Should UI be phrased positively or negatively? [duplicate]

Question

I was discussing with a workmate whether user interfaces should be phrased in a positive or a negative manner. I've observed positive sentences are clearer than negative ones to the average user.

I've heard some discussions on this matter and most people seem to agree that phrasing positively yields better results in user experience than negative ones. But is there a UX recommendation on this?

EDIT:

to be clearer: should I notify my user that his/her input data is invalid by saying "input is invalid" or "input is not valid"? Or does it not affect UX at all?

Is it better to negate a positive verb or use a verb that has a negative meaning in itself?

Answer 1

UI error messages should be direct, objective statements which the user only has to read once to understand.

I personally perceive zero differences between input is invalid and input is not valid

^ However if I came across either of those messages then I would immediately assume the programmer was too lazy to tell me what was invalid and now I have to go on a wild goose chase.

What I perceive as good messages:

• Digits only please
• Email is not valid
  • Go one step further and say something like only one @ symbol allowed
  • Or list out valid email chars
• 6 character minimum
• 3 characters to go
• Please use m/d/yyyy format here
• Max Qty.: 3 - If you need more then give us a call right now (555-555-5555)

Answer 2

Realistically, "input is invalid" and "input is not valid" are the same. Neither is a negative frame of the other.

Typically, negative frames are not recommended, because the mind typically has to flip itself to understand the instruction. For example, "Don't think of an elephant" is an impossible instruction to follow.

In other words, you may accidentally elicit the opposite action from your user if you frame it negatively. Best to frame things positively, and with imperatives (i.e., "Do this") wherever possible.

Other examples:

"Don't click submit until you have filled out every field in the form" would be a silly thing to write at the top of your form. You'd probably get more people clicking submit before the form was fully filled out.

"Entry is invalid" does not tell me what I should do - it only tells me that what I did was wrong. How about: "You must enter a valid email address"

"Your password must not include the following characters: !^@$%))($" <--This may be necessary to state, but is really awful UX. It is easy to miss the "not" in that sentence. Best to let them use one and then with a validation/warning say "Your password may not include any of the following characters: !^@$%))($"

That being said, negative frames do have a place - and it usually involves inhibiting an expected action:

"Don't use the back button!" "Do not refresh the page!"

But these MUST come with an imperative, positive statement of what to do instead. It is also good to include a reasoning behind the warning.