Saturday, 28 March 2015

Stress, and its Origins in our Evolutionary Past

Stress is a major threat to physical and psychological health.  One reason that we experience so much stress is that many of the demands of modern life differ from what we are evolutionarily adapted to.  We have a stress response that helps us fight an attacker or run away (the 'fight or flight' response), but modern stressors are more likely to involve late trains or work deadlines.

For most of evolution, a human's lifestyle was very different
to what we experience today. Image: Wyoming_Jackrabbit

Often we can't avoid stressors, and we can't easily change the basic biological response of the human body.  Attention has therefore focused on ways of coping with life stress.  Methods include:

  • Exercise.  This is effective, because it naturally metabolises the stress hormones and excess glucose released during fight-or-flight.  However, it is not always possible to fit in a run during busy times!
  • Time management.  Often the best way to deal with the stressor is to avoid it - by prioritising, and managing deadlines more carefully.
  • Meditation.  This can be effective, and is easier to fit in than some alternatives.  The individual focuses on a simple stimulus such as a chant or a candle.  It can provide a simple way of clearing the mind from worries, and incorporates deep breathing which helps deactivate the stress response.  When meditating, people are both relaxed and alert.

Slagter et al. (2007) studied whether meditation can help people over the long-term as well.  They found that three months of meditation improved participants’ abilities to perform an attention-based task, which involved spotting numbers among a group of letters. This shows that meditation can help people to deal with life demands.


Slagter, H.A., Lutz, A., Greischar, L.L., Francis, A.D., Nieuwenhuis, S., Davis, J.M. and Davidson, R.J. (2007). Mental training affects distribution of limited brain resources. PloS Biology, 5, e138.

Friday, 20 February 2015

Brilliant Video - Evolution Condensed into 60 Seconds

Wow - a great video for putting human evolution in perspective:

"Evolution in 60 seconds", counting down from the beginning of life to the present day. Excellent for getting a sense of the overall timescale, and of when things like mammals and birds appeared on the scene.

My only criticism is that the focus on primates/humans could perpetuate the myth that evolution was somehow working towards humans as an end point, which is of course false. They could just as easily have counted down to the evolution of aardvarks!

Having said that, from a teaching point of view it would be great to see a similar video just on human origins for the past 8 million years or so, like the Smithsonian Institution's interactive timeline.

Saturday, 14 February 2015

Sternberg Quote

"When we teach only for facts, rather than for how to go beyond facts, we teach students how to get out of date." Robert Sternberg (2008:21)

Sternberg, R.J. (2008). Assessing what matters. Educational Leadership, 65(4), 20-26.

Wednesday, 11 February 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

One thing that is clear is that 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 alpha 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 recent evolution.

Sleep presents certain risks to animals. Image by Juan Carlos Vindas.

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 simply resting would not be enough.

One possibility is that sleep developed through evolution 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 & Tononi, 2008). It may well be then, 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., Könen, 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.

Thursday, 8 January 2015

Quote from Ken Robinson

Sir Ken Robinson is a British educationalist who promotes the importance of individualism and fostering creativity in our education systems. This quote comes from his book 'Out of Our Minds: Learning to be Creative':

"Academic ability is not the same as intelligence... If there were no more to human intelligence than academic ability, most of human culture would not have happened. There would be no practical science or technology, no business, no arts, no music, no dance, drama, architecture, design, cuisine, aesthetics, feelings, relationships, emotions or love. I think these are large factors to leave out of the account of intelligence. If all you had was academic ability, you wouldn't have been able to get out of bed this morning. In fact, there wouldn't have been a bed to get out of." (Robinson, 2001: 81).

 - View Ken Robinson's TED talk, 'How Schools Kill Creativity', here.


Robinson, K. (2001).  Out of our Minds: Learning to be creative.  Chichester: Capstone Publishing. (p. 81).

Tuesday, 25 November 2014

The Social Brain Hypothesis

What caused human brains - and those of other apes - to grow so large? One theory is that it resulted from the complexity of our environment - the day to day problems that our ancestors would have encountered in foraging and survival: Where are the fruit trees? Which ones did I pick from yesterday?

Another idea - the social brain hypothesis - is that the complexity of our social groups require a big brain to keep track of, especially when the group is large - a bigger group means more relationships to remember.

Doing either of these things well could potentially lead to a survival advantage, but which actually triggered the evolution of our unique brain size? Dunbar (1992) put the two theories to the test by comparing both foraging area and group size with neocortex ratio - the proportion of brain neocortex to other brain areas (considered a better measure of overall 'braininess' than absolute brain size or brain:body ratio).

