathetic Nervous System kicks in.  This system is slow acting, unlike its counterpart, and may take several minutes or even longer to get your body back to where it was before the scare.

These two subsystems are at work constantly shifting your body to more prepared states and more relaxed states.  Every time a potentially threatening experience occurs (e.g., someone slams on their breaks in front of you, you hear a noise in your house at night, you hear a loud bang, a stranger taps you on the shoulder unexpectedly), your body reacts.  The constant shifting of control between these two systems keeps your body ready for your current situation.

 

Evolution: a brief definition.

Futuyma, (1986) one of the most respected evolutionary biologists, has defined biological evolution as follows:

"In the broadest sense, evolution is merely change, and so is all-pervasive; galaxies, languages, and political systems all evolve. Biological evolution ... is change in the properties of populations of organisms...the changes in populations that are considered evolutionary are those that are inheritable via the genetic material from one generation to the next. Biological evolution may be slight or substantial; it embraces everything from slight changes in the proportion of different alleles within a population (such as those determining blood types) to the successive alterations that led from the earliest protoorganism to snails, bees, giraffes, and dandelions."

 

Allele: one of two or more alternative forms of a gene; for example, one allele of the gene for eye colour codes for blue eyes, while another allele codes for brown eyes

 

“Evolution is a process that results in heritable changes in a population spread over many generations” (Curtis and Barnes, 1989).

This is a good working scientific definition of evolution; one that can be used to distinguish between evolution and similar changes that are not evolution. Another common short definition of evolution can be found in many textbooks:

"In fact, evolution can be precisely defined as any change in the frequency of alleles within a gene pool from one generation to the next." (Curtis and Barnes, 1989).

 

When biologists say that they have observed evolution, they mean that they have detected a change in the frequency of genes in a population. When biologists say that humans and chimps have evolved from a common ancestor they mean that there have been successive heritable changes in the two separated populations since they became isolated.

Unfortunately the common definitions of evolution outside of the scientific community are different. For example, in the Oxford Concise Science Dictionary we find the following definition:

"evolution: The gradual process by which the present diversity of plant and animal life arose from the earliest and most primitive organisms, which is believed to have been continuing for the past 3000 million years."

 

This is inexcusable for a dictionary of science. Not only does this definition exclude prokaryotes (organisms whose genetic material is not enclosed by a nucleus. The most common examples are bacteria), protozoa (the lowest great division of the animal kingdom. These animals are composed of a gelatinous material, and show scarcely any trace of distinct organs), and fungi, but it specifically includes a term "gradual process" which should not be part of the definition. More importantly the definition seems to refer more to the history of evolution than to evolution itself. Using this definition it is possible to debate whether evolution is still occurring, but the definition provides no easy way of distinguishing evolution from other processes. For example, is the increase in height among Caucasians over the past several hundred years an example of evolution? Are the colour changes in the peppered moth population examples of evolution? This is not a scientific definition (Moran, 1993).

Standard dictionaries are even worse.

"evolution: ...the doctrine according to which higher forms of life have gradually arisen out of lower..." - Chambers (Moran, 1993)

"evolution: ...the development of a species, organism, or organ from its original or primitive state to its present or specialized state; phylogeny or ontogeny" - Webster's (Moran, 1993)

These definitions are simply wrong. Unfortunately it is common for non-scientists to enter into a discussion about evolution with such a definition in mind. This often leads to fruitless debate since the experts are thinking about evolution from a different perspective. When someone claims that they don't believe in evolution they cannot be referring to an acceptable scientific definition of evolution because that would be denying something which is easy to demonstrate. It would be like saying that they don't believe in gravity! (Moran, 1993)

Biological therapy

Some techniques that have traditionally been used are psychosurgery (surgery on the part of the brain thought to be at the root of the problem) or electroconvulsive therapy (ECT) (ECT is where a seizure is induced by passing 70-130 volts of electricity through a patient’s brain (this used to be done to both sides of the brain but nowadays is typically administered only to the nondominant right hemisphere). ECT is typically used only on severely depressed individuals, and psychosurgery would also be used as a last resort to a problem. By far the most common solution is to administer drugs aimed at increasing or reducing levels of neurotransmitters in the brain. This can be done in numerous ways: increase the production of neurotransmitter, prevent reuptake or degradation of a neurotransmitter. Drugs can also be used to redress hormone imbalances. The important thing when evaluating drugs is to compare the effect of a drug while controlling for psychological factors; this is done using what’s called a placebo treatment.

A placebo treatment is a treatment designed to make the patient believe they are being treated when, in fact, the intervention has no therapeutic value. An example of a placebo would be if you gave someone a white pill made of sugar to cure their headache and told then it was aspirin; sugar has no beneficial effect on headaches, but the patient would believe they were being treated because they think the pill is aspirin.

In any clinical trial testing the effect of a drug it is important to have a group of people who they are taking the drug, but are in fact taking something that has no effect. All patients must believe they are taking the drug and, better still, the researcher should not know who has been given the drug and who has been given the placebo (this is known as a double blind trial). If the placebo drug has an effect then we know that it is because of psychological factors: the effect represents how much improvement (or deterioration) you would get simply from the effect of someone believing they are taking a helpful medication. You might think that just believing you’re taking a drug that will help you will not have a strong effect, but, in fact, placebo effects can be very powerful.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

REFERENCES:

 

Curtis, H and Barnes, NS (1989) Biology 5th edition Worth Publishers

 

Futuyma, DJ (1986) Evolutionary Biology, Sinauer Associates

 

Grant, PR (1991) Natural Selection of Darwin’s Finches Scientific America 265, 82-72 (in) Pinel, JP (2003) Evolution, Genetics and Experience Biopsychology 5th edition, chapter 2, Pearson Education Inc.

 

Moran, L (1993) (online) The Talk.Origins Archive: Explaining the Creation/Evolution Controversy: What is Evolution Accessed: 10-07-2005 http://www.talkorigins.org/faqs/evolution-definition.html

 

Pinel, JP (2003) Evolution, Genetics and Experience Biopsychology 5th edition, chapter 2, Pearson Education Inc.

 

Roth, I (1997) The Open University’s Introduction to Psychology: volume 1 Psychology Press

 

Searle, SJ (2000) Consciousness Annual Review of Neuroscience 23, 557-578 (in) Pinel, JP (2003) Evolution, Genetics and Experience Biopsychology 5th edition, chapter 2, Pearson Education Inc.

 

Tallis, F (1998) Changing Minds: The History of Psychotherapy as an Answer to Human Suffering London: Cassell