Designers usually make many assumptions about users’ familiarity with the technology, and the way they might use the product in the real world.

According to a Survey by

” 92% of respondents checked social media on the phone in the past month, 31% stayed in the bathroom longer than necessary to finish activity on their phone “

But do we take account of these scenarios during the design of our digital products? Not likely right ? Which means that some design decisions turn out to be wrong when the product gets into the hands of actual users which arises due to some unanticipated user behaviors.

All conceivable human behavior cannot be catered for and there will be some just too bizarre to ever anticipate and fix. But there are certain types of error that can be predicted and, to some extent, designed for, to ensure the user experience isn’t compromised too much by their occurrence.

Errors happen and unintended actions are inevitable.

They are a common occurrence in usability tests and are the result of problems in an product design / interface and imperfect human actions and It is valuable to have some idea about what these are, how frequently they occur, and how severe their impact is.

Don Norman has written extensively about slips and mistakes in The Design of Everyday Things and can be categorized into 2 broad causes of human errors.


Slips are the classic unintended action a user makes while trying to do something on an interface even though the goal is correct (e.g., a typo).


Mistakes are made when users have goals that are inappropriate for the current problem or task; even if they take the right steps to complete their goals, the steps will result in an error.

The image shown above is a classic example of slip

Slips often happen when users are quite familiar with the goal that they seek to achieve and with the procedure for accomplishing that goal, but accidentally they take the wrong step when trying to achieve it. Often, when executing tasks that are well practiced, we tend to allocate fewer attentional resources, and, as a result, we can “slip” and perform the wrong action. Thus, ironically, slip-type mistakes often are made by expert users who are very familiar with the process at hand; unlike new users who are still learning how to use the system, experts feel that they have mastered the task and need to pay less attention to its actual completion.

Strategies for preventing slips are centered around gently guiding users so that they stay on the right path and have fewer chances of slipping. Assist users by providing the needed level of precision, and encourage users to check for errors.

How to avoid Unconscious Slips ?

a. Include Helpful Constraints :

While it’s not always a good idea to limit users’ choices, in cases where there are clear rules that define acceptable options, it can be a good strategy to constrain the types of input or a specific way to perform a tasks. In this classic case including a handle bar to constraint user for using it in a very specific way.

Choose Good Defaults:

Use Real Data During Prototyping:

When we design with real data, we make more informed design decisions, knowing fully well the constraints and edge cases that could likely break our design during implementation. This makes us take further considerations into how we design our layouts, navigations, modules and interaction patterns.


Slips are common errors that happen when users do not pay full attention to a task or have small memory lapses. Preventing errors of this type is largely a matter of reducing burdens on users and guiding them when precision is required by using design patterns that communicate how they work to users.

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