A clear correlation was found - a bigger group meant a larger neocortex ratio, supporting the social brain hypothesis. In contrast there was no clear relationship between brain size and environmental complexity. It would appear that primates with larger social groups need larger brains in order to keep track of relationships. That is not to say, as Dunbar comments, that those large brains couldn't then be useful for dealing with environmental problems - but he does not feel it was the evolutionary driving force (Dunbar, 1998).

Chimps, like humans, are highly social animals. Image
by Benjamin Jakabek

Human Groups

Since the early work with other primates, Dunbar began to question whether the same principle would apply to human social groups. To fit with the ratio that had been found, a group size of around 150 would be predicted (Dunbar, 1998). In the modern world, however, it is difficult to define what constitutes our social group. Work colleagues? Friends and family? Neighbours? However, looking at hunter-gatherer tribes and at historical settlements, groups of around 120-150 members abound (Dunbar, 1993).

In a neat application to the modern world, Hill and Dunbar (2003) looked at the size of networks to which people send Christmas cards. It fitted the theory - 153.5 was the mean total population of the households receiving cards from any individual. This was only a fraction over the predicted maximum number - and in practice, senders of cards would probably not know every member of a recipient household equally well.

More recently, other researchers have started to look at new technology and social media, to ask whether technological developments have expanded the size of our natural social network. It appears that they haven't - despite the large number of contacts people often establish on Twitter, the number they regularly communicate with remains under 200 (Gonçalves et al., 2011).


The key idea from the social brain hypothesis is that evolution has determined a cognitive limit on what we can do; just as we have other mental limits such as short-term memory capacity, the brain is simply not capable of maintaining a greater number of close social relationships.

What does this number mean in practice? An obvious question to ask is how close a relationship has to be to count within the number. Do colleagues and extended family count? Just how do we define who is in our 150 and who is not? According to Dunbar, a simple way to look at it is as "the number of people you would not feel embarrassed about joining uninvited for a drink if you happened to bump into them in a bar" (Bennett, 2013).


Dunbar's number does seem to be applicable to a large number of situations, from historic communities to hunter gatherer tribes, from the size of army units to Twitter engagement.

However not everyone is convinced. A correlation between brain size and social group size does not prove that there was an evolutionary cause-and-effect. And de Ruiter et al. (2011) have argued that although the neocortex plays an important role in social functioning, its size does not directly determine social skills.

It could also be argued that Dunbar has cherry-picked examples that fit the theory post-hoc, and that had the number from the correlation calculation been different (say 250), he would have been able to find examples of human communities to fit.


Bennett, D. (2012). The Dunbar Number, From the Guru of Social Networks. Retrieved 20/11/2014 from:

Dunbar, R.I.M. (1992). Neocortex size as a constraint on group size in primates. Journal of Human Evolution, 22, 469-493.

Dunbar, R.I.M. (1993). Coevolution of neocortical size, group size and language in humans. Behavioural and Brain Sciences, 16, 681-735.

Dunbar, R.I.M. (1998). The social brain hypothesis. Brain, 9(10), 178-190.

Gonçalves, B., Perra, N. and Vespignani, A. (2011). Modeling Users' Activity on Twitter Networks: Validation of Dunbar's Number. PLoS ONE, 6(8): e22656. doi:10.1371/journal.pone.0022656

Hill, R.A. and Dunbar, R.I.M (2003). Social network size in humansHuman Nature, 14(1), 53-72.

de Ruiter, J., Weston, G. and Lyon, S.M. (2011). Dunbar's Number: Group Size and Brain Physiology in Humans Reexamined. American Anthropologist, 113(4), 557–568.

Friday, 14 November 2014

How Neurons Interact

The human brain is composed of several different types of cell, but the one that psychologists are primarily interested in is the neuron (nerve cell). There is a vast network of these cells in your brain - between 80 and 100 billion of them - and it is responsible for controlling every aspect of your behaviour.

A neuron. Image includes a close up of the synapse, i.e. the
connection with a neighbouring neuron. Source: here.

Of central importance to understanding these cells is the study of the way that they communicate with each other. When stimulated by neighbouring cells, each neuron sends out a small electrical current called an impulse. This travels along the nerve fibre, the 'axon', and then triggers the release of chemicals called neurotransmitters. These are then picked up by receptors on other cells.

This apparently simple process is the building block of all our psychological processes and behaviour.