Wednesday, 14 October 2015

Why Do We Sleep?

Sleep is a mysterious process - we spend a large proportion of our lives doing it, often having dreams which include vivid hallucinations. Why? What prompts our bodies and brain to go through this process on a daily basis?

Everyone sleeps. Image by PedroSimoes7

Role in other processes

Sleep can affect a number of areas of our waking lives, including:

 - Education: early risers get better school grades (Preckel et al., 2013)

 - Memory: sleep plays a major role in consolidating memories (Walker & Stickgold, 2004)

 - Creativity: people with later sleep cycles are more creative.

 - Mood: an afternoon nap can tune out negative emotions (Gujar et al., 2010)

 - Metal health: sleep problems are associated with stress and depression.

When people don't sleep, they lose the ability to concentrate on even the simplest of tasks, and begin to hallucinate and feel deeply paranoid (Lindzay et al., 1976). It is also so unpleasant that sleep deprivation is used as a form of torture.

What happens during sleep?

Activity in the brain changes over 5 sleep stages. The first four of these often just called stages 1-4, and during these, you fall into a progressively deeper sleep. In stage 5, 'REM sleep', the brain becomes more active again, and you begin to dream - something that Freud considered to be focused on 'wish fulfilment'.

Electrical activity in the brain changes over the sleep stages. One particular brain wave, the delta wave, has a very slow frequency and a high voltage, and is only normally found during deep sleep. There are no delta waves in stages 1 or 2. During the first stage, the brain’s activity is very similar to wakefulness with small rapid brain waves, but by stage 4, delta waves are dominating.

Because of this, stages 3-4 are often called delta sleep or slow-wave sleep (SWS), and it may be the case that these stages are especially important to allow the brain to consolidate episodic memories, and allow the brain to recover in order to store new memories the next day (Walker, 2009).

The evolution of sleep

The evolution of sleep is a puzzle, but we know that as it exists in animals as basic as the fruit fly, sleep must have served a useful function throughout our evolution.

All animals sleep; sloths sleep in the trees
for large parts of the day. Image by Brian Gratwicke.

On the surface, sleep might appear to be a waste of valuable hours in the day, as well as leaving animals vulnerable to attack. For this reason, sleep must be a valuable - perhaps essential - process, and must fulfil a function for which rest would not be enough.

One possibility is that sleep evolved because it helped our ancestors to repair damage to the body, giving them a survival advantage. However it would appear that resting would fulfil the same function, and sleep deprivation does not seem to cause much immediate physical harm to individuals.

Another suggestion is that sleep is essential for the nervous system. Resting does not cut the individual's nervous system off from external stimulation in the same way as sleep does, and this could be its key purpose (Cirelli and Tononi, 2008). It may well be that as organisms developed more complex brains, sleep evolved as a means of consolidating memories and restoring cognitive functions.

- More on theories of sleep and dreams to follow....


Cirelli C, Tononi G. Is sleep essential? PLoS Biol. 2008;6:1605–11.

Gujar, N., McDonald, S., Nishida, M., and Walker, M. (2010). A Role for REM Sleep in recalibrating the sensitivity of the human brain to specific emotions. Cerebral Cortex, 21(1), 115-123. doi: 10.1093/cercor/bhq064

Lindsey, G., Hall, C.S. and Thompson, R.F. (1978). Psychology (2nd Ed.) New York: Worth Publishers.

Preckel, F., Lipnevich, A., Boehme, K., Brandner, L., Georgi, K., K├Ânen, T., Mursin, K., and Roberts, R. (2013). Morningness-eveningness and educational outcomes: the lark has an advantage over the owl at high school. British Journal of Educational Psychology, 83(1), 114-134. doi: 10.1111/j.2044-8279.2011.02059.x

Walker, M.P. (2009). The role of slow wave sleep in memory processing. Journal of Clinical Sleep Medicine, 5(2 Suppl), S20.

Walker M.P. and Stickgold, R. (2004). Sleep-dependent learning and memory consolidation. Neuron, 30;44(1):121–33.

Monday, 28 September 2015

Introvert v's Extravert Personalities

An introvert is a person who prefers solitude or 1-to-1 interactions rather than busy social occasions, while an extravert is the opposite - they like to socialise, and don't particularly like to be alone.


However, this is a very simplistic distinction - most people really fall on a scale from one extreme to the other, with few of us entirely introverted or extraverted. Sometimes researchers use the term 'ambivert' to mean someone who is more or less equally balanced between the two.

The following image illustrates this idea of a scale between two extremes:

Introversion v's extraversion. Source: here.

Biological basis

According to researcher Hans Eysenck (1967), some people have a less sensitive nervous system than others do, and therefore need more environmental input for the same end result. They therefore need more social interaction in order to feel stimulated causing them to be extraverted, while those with more sensitive nervous systems feel overwhelmed with too much input, and therefore avoid it i.e. they are introverted. This biological theory is supported by evidence suggesting that personality appears early in life, and that personality traits remain steady over the lifespan (McCrae & Costa, 1997).

