When we compliment someone, or do something that could be considered ‘nice’ for them, the only response we are likely to see is the smile on their face or, if we’re lucky, maybe a hug. Behind the scenes however, within the brain, there is a whole lot more going down – for the giver and the receiver.

Largely, you can thank activity in the ventromedial prefrontal cortex (vmPFC) for this. The vmPFC generally refers to an interconnected network of regions in the lower medial and orbital prefrontal cortices, the intricacies of which are not important for our considerations in this case. For our purposes, the vmPFC is an area of the brain that plays a role in mood regulation and social interaction.

Richard D. Lane et el (1997) conducted studies using Positron Emission Tomography (more commonly known as PET scanning!) to measure regional brain activity during periods of heightened emotion – they used film and memory recall to evoke several emotions including happiness, sadness and empathy. During this experiment, happiness was found to be associated with increased activity in the thalamus and vmPFC.

But how does the above happen? It isn’t magic, although it could be considered pretty close as far as I’m concerned.

Within the brain, we have small molecules known as neurotransmitters – these are the chemical messengers of the brain, in that they allow communications between two neurons that are not physically connected by transmitting the message across a gap known as the synapse. At the synapse, function is very much like a relay race – one event causes another event to start, which then stimulates the next event.

Receiving, or indeed giving, a compliment causes the pre-synaptic neuron to become ‘active’ – activity in this neuron is generated by something known as an action potential, or impulse, running along the length of it. The impulse is an explosion of electrical activity in the neuron, caused by sodium ions (which have a positive charge – Na+) rushing into it, giving it a positive charge.

Neurotransmitters are stored in vesicles in the pre-synaptic neuron. When the action potential reaches them, calcium channels are opened; this allows calcium (Ca2+) to rush into the neuron.

This influx of calcium ions triggers a series of events, which ultimately results in the release of the neurotransmitter from a storage vesicle into the synaptic cleft.

Once in the cleft, the transmitters will bind to the specific receptors on the post-synaptic neuron – the Sodium channels here are ligand gated, meaning they open when the receptors are bound to, and the resulting influx of Na+ ions generates an action potential. It is this action potential, and associated activity in the vmPFC, that is thought to contribute to positive emotions.

Each neurotransmitter does have a different job though. For example:

• Oxytocin – this is widely known as the bonding hormone, as it is released during periods of closeness to another individual; it is associated with trust, loyalty and decreased pain perception.
• Serotonin (or 5-hydroxytryptamine/5-HT) – this is the neurotransmitter most widely acknowledged in the pathology of mood disorders; higher levels of free serotonin are associated with increased self-esteem, perceived worthiness and a sense of belonging.
  
• Dopamine – this handy neurotransmitter is responsible for pleasure seeking and reward-driven behaviour; both receiving and giving compliments can elicit a response that increases levels of dopamine transmission in the brain.

A small act of kindness from you can mean an influx of oxytocin, dopamine AND serotonin in the brain of the receiver. It is widely accepted that neurotransmitters, particularly Serotonin, have a huge role to play in mental health; whether this is a best friend or stranger, a simple compliment or hug can make a HUGE difference to psychology, and therefore quality of life.

If you act of kindness is felt, the responsive smile is also believed to work as a tool to make you feel happier also; neuroscience says that it is almost as thought you are experiencing the emotion for yourself, as the same areas of the brain are activated.

So what is the take home message?

In a nutshell: be kind. Encourage kindness, show kindness and welcome acts of kindness with open arms – you can really never know what a difference you may make.