Just as the thoughts we have about a situation can affect our emotions and physical state, so too can our physical state and emotions affect our thinking.

When people are feeling negative emotions they are more likely to think negative thoughts. Thinking negative thoughts, in turn, intensifies the negative emotions and the body’s physical response.

Diagram of physical response, emotions and thoughts


A basic understanding of the workings of the brain can help us to understand why this is so.

Let us imagine the scenario of a woman who is sitting at home reading late one night when suddenly she hears a loud noise.

The sounds waves will hit the woman’s ear drums and will trigger a signal to be sent by her nervous system to her thalamus. The thalamus will send the signal to both her amygdala and the part of her neocortex responsible for hearing. The signal will reach her amygdala first which scans for potential danger without the ability to analyse. The human brain is hard wired to recognise loud noises as signifying potential threats and even tiny babies will startle to loud noise.

The amygdala will start to activate the stress response, including priming the muscles, and the woman jumps before her neocortex has even recognised that she has heard a sound.
Her neocortex will begin to analyse where the noise has come from and the possible causes for the noise to assess whether it is likely to be a benign cause such as a gate banging in the wind or a threatening cause such as a burglar.

Meanwhile her amygdala and hippocampus are quickly scanning for memories of similar noise. If they are not able to confirm that the noise is innocuous the amygdala will start to release a chemical called dopamine which focuses her brain’s attention on receiving any further information about the threat.

The amygdala will also release a chemical called noradrenaline which put the brain into a state of alert. The woman’s sympathetic nervous system will be activated to prepare her for action. Her heart rate increases and she starts to feel fear.

These changes tend to lead to reduced activity her neocortex, the part of the brain responsible for logical reasoning, making it harder for her to think rationally. She may fall into the trap of emotional reasoning and believe that because she feels afraid something bad is about to happen.

She hears a window smash and is so focused on the thought that she is in danger that she is now unable to think of an innocent reason for this occurrence. She grabs a large, heavy ornament to throw at the intruder. She does not stop to consider whether this is the best course of action and doesn’t worry about the consequences of hurting someone else because her ability to empathise and problem solve are reduced due to the fact that her amygdala has taken charge and her neocortex is struggling to keep up.

She is just about to hurl the ornament when she hears a ‘meow’ from the windowsill and realises that the window is not, in fact broken. The sound of smashing glass was the cat knocking over a milk bottle and there is no intruder after all.

The woman’s physical and emotional response to a perceived threat hijacked her ability to think logically because of reduced activity in her neocortex.

It is this change which explains why we can struggle to think straight and communicate well when we are stressed and why we may be more irritable with others.