Hebbian theory is a theory in neuroscience which explains how groups of neurons adapt and grow in the brain. It rests on the assumption of neuroplasticity (the plastic, malleable and flexible nature of the brain). Neuroplasticity covers synaptic plasticity, which refers to the plastic nature of synaptic connections in the brain, as well as non-synaptic plasticity, which refers to the plastic nature of the axons, dendrites and cell body of the neurons. The brain is no longer viewed as a static organ, but as an organ which can change throughout a person’s life. Neuroplasticity plays a vital role in healthy development, learning and memory.
Hebbian theory is named after the neuroscientist Donald Hebb, who introduced the idea in his 1949 book, The Organisation of Behaviour. This theory, also known as Hebb’s rule, is summed up in the following way:
When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells such that A’s efficiency, as one of the cells firing B, is increased.
What this means that if two cells, or a group of cells in fact, repeatedly or persistently fire together, then they will be more likely to fire together.
This rule is often paraphrased as, “Cells that fire together, wire together.” Neurons which fire together results in more connections forming between them. However, this easy-to-remember phrase is somewhat oversimplified and should not be taken literally – cell A must fire just before cell B for this stronger relationship to form. It is important that cell A caused or took part in the firing of cell B for there to be an increase in synaptic strength.
Each time a group of neurons forms a causal relationship or pattern, their tendency to form that causal relationship or pattern in the future is increased. Of course, there is a downside to all of this plasticity. It makes our brains vulnerable to the wrong kind of patterns. Forming dysfunctional habits early on can create neural patterns which stick which continue to promote those habits. It’s a constant cycle. Moreover, if certain neural patterns are not used, then they become weak, following the rule of thumb: “If you don’t use it, you lose it”. Hebbian theory has been used as a mechanism to explain how patients with long-term depression find it so difficult, almost impossible, to escape their constant low mood and despondency.
But all hope is not lost. Hebbian theory can also be used to form the right kinds of connections – those which lead to healthy everyday functioning and behaviour. There are two important aspects of Hebbian theory which provide hope for anyone stuck in a rut, who just can’t seem to break their negative habits of thought and behaviour. The first aspect is that experience and environmental changes can modify existing synaptic connections, which in turn will have corresponding effects on one’s thoughts and behaviour. The second aspect is that many areas of the brain remain plastic well into adulthood. This challenges the long-held view that childhood represents a ‘critical period’ – the first few years – in which the child requires the appropriate stimulus for the development of certain skills. If these stimuli are not provided, then the child will find it very difficult, if not impossible, to develop these attributes later in life.
Evidence for the Critical Period Hypothesis is inconclusive. Proponents of it point to studies of child abuse and deprivation, in which children who are not taught their mother tongue in early years find it difficult to do so later in life. However, critics say that this difficult could also be explained by trauma. Proponents also claim that there is compelling evidence of a critical period for the acquisition of a second language. In a 1989 study by J.S. Johnson & E.L. Newport, it was found that young children are better at learning a second language than adults. On the other hand, research results show that adolescents and adults perform better under controlled conditions. It may appear that children can learn a second language more quickly and easily, but this is not entirely true. It is a misconception, based on the fact that children are usually better at pronunciation and because we are more tolerant of mistakes that they make.
In any case, regardless of whether Hebbian theory completely dispels the Critical Period Hypothesis, it at least shows that people will be able to change certain aspects of their personality well into adulthood. Furthermore, people can make these life changes by modifying their experiences and environment. This may seem to oversimplify things. After all, changing your personality is not just as easy as having new experiences or doing some travelling – it requires a high level of commitment and consistency. Let me explain.
First of all, there do appear to be core features of the personality, those which are largely immune to modification. These would include the personality traits, introversion and extraversion which were popularised by Swiss psychiatrist Carl Jung in his book Psychological Types (1921). Jung defined introversion as an “attitude-type characterised by orientation in life through subjective psychic contents” and extraversion as “an attitude type characterised by concentration of interest on the external object.” People normally generalise introverts as being quiet and unsociable and characterise extroverts as being noisy and sociable. But this isn’t entirely accurate.
No-one is a pure introvert or extrovert – their level of introversion or extraversion varies depending on genetics, environment, life experiences, and so on. Secondly, those who would be classified as more introverted than extroverted are not necessarily quiet and reclusive, it’s just that very stimulating social situations are more draining. Introverts need more alone time, time to re-charge, than do extroverts. This article examines the science behind introversion and extraversion. Psychologist Susan Cain’s book Quiet and her TED talk, The Power of Introverts (see the bottom of article for the video), has also successfully uncovered the systematic disadvantages that introverts face in society today.
Someone may, of course, be equally introverted and extroverted (ambiverted) and so can switch between these two opposing personality types. Furthermore, since no-one is a pure introvert or extrovert – although some people are more obviously one than the other – introverts can behave like an extrovert, and vice versa. That said, it is very difficult, if not impossible, for people to actually change their core personality types. I myself, for example, am very introverted and know that I always will be. The problem with education and the workplace, as Susan Cain highlights, is that it is designed for extroverts (i.e. with open planned offices, big teams, lots of team planning, and so on) and that introverts become drained and discontent as a result. Nonetheless, even though some parts of the personality cannot be radically changed, others can. There are many parts of the personality which are highly valuable, but which become stagnant through non-use or weak through infrequent use. But we can re-activate these aspects of ourselves and become much better people as a result.
