TORONTO -- As humans, our ability to assess risk and make decisions is largely based on emotion, which may explain why some people are more concerned about the potential risks associated with vaccines than coming down with COVID-19.

In their recommendations on the AstraZeneca vaccine, the National Advisory Committee on Immunization (NACI) told Canadians to consider their own personal risk factors when deciding on which vaccine to take.

But psychologists say assessing risk isn’t that simple and that people rely heavily on emotions when making decisions.

“If you're in a positive mood, versus a negative mood you may have a different belief about how likely good or bad outcomes are,” Ross Otto, assistant professor in the department of psychology at McGill University, told in a phone interview on Wednesday.

Paul Slovic, psychology professor at the University of Oregon, notes that it’s hard work to do the analysis required for risk assessment, which is why we often turn to emotion to determine risk.

“The human brain is lazy and if we think we can do the job easier, we'll go that route. And there is an easier route, and that's to use our gut feelings,” Slovic told in a video interview on Wednesday.

That may sound like people are behaving on a whim, but Slovic says it’s how we get through our every day, not by checks and balances and calculating risks on a notepad.

For Otto, the focus is: what information first comes to mind when assessing a risk?

He said that compared to death rates from accidental injuries, the risk of death from COVID-19 is much lower but weighs far more heavily in our thoughts.

“Why is it so salient in our minds?” he said.

Complicating matters further when Canadians are trying to assess the risks of contracting COVID-19 in their daily lives is that public health directives don’t always give explicit instructions.

“There are guidelines about what you can and can't do in public, but none of them say ‘don't,” Otto said.

Our experience also plays a role in our decisions.

“We learn from experience, so our feelings are shaped in part by our experience,” said Slovic. “So if we do something and nothing bad happens we think it's less risky.”

Our lack of control over COVID-19 and its consequences make matters even worse.

“If you have the belief that you have no control over the outcome, you might stop viewing anything as a choice you can take,” Otto said.

And it’s not just our own personal control that changes risk perception.

“One of the factors that led either to higher or lower perception of risk was control, either your own personal control, or your sense of the degree to which the authorities knew enough about it and could control it,” said Slovic.

He likens it to slicing a loaf of bread. When you’re in control of the knife, you can bring it quite close to the fingers on the hand stabilizing the loaf. However, if someone else was wielding the knife while you held the loaf, you might not want the knife close to your fingers.

This lack of control could be what is making people more hesitant to get the AstraZeneca or Johnson & Johnson vaccines that, in very rare cases, have caused clotting.

“Once you get the shot. You can't control that risk at all,” he added.

Some people feel they have more control over their exposure and feel more comfortable taking the risk of waiting for a different vaccine.

These rare adverse effects of the vaccines are new to us, and as people get comfortable with a situation, the risk seems to dissolve with it.

“Novelty conveys a sense of riskiness to us,” said Slovic.

There’s also a sense of betrayal that people feel when the vaccine that is supposed to protect them and others instead causes harm, he said.

He likened it to the outrage and upset when airbags killed people in accidents. They were said to protect motorists, so drivers felt deceived in the rare instances that airbags deploying resulted in death. In Canada, between 1990 and 2000, eight people were killed as a result of airbags deploying. Compared to 2,548 deaths from car accidents in the year 2000 alone.

But, concerns over AstraZeneca and Johnson & Johnson vaccines comes down to our emotions being unable to do math and adjust accordingly, said Slovic.

“Your brain can’t multiply a feeling by a probability and get a reduced feeling,” he added.

In Canada, your chances of getting COVID-19 vary depending on a number of factors, including race and socio-economic status. But, according to Ontario’s COVID-19 Science Table, with variants of concern being the dominant strain causing infections, chances of hospitalization from the coronavirus is increased by 63 per cent, a 103 per cent increased risk of ICU admission and 56 per cent increased risk of death.

But when the most recent piece of information absorbed was about negative outcomes, it becomes difficult to ignore the negative emotions that bubble up at mention of the vaccines. With recent news of AstraZeneca and Johnson & Johnson vaccines focusing on the rare adverse effects, it can be hard to call other information to mind.

“So we tend to make a risk assessment based on what immediately comes to mind, what is immediately available,” Otto said.

All hope isn’t lost for those who may have already decided the risk of blood clot from the vaccines is too high.

“There's sizable literature showing that people can internalize and learn vicariously through the actions of others when they see the outcomes of what happened to a close other they'd be more likely to kind of follow suit.”

It might help some people to compare numbers to put things into perspective. In a given year, it’s more likely that you will be struck by lightning than develop blood clots from either the AstraZeneca or Johnson & Johnson vaccines.