If you asked someone how much toilet paper they have in their home right now, I’m sure they could accurately tell you.

Did we ever think we would see a day when supermarkets would impose buying restrictions on toilet paper? It seems ridiculous, right? But the past few days have seen nervous customers panic-buying essential items such as toilet paper, canned goods and rice, leaving supermarket shelves bare. Some stores have even sold out of pet food and kitty litter.

As two behavioural scientists, we’d both heard about toilet paper being sold out but largely dismissed it as a passing anomaly. But upon visiting a local supermarket, sure enough, the shelves were empty.

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Neither of us had intended to get caught up in the hype but then asked each other ... if there was a packet left or if we happened to be there when they were restocking the shelves, would we have bought additional toilet paper? Of course we would. Why? Despite studying behaviour for years, our own reaction came as a surprise, especially since we both still had at least a week’s worth in our respective houses.

But, with further thought, the behaviour is largely explainable (behavioural scientists are very good at explaining behaviour after the fact!):

Why toilet paper?

It’s seen as an essential product, without ready substitutes. In many ways, toilet paper is similar to essential services. Imagine that the water utility told you they were cutting off the water in your neighbourhood for an undetermined period. I’m sure there’d be a surge in water tank sales and that baths, sinks and buckets would be filled.

Toilet paper is easily stockpiled and doesn’t deteriorate. It’s relatively a low cost/low risk investment and even if you have stockpiled, it’s something you will eventually use. Given we’re aware of people in quarantine for two weeks or longer, it makes sense to stockpile non-perishables in case this happens in Australia.

We hate missing out so when things are rare, particularly things we need, we chase them

In light of the first two reasons, buying toilet paper is an action that people can take now. The media (especially social media) may have made people feel helpless about the imminent arrival of Covid-19.

The virus has all the characteristics that make it scary – it’s novel, invisible, we have no control, we are involuntarily exposed to the risk, it makes us feel dread and we are personally vulnerable. As box ticking goes, this one is right up there.

While there is some guidance on what individuals can do about it (thorough hand washing and avoiding people), the media reminds us continually of the relentless path. Buying toilet paper alleviates some of this anxiety and helps us regain control.

Why has the panic spread and what drives the stockpiling frenzy?

Social media amplifies the fear which, in some way, seems to travel faster than the virus. The hashtags #toiletpapercrisis and #toiletpapergate were trending on Twitter. Seeing image after image of empty shelves sends signals to the public that this is an important issue everyone is talking about. What’s key to understand here is that media typically serves as a surveillance function, alerting us to risks that we need to shield ourselves from.

The supermarket shelf itself also sends signals. Toilet paper is bulky and, as it’s removed, the shelves look empty quickly, which triggers the perceptions of scarcity. In reality, the situation appears worse than it actually is.

We psychologically respond to scarcity. We hate missing out so when things are rare, particularly things we need, we chase them. Emotions can play a powerful role here. We’ve all been in a situation where we’ve missed out on something we thought we should buy, and felt remorse. In behavioural sciences, this is known as anticipated regret and, if you can get people to feel it, it’s a powerful motivator. By making the purchase, in some small way we protect ourselves from this feeling of regret.

Humans are finely attuned to monitoring what everybody else is doing (even subconsciously). Most of us use “what other people do” as a mental shortcut to decide on what the appropriate behaviour would be if we are unsure. It’s a simple decision mechanism called “social proof heuristic”, a concept popularised by psychologist Robert Cialdini. For instance, we litter more when the surrounding environment is littered, because it signals to us that littering is the norm. Hotel guests are also more likely to reuse their towels if told that “the majority of guests reuse their towels”. So, when we see people stockpiling toilet paper, the natural reaction is to do the same. Social proof can help decide how to act, or reassure us that we are taking the right action.

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We use this same principle of social proof when judging risk. Think of a situation where you hear an alarm go off. Most of us will instantly look around to see what others are doing, and to decide whether this is something to be taken seriously. If everyone reacts then we will tend to do the same.

Experts and governments have been telling us about pandemic preparedness, we’ve been urged to prepare as the widespread message has been that health systems across the world will struggle to cope. Everything gives the signal to prepare. So is anyone surprised when we see people panic-buying essentials?

There are at least three factors driving our response – scarcity, social proof, and regaining a sense of control. It’s scary how strong these influences are on our behaviour. Stockpiling is not needed, yet we still have the urge to do it. As behavioural researchers, we intimately know the forces acting on us, yet we’re helpless to resist them.

• Professor Liam Smith is the director of BehaviourWorks Australia, Monash Sustainable Development Institute

• Dr Celine Klemm is a research fellow at BehaviourWorks Australia