According to a recent study, for example, the ‘Big Five’ elements of the personality do in fact change over time. These five elements are openness, conscientiousness, extraversion, agreeableness and neuroticism. These elements change in response to new life experiences that introduced over time (relationships, work, children, etc.). This seems almost obvious – of course, people change as they get older. However, whether we want to develop our positive personality traits – those contributing to our own well-being and to those of others – depends which experiences we choose and environments we want to put ourselves in. Another study found that people who joined the military also experienced shifts in their personality, with an overall decrease in their agreeableness.
So if we want to become more open and conscientious, then how would Hebbian theory assist in achieving this goal? As the military study demonstrates, it is persistent training which leads to long-lasting personality changes. What the training probably does is strengthen synaptic connections in some areas of the brain, whilst weakening others. Which connections or brain areas these would be I cannot say. But we do know is that there are certain areas of the brain which are involved in moral feelings, such as compassion. We also know that there are certain areas of the brain rich in ‘mirror neurons’, neurons which are said to be the biological basis of empathy. These neurons will fire simply when one is observing the action of another – they allow one to mentally rehearse an action, so it’s almost as if you are experiencing what someone else is experiencing.
A study published in Psychological Science, for example, found that people can be trained to be more compassionate and that this training involves corresponding changes in the brain. Participants were trained using ‘compassion meditation’, an ancient Buddhist technique designed to increase caring for people who are suffering. Practising ‘compassion meditation’ leads to heightened activity in the left prefrontal cortex, an area associated with feelings of joy and empathy. The neuroscientist Andrew Newberg also found that practising meditation is linked to becoming a more compassionate person in general. He writes about this in his book How God Changes the Brain. It is no coincidence that compassion is at the heart of Buddhist teaching. The supreme importance attached to this virtue must come down to the fact that Buddhists engage in meditation, a skill which encourages feelings of compassion.
You cannot become compassionate simply by resolving to become compassionate or determining to do so. You have to train yourself like in weight training. To achieve noticeable results, you have to train hard and train regularly. Meditation works because it involves a deep level of focus (on caring for others) and so probably has a greater impact on the relevant brain areas than simply caring about others as a passing thought. In addition, meditation works best in this regard when it is maintained as a habit. Focus plus persistence is what will give you the desired results. This sounds like self-help psycho-babble, but it’s true. And it makes sense from a Hebbian perspective – if you create a new habit of thought and behaviour, this will have corresponding effects on your brain. Neurons involved in compassion which fire together will wire together. Likewise, mirror neurons (involved in empathy) which fire together will wire together. You can then substitute “compassion” with any personality trait (agreeableness, openness, neuroticism etc.) which is subject to the same level of change.
Practising mindfulness meditation regularly can also allow long-term personality changes to occur. This form of meditation has been found to reduce stress in healthcare professionals (whose careers are very stressful) and in cancer patients. In healthy individuals, mindfulness meditation will help to alleviate the stresses of everyday life. This study investigated the neural correlates of anxiety and mindfulness meditations. The researchers found that meditating for 20 minutes could significantly reduce a healthy subject’s level of anxiety. Mindfulness meditation has also been very successful at reliably reducing rates of depression in individuals. From a Hebbian point of view, by constantly training your mind to be mindful of the present moment, you will be able to translate the experience of calmness during meditation into your daily life. By reducing your levels of stress, anxiety and depression on a regular basis, you will become a less stressed, anxious and depressed person and much more calm in the long term. Studies have confirmed that this is because of the corresponding changes that take place in the brain.
If you want to become a more moral person, then you should do more moral actions – an almost obvious statement. But that’s easier said than done. For example, let’s say £50 gets taken out of your bank account every month and goes towards your chosen charity. Have you become a moral person as a result? The consequences of that decision will probably be good and alleviate a certain level of suffering. However, I am not convinced that will necessarily lead to a positive personality change. I think that it is having good intentions which will be most likely to result in a deeper personality change.
The reason that it is so difficult to be a good person is that it is so difficult to have good intentions consistently. It is easy to give money away, but not so easy to give it away in a more meaningful and intentional way. Furthermore, I believe that actions which directly help others – if done on a regular basis – are more likely to re-activate brain areas responsible for compassion, empathy, altruism etc. Again, it is easy to throw change at the homeless, but not so easy to be genuinely concerned about their welfare. Our brain is like a muscle and can be trained to grow in certain areas that we see fit. If we modify our habits of thought and behaviour, this will modify the associated brain areas, which in turn will increase those habits. Of course, it’s common sense to say that to change yourself you have to change how you think and act, but what Hebbian theory tells us is that there is a deep physiological reason for thinking in this way.