A user error is an error made by the human user of a complex system, usually a computer system, in interacting with it. Although the term is sometimes used by human-computer interaction practitioners, the more formal human error term is used in the context of human reliability.
User error and related phrases such as PEBKAC ("Problem Exists Between Keyboard And Chair"), ID-10T error ("Idiot error") and other similar terms are also used as slang in technical circles with potentially derogatory meaning. This usage implies a lack of computer savvy, asserting that problems arising when using a device are the fault of the user. Critics of the term argue that the problