Don't think about a white bear. What did you just see in your mind's eye? If the answer was "a white bear", you'll have grasped one of the problems facing public health officials in talking about the risks from the Covid-19 coronavirus.
The message most experts will want to convey is, naturally, "Don't panic". But it's almost impossible for humans to hear that instruction without its alarming echo: "Panic".
If Covid-19 turns into a global pandemic, as looks increasingly likely, this problem is going to crop up again and again. Doctors want to convey information that will help people limit their own risks and minimise the burden on health systems. At the same time, they worry that the very act of sharing information will encourage people to act as if they're in the grip of an emergency.
Take canned goods. Many public health experts would recommend that people keep well-stocked food and medicine cupboards at the moment. In the event of a serious pandemic, that will mean you're not forced out of the house too often, or left at the mercy of supply chains that may be damaged by illness in the workforce.
The best way to do this is probably to marginally upgrade your normal daily purchases - an extra pack of tissues here, one more bag of rice there - and build up a stockpile over a course of weeks.
That's clearly not what's happened in places where coronavirus is spreading, though. We've already seen a toilet paper heist in Hong Kong and panic-buying in orderly Singapore.
One obvious reason for this is that it's not all that hard to clear out a supermarket. Grocery stores typically have no more than two to four weeks of inventory on hand at any one time, and much of that will be held off-site. If everyone buys sufficient supplies to see themselves through an extra few weeks, it's not unlikely that you or someone you follow on Facebook is going to find some empty shelves, and take this as evidence that society's foundations are quaking.
The behaviour that leads to such shortages isn't necessarily irrational. If you think a horde of panic-buyers is about to descend on your local shops next week and leave them out of stock, the rational approach might be to do your own panic-buying first. Once everyone starts thinking that way, a stampede is all but inevitable.
How should we deal with this situation?
One lesson can be learned from the failure of China's initial response to Covid-19: treat the population like adults.
"Tell us everything, being very clear that this is a dynamic situation that could change," said Jacqueline Street, a research fellow in public health at the University of Wollongong in Australia.
"Don't just say our hospitals are prepared, say how our hospitals are prepared."
The more that information is shared - not just on confirmed cases and deaths, but on how many tests came back negative, and on which subgroups of the population are most and least at risk, for example - the more individuals will be able to make their own judgments about safety and act responsibly.
Another lesson: the only thing we have to fear is the fear of fear itself.
No public official wants to be accused of spreading alarm, but a measure of concern in the face of a novel pandemic infection is both justified and salutary. The small behavioural changes that will be needed to reduce risks from Covid-19 - more care over hand-washing and touching, staying away from major public events in countries where the disease is spreading - won't come unless people are alert to the risks of infection.
"Actual panic is quite rare in these situations," said Julie Leask, a professor of risk communication at the University of Sydney's nursing school.
"People are clearly very concerned, but a level of concern is, in a way, important for gaining good co-operation."
Despite the way things may look, if you spend a lot of time on social media, humanity isn't really one bad press conference away from descending into bloody anarchy. The situation isn't helped when our political leaders fail to prioritise pandemic preparedness - US President Donald Trump has repeatedly pushed to cut funding for the area - or to speak up in defence of ethnic-Chinese people at risk of prejudice.
But sharing timely information with the public; encouraging readiness; and putting a bit more pressure on supply chains now when they're best able to bear it - all of that is a better strategy than waiting and then sounding a red alert at the last minute.
At this point, the fear of coronavirus is probably spreading through the world's population even faster than the virus itself. That may not be a bad thing if it encourages behaviours that will slow down the outbreak.
A measure of fear may be not so much infecting our societies, as inoculating them.
No country should make the "fatal mistake" of assuming it will be spared the coronavirus, the World Health Organisation (WHO) said, as governments from Iran to Australia raced to contain the epidemic's rapid global spread.