A Cessna -- or other small private plane -- suddenly appeared in the minds of many people on 9/11 when they first heard the words, "Did you hear that a plane flew into one of the Trade Towers!?"
Even some commercial pilots who watched from a distance as that first plane hit the towers thought to themselves something along the lines of: "Could be a drunk, or a terrorist, or a deranged suicide, or instrument malfunction -- but it's a small private plane."
It is the natural tendency most of us may have to assume the least bad possible, given the terrible news we've just learned.
Psychologists have various terms for this, but they talk generally of it being a denial technique to minimize the trauma in a way that allows people to keep their "meaning system" intact amid a crisis.
Trauma, even feared future trauma, they say, tends to shatter the complex "meaning systems" each of us builds in our minds to make it possible to get through life -- our general presumptions about how things are.
Thus, denial is often initially a survival mechanism, they say. It can help you keep your act together long enough to begin to deal with the new reality.
During five years of covering climate change, this reporter has noticed many people quietly pushing beyond their initial denial as they catch their breath and get ready for the changing world that climate scientists have long warned us is already here.
I often still find myself being pulled back out of denial when I talk to yet another climate scientist.
Psychologists find it natural that we should have evolved brains that quickly put away painful thoughts, when it's helpful and possible to do so, in a way that allows us to get on with life.
One psychotherapist told a colleague who covers global warming that what he was feeling in response to all the worrisome news about global warming was not depression, as he'd thought, but grief.
Depression, said this expert, robs your energy, makes it hard to work, whereas this colleague had become more journalistically productive than ever. Grief -- for example, at the thought of the loss of 10 to 20 percent of Earth's species as the heat rises -- is an entirely different psychological phenomenon and relatively familiar to psychologists.
Edgar Allen Poe, America's great writer admired worldwide for his creation of new genres of psychological fiction (in addition to inventing the genres of both science fiction and the detective story out of thin air), wrote a psychological treatise thinly disguised as a short story entitled, "The Imp of the Perverse."
This "imp" is the impulse that Poe finds in us to sometimes feel compelled to do something precisely because we know we shouldn't -- as if the daring naughtiness of it has a deep grip on our need for excitement and drama.
Perhaps all the apocalyptic movies of late ("Knowing," "The Day After Tomorrow," "2012," "Apocalypto," "War of the Worlds," "Terminator") are somehow Hollywood's response to a growing need in us to see the horrors of runaway global warming that scientists say we risk if we don't act.
We know we can't wait to see what it would be like, for then it would be too late to stop it -- but paradoxically, we often can't help but wonder about the horror we know we must prevent.