Social factors

The work of McCrae and Costa (1997) suggests that personality factors including extraversion are universal, and therefore relatively little influenced by culture. The society that we live in does make a difference to whether traits are encouraged or even accepted, however; in her 2013 book 'Quiet', Susan Cain argues that society increasingly values the extravert, with introverts being misunderstood and undervalued.

From a teaching point of view, it is undoubtedly true that the typical classroom today - with discussions, debates, and a social-constructivist approach to learning in general - is more geared to the extravert than to the introvert.


Eysenck, H. J. (1967). The Biological Basis of Personality. Springfield, IL: Thomas Publishing.
McCrae, R.R. and Costa, P.T. Jr (1997). Personality trait structure as a human universal. American Psychologist, 52(5), 509-516.

Monday, 1 June 2015

Help for Psychology Students

This site aims to provide useful information for Psychology students, especially in introductory courses such as GCSE, N5, Higher, A-Level and the early years of college or university study. It provides summaries of many classic Psychology research studies and theories. Some of the most popular posts can be seen in the sidebar, or use the search menu at the top of the screen to search by keyword. This is brought to you free of charge and without adverts. Comments are very welcome.

Some items that previously appeared on this blog - especially articles on educational theory - are now on my personal website,

Sunday, 31 May 2015

Kozorovitskiy et al (2006)


Marmosets are small monkeys, and are unusual among primates because males care extensively for their offspring. Kozorovitskiy et al. (2006) wanted to find out what effect this had on the monkey fathers' brains.


The researchers found that becoming a father resulted in important changes in the brains of male adult marmoset monkeys. Changes were found in the dendrites - the branching spines that connect neurones - in the frontal lobe of the monkey's brains. These were more complex than those of a control group of marmosets who were in mating pairs but were not fathers. 

Marmoset monkeys are good dads. Image by Tambako the jaguar


The changes could be explained in terms of the complex cognitive demands in caring behaviour, but the researchers noted a possible connection to the hormone vasopressin. The also note that the functional consequences of the change are not yet clear.

Human males, depending on culture, often play a major role in child rearing, and this finding has potential implications - with the usual caution about generalising cross-species.


Kozorovitskiy, Y., Hughes, M., Lee, K., and Gould, E. (2006). Fatherhood affects dendritic spiness and vassopressin V1a receptors in the primate prefrontal cortex. Nature Neuroscience, e9, 1094 - 1095. doi:10.1038/nn1753

Saturday, 30 May 2015

The Biological Approach

The biological approach to psychology is a contemporary approach which emphasises how processes within the body affect our thoughts and behaviour. It relates directly to the medical model of atypical behaviour, which explains mental illness in terms of bodily processes, and treats them using drugs.

Main principles

The approach tries to explain our behaviour in terms of 4 main biological systems:

  • The nervous system
  • Hormones
  • Genes

Of these, the most important is the nervous system - the nerves of the body, including the brain and spinal cord. It seems obvious to say that the brain controls behaviour - nobody in Psychology argues this point. However non-biological psychologists can take a 'black box' approach to the brain, saying that we don't need to study it directly in order to understand thoughts or behaviour.

Brain areas

Early ideas about the role of different brain areas were based on case studies of people who had suffered injuries or illnesses that damaged their brains, resulting in loss of specific psychological functions. One was the case of Phineas Gage - a man who survived a huge brain injury to his frontal lobe, but suffered a resulting personality change including a loss of self-control. Another was Paul Broca's patient 'Tan' who lost the ability to speak after losing a particular area of the left hemisphere which became known as Broca's area.

Nowadays, researchers have developed a much more sophisticated understanding of what areas of the brain do. One essential tool is the use of modern brain scans such as fMRI and PET scans, which allow the activity level of a person's brain to be seen on a screen at the same time as they are doing a task. Areas which 'light up' more are assumed to be important to the task. For example, if the frontal lobe lit up during a problem solving task, this would be evidence that this area of the brain is involved in problem solving.

An image from a PET scan of the brain. Photo by Reigh LeBlanc.

Brain cells

This approach views all psychological activity as fundamentally the product of brain cells communicating with each other. This happens through electrical impulses in a neurone travelling down the axon (nerve fibre) and then triggering the release of chemicals called neurotransmitters. Any time a person takes a drug such as caffeine, alcohol or cocaine, the drug is interfering with this process in some way - for example, by mimicking the neurotransmitter and making certain brain areas more active.

(Read more about how neurotransmitters work here).

Hormones and genes

Both hormones and genes have also been linked to behaviour. For example, in the area of atypical behaviour/psychopathology, disorders such as post-natal depression have been linked to a hormonal imbalance, while a range of disorders including schizophrenia have been shown to correlate to genetic factors - for example, if you have an identical twin with the disorder, then you are more likely to have it too. However, nobody has yet found 'the schizophrenic gene', as such.


With all of the biological factors that link to Psychology, there is a question of cause and effect. For example, if someone with a mood disorder has an atypical hormone or neurotransmitter level, is this the cause of their disorder, or is it a result of it?

