1

During testing of a website, we found an unexpected behavior when the user misses a target and, due to a very slight mouse movement while clicking (i.e. accidentally dragging the mouse 1 pixel to the side), the opposite action is triggered, which is very disturbing.

I would like to reference some UX heuristics/guidelines to convince the developers this is a bad pattern, in the hopes that this will better explain them why such design is not good, so that future iterations of the website will converge faster.

However, the closest heuristic I found related to the subject would be this one:

Error prevention: Even better than good error messages is a careful design which prevents a problem from occurring in the first place. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to the action.

But I am not sure this communicates the situation clearly. In particular, the unwanted triggered action is not necessarily an error, and the "confirmation option" certainly does not apply.

The overall idea is that no action is better than possibly wrong action.

If the user really wants to trigger the behavior, they only need to repeat it with a larger intensity. As in smartphones, when a slight drag does nothing, and you have to drag it a decent amount before it actually does something.

Is there a more specific heuristic/guideline that would apply here?

  • If your developers need convincing that missing a target by one pixel does the opposite of what was intended instead of nothing, then the best thing to give them is a P45 (for those not in the UK, it's the tax-form you get when you leave a job or are fired). – TripeHound Feb 1 '18 at 11:28
  • If you've user tested then I hope you have video evidence of the sessions. You should show your developers this. – colmcq Feb 1 '18 at 11:39
  • The website is being outsourced to another company. I don't know how well-formed their developers are, so I mostly wanted to find some sort of general helpful advice and guiding principles to give them, so that I won't have to say things like "here we need to disable this action if the movement is less than 5 pixels". – anol Feb 1 '18 at 13:22
1

Well, the heuristic "error prevention" is a rule of thumb in general. The application of the heuristic is not limited to what the description tells. In your case it is a user error that could easily be prevented. Maybe you can substantiate the heuristic with use of the ISO 9126 specification, and in particular the usability part.

From the Product quality model:

usability
degree to which a product or system can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use
Note 1 to entry: Adapted from ISO 9241-210.
Note 2 to entry: Usability can either be specified or measured as a product quality characteristic in terms of its subcharacteristics, or specified or measured directly by measures that are a subset of quality in use.

operability
degree to which a product or system has attributes that make it easy to operate and control
Note 1 to entry: Operability corresponds to controllability, (operator) error tolerance and conformity with user expectations as defined in ISO 9241-110.

user error protection
degree to which a system protects users against making errors

From the quality in use model:

satisfaction
degree to which user needs are satisfied when a product or system is used in a specified context of use
Note 1 to entry: For a user who does not directly interact with the product or system, only purpose accomplishment and trust are relevant.
Note 2 to entry: Satisfaction is the user’s response to interaction with the product or system, and includes attitudes towards use of the product.

Source https://www.iso.org/obp/ui/#iso:std:35733:en

  • 1
    Thanks for the references, but they seem a little too legalese and not some sort of "practical heuristics" to give to outsourced web developers who likely didn't have much training in terms of usability. I don't intend to sue or cancel the contract, just to give some "helpful advice" that is likely to prevent them from saying "here, it's fixed, now you need to move 2 pixels instead of 1". Which would end up with me having to find out exactly how many pixels to take into account, and over-specify it for them. – anol Feb 1 '18 at 13:20
  • I'm sorry to tell but that was exactly my point. Your situation is very specific and it is inescapable that you need to inform the developers about your quality standards. But you can use the test results to show the problem and the required minimal adjustments needed to prevent users from such errors. – jazZRo Feb 1 '18 at 16:53
1

no action is better than possibly wrong action.

I don't think this helps communicate the situation.

In the context you described, the user is interacting with the system by moving the mouse cursor toward some target. Action is implicit, therefore, the correct action is better than the wrong action.

During testing of a website, we found an unexpected behavior when the user misses a target and, due to a very slight mouse movement while clicking (i.e. accidentally dragging the mouse 1 pixel to the side), the opposite action is triggered, which is very disturbing.

You are describing a defect - a shortcoming, a flaw, a blind spot. The current UI design (or the code listening to the interaction events) makes it too easy for the user to get an undesirable result. An improved design would preclude users' triggering opposite actions with just a 1-pixel mouse movement.

Designing with that in mind is just applying good practice and common sense. As @jazZRo explained, Jakob Nielsen and the ISO folks and probably many others have already abstracted this in a way that it can be applied to all kinds of design. Those are the correct references.

Whether you're doing the design or you're outsourcing it, start with common good rules of thumb and you may find fewer unexpected behaviors when you test it with users.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.