2

If you want to stop an unintentional action, physical barriers are the most effective solution. You can't open a locked gate without unlocking it, or accidentally push a button with a safety cover.

But I wonder what the best approach is for times when you can't control the environment, or putting strong controls in place is inconvenient or impractical. We can only warn people that getting body wash in their eyes will hurt. Attaching a pair of goggles to every bottle and verifying they're in place before dispensing is just not feasible.

Specifically, is there any freely available research into the relative effectiveness of phrases to prevent an unintentional action such as "do not do this", versus "only do it this way", versus "avoid doing that", versus "if you do this a bad thing will happen"?

  • The most effective signs I've seen are graphical in nature with text as support. E.g. a picture of body wash applied to the hand with a checkmark and a picture of getting liquid into an eye with a slash across. – nightning Nov 30 '15 at 19:47
4

I've got no numbers for you or anything, but I do recall that negative words are often forgotten.

So instead of saying "do not put soap in eyes", phrase it as "keep soap out of eyes".

1

My first thought was to avoid direct negative orders, to give a clear warning or alarm message to get attention, and tell them the exact danger.

WARNING!

Coffee is scalding hot!

... and put it in their hands.

Drink at your own risk!

Then I thought maybe giving them an alternative action would be a little better.

Drink with caution!

Or if necessary, really drive home what is going to happen if they don't heed the warning.

Drink with caution or RISK INJURY!

Then I found this article I think you'll find interesting. I did and I'm not familiar with the field haha. Goes into the factors that impact whether people will listen and respond to your attempt to have them avoid unintentional action.

1. Cost of Compliance: your target has a goal. You aim to get them to comply with a different aim that may directly prevent or delay their desire. Make the cost low for them provide an alternative (add one of those monopoly tags to the cup to distract them momentarily and cool the coffee), reduce any extra effort (make sure the font is big enough that vision-impaired don't have to find their glasses to read their coffee).

[Note here: by saying "no" or "don't" (drink this delicious coffee right now) is a direct order AGAINST their only current goal. This makes compliance real low. So I think avoiding those negative command words is a good choice in certain situations that don't cross into legal or life-and-death situations. ]

2. Danger Perception: sloppy or hard-to-read print communicates lower danger, avoid the familiarization effect (we see "caution" everywhere, so it becomes background noise and doesn't register). One way to combat that is hangs up the design color, wording, etc somewhat regularly.

3. Decision Making: the article hits on risk-taking and social factors. One interesting mention is "Partial Compliance," where the person gets over the first hurdle (sees and understands accurately that something is extremely dangerous. But then he tries to mitigate the risk by performing the action in a way he deems "safe." In my dumb example, he might take the lid off and blow briefly, then take a sip and burn his lip. In the real world, it leads to pool diving accidents and car vs train tragedies.

0

In my experience telling people not to do something makes it an almost certainty that a good percentage will do it. Don't hit big red button!!!.

You hit it didn't you?

Anecdotally I have found that explaining the consequence of an action is more powerful than trying to modify behaviour. Extending @PixelSnader example you would end up with 'getting soap in your eyes will hurt like f**k'.

There is no direct negative language that would be ignored (do not put...) and you are not telling someone what to do (keep soap out...) rather you are giving timely and pertinent information and allowing the person using your interface to control what actually happens (all good interaction design advice). Well informed people make better decisions and idiots will find a way to do bad things regardless of your intensions.

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