Looking for a HCI term for when a system has several modes of operation

Question

I'm looking for a term which I'm pretty convinced exists but I have forgotten. Roughly, it describes the fact that a system or tool has several modes of operation / states and behaves differently in either of them. For instance, a document editor can be in read-only and normal states.

I remember having been advised in HCI and ergonomics courses to avoid designing systems or tools that will behave differently depending on the mode or state they're in. It may be that I don't remember so well and that the advice was specifically about behaving unexpectedly because of "statefulness". For instance, my document editor's Print function should behave the same in read-only and normal modes. Does anyone have examples of good or bad applications of "statefulness" that provided good UX or caused usability issues?

If I wanted to give myself a general design guideline with regard to "statefulness", I would want to prevent the states in which a system can be from causing interaction breakdowns by influencing how the user should interact with the system, without the user being aware of the state. Hence, general guidelines that can be applied to decide if a specific incarnation of "statefulness" is likely to be nefarious to users are also welcome!

Thanks.

Answer 1

The term that you're referring to is called, unsurprisingly, MODE :)

Mode

It's a long-standing concept in HCI and UX, being criticized from very early on by several design and usability gurus, including Don Norman and Jef Raskin.

As this Wikipedia article defines it:

In user interface design, a mode is a distinct setting within a computer program or any physical machine interface, in which the same user input will produce perceived different results than it would in other settings.

The best-known modal interface components are probably the Caps lock and Insert keys on the standard computer keyboard, both of which put the user's typing into a different mode after being pressed, then return it to the regular mode after being re-pressed.

Mode errors

In the book "The Humane Interface, New Directions for Designing Interactive Systems", Raskin wrote:

Modes are a significant source of errors, confusion, unnecessary restrictions, and complexity in interfaces.

According to Don Norman, the reason is

... because they limit the user's freedom to act (only certain actions are possible in each mode). Also, modes often lead to user errors because the user forgets what the current mode is and initiates actions that might have had the intended effect in some other mode but lead to problems when the computer interprets them under the rules for the active mode.

This article gives the definition and examples of mode errors:

(Mode error is) a type of slip where a user performs an action appropriate to one situation in another situation, common in software with multiple modes. Examples include drawing software, where a user tries to use one drawing tool as if it were another (e.g. brushing with the Fill tool), or text editors with both a command mode and an insert mode, where a user accidentally types commands and ends up inserting text.

Design guidelines

As for guidelines, the seminal Don Norman's 1983 paper lists three ways to minimize mode errors:

1. Do not have modes
2. Modes should be clearly marked and should be properly placed on the interface to avoid confusion
3. Make sure commands required by different modes are not the same, so that a command issued in the wrong mode won't make any big problem

Hope it helps.

Answer 2

To answer part of the question, the classic example of a 'mode' error was the ease of accidentally putting a wordprocessor into "overtype mode" so that rather than inserting text into existing text it would happily overwrite the existing text.

As it was something that nobody did deliberately it was very difficult for a user to sort out why the wordprocessor had changed how it operated and how they were going to get it to work again normally:

http://en.wikipedia.org/wiki/Insert_key