In 2019 in Nepal, a woman and her two sons accidentally suffocated in a windowless shed after being banished to a so-called period hut because she was menstruating. This practice, known as chhaupadi, was outlawed in Nepal many years ago but is still observed in some districts.

The custom rests on the belief that menstruation is impure. To quote from Wikipedia: ‘In this belief system, it is thought that if a menstruating woman touches a tree, it will never again bear fruit; if she consumes milk, the cow will not give any more milk...if she touches a man, he will be ill.”

It is easy, from a distance, to dismiss such beliefs as superstition. After all, none of these claims withstand even minimal testing. A single counterexample would be enough to weaken them, yet the beliefs persist because they are rarely, if ever, examined against reality.

However, the same process happens on a smaller scale in everyday life. Our minds make predictions about ourselves, others, and the world that go untested. We then behave as if they are facts, even when a simple experiment could show
otherwise.

Cognitive behavioural therapy (CBT) treats these predictions not as truths but as hypotheses to be tested, as ideas to be examined, not obeyed. One of its most useful tools in this regard is the behavioural experiment. It is exactly what it sounds like: approaching your fears the way a scientist approaches a puzzling phenomenon, with curiosity rather than certainty.

Health anxiety

The Oxford Guide to Behavioural Experiments in Cognitive Therapy, a guide for CBT clinicians, gives the example of Heather, who had a 10-year history of health anxiety and who was fixating on a lump in her neck which she feared was cancer. Her belief that any symptom indicated serious illness was strong. She believed she needed to be hyper-vigilant about physical things or she might miss something serious.

The alternative perspective was that focusing attention on a symptom or self-monitoring can blow it out of proportion and make her anxiety worse. However, Heather believed if she didn’t pay attention to the symptom, she would miss something important. ‘I will feel more anxious because I am not keeping a check on it’, she said. ‘I won’t be able to think about anything else.’

In a behavioural experiment, she alternated between days of checking the lump and focusing on it, and days of noticing the thoughts but resisting the urge to check. Her diary showed that on checking days, intrusive thoughts and anxiety were higher, while on non-checking days, both were lower. 

By the end, her conviction that she had cancer dropped significantly. Heather learned that her checking and hyper-focus were actually fuelling her anxiety and reinforcing her fears, and that resisting these urges allowed her to test and revise
her beliefs.

Another example from the same book: Mary, 56, who had experienced two heart attacks, struggled to say ‘no’ and felt like ‘everyone’s dustbin’, constantly prioritising others’ needs over her own. She feared that refusing requests would upset people and harm her relationships. 

In a behavioural experiment, she protected an hour of rest each day, telling her neighbour she was busy but offering a brief alternative meeting. Her neighbour was initially upset but later apologised and accepted the new boundary. Mary learned that she could assert herself without harming relationships and that prioritising her own needs was necessary for her
wellbeing.

Importantly, behavioural experiments do not aim to engineer success. They aim to test predictions. Even a difficult experience can disprove the original fear. The key is that you face the situation rather than avoid it, gather genuine evidence, and draw balanced conclusions.

Our beliefs feel powerful. However, they are still just beliefs, and they can be tested.

A behavioural experiment is a way of stepping out of the huts we sometimes find ourselves in, opening the door, and checking whether the world outside is as threatening as our minds might insist.
More often than not, it isn’t.