Brain scans can be misleading - and may link to the over simplistic idea that a psychological function happens in one part of the brain. In fact, it may be better to think of processes as the result of communication between brain areas, rather than occurring a single place. The technology has also been shown to be at risk of false positives - such as showing activity in the brain of a dead salmon!

This approach has been accused of being reductionist - arguably, we can find more and more detail about the brain without really answering the big questions about Psychology.

Increasingly, this approach is making broad links across the subject. Cognitive neuroscience is the study of how cognition occurs in the brain, while social neuroscience means the study of how thought processes link to brain function.

See also this recent BPS digest article - Students seduced by superfluous neuroscience.

Friday, 22 May 2015

A Behavioural Sink: Calhoun's (1962) rat studies

Aggressive gangs of youths, neglectful parents, sexual assault - some of the worst aspects of modern human society. But could they simply be the products of the physical environment we live in?

That is exactly what researcher James Calhoun suggested with his groundbreaking studies on rodents - which found many of the same social problems cropping up in artificial and overcrowded 'rat cities' that he created in his lab.

What happens to a rat's behaviour when it is overcrowded? Image via Pixabay


The most obvious problem the rats suffered from was overcrowding. Things started off well with a total population of 48 rats across 4 enclosures, but they soon began to breed and multiply despite the limited space. The social structures that emerged were put under pressure, with it hard for any of the rats to defend their territory.

Psychological space

Interestingly, it was not just the size of the physical space that impacted on behaviour, but its layout. With the pen divided into four compartments, two were 'end' compartments with a single entranceway, and the remaining two were of equal size and shape, but had a pair of entrances, joining on to the other pens. The results in the two types of compartment were sharply contrasting. In the end compartments, a single male rat was able to dominate a territory, guarding the single entrance and keeping rivals out. Within these compartments, behaviour was essentially normal.

However in the middle compartments, this wasn't possible. It was here that the rats' behaviour degenerated so disturbingly:

- Male rats formed 'gangs' and attacked females and infants

- Females suffered massively increased birth complications

- Infants were forgotten or abandoned

- Some rats wounded, sexually attacked or even cannibalised other rats.

The rats changed so markedly that their behaviour was unrecognisable compared to rats in a more natural habitat - according to Calhoun, they had "stopped being rats".

What do people (and rats) need?

There will always be doubts about comparing animal experiments to humans, but this study had a huge impact because it seemed to tell us something profound about behaviour and psychological health.

The research strongly suggests that the answer to psychological health is not within our brains but within our environments - if our surroundings are positive, it seems to suggest, the chances of deviant and antisocial behaviours may be greatly reduced.

Read more

The social implications of Calhoun's work: 'Letting the Rat out of the Bag'
A similar study with implications for addiction: 'The View from Rat Park'.


Calhoun, J. B. (1962). Population density and social pathology. Scientific American, 206(3), 139–148.

Discussion points:

  • Was this study unethical?
  • Can the rat behaviour in the study be generalised to human behaviour?
  • What human environments might be similar to the 'middle compartments' in the study where most harmful behaviour was observed? 

Wednesday, 20 May 2015

Hazan & Shaver (1987) - the 'Love Quiz' study


Hazan and Shaver (1987) studied adult relationships to find out whether romantic love shows the same attachment styles as those found among children.

Like Bowlby, they believed that an infant’s attachment to the primary carer provides a schema of how relationships work that will be carried into adulthood. The implications of this, which they set out to test, is that similar attachment styles may be shown in adulthood as Ainsworth and Bell (1970) discovered among infants.

Can childhood attachments lead to adult
romantic behaviour? Image by Robert McGoldrick.


The researchers used a survey printed in a newspaper, presented as a “love quiz”. The first 620 responses were analysed – 205 from men and 415 from women. 42% of participants were married and 31% were dating. Questions asked about issues such as fear of closeness, jealousy and obsessive preoccupation.


The researchers analysed the responses to the questions and categorised each participant into one of three groups:
  • Securely attached: has a healthy balance between wanting closeness and being comfortable with independence.
  • Avoidant: tends to avoid closeness and is excessively independent, i.e. dislikes relying on others.
  • Anxious: clingy and insecure; is very uncomfortable with independence.
From the sample, 56% were secure, 25% avoidant and 19% anxious. These are very similar to the proportions of secure/insecure infants in the classic studies by Ainsworth and colleagues - supporting the researchers’ hypothesis.


A limitation is that there is no way of knowing if the same individuals who report secure adult relationships were also securely attached as children. Therefore, although the results did in principle support the researchers' continuity hypothesis of attachment styles through the lifespan, they didn't confirm it.

However, as the first attempt to link attachment style to adult relationships, this was a large-scale study and very successful.


Ainsworth, M.D.S. & Bell, S.M. (1970). Attachment, exploration, and separation: Individual differences in strange-situation behavior of one-year-olds. Child Development, 41, 49-67.
Hazan, C. and Shaver, P.R. (1987). Romantic love conceptualised as an attachment process. Journal of Personality and Social Psychology, 52(3), 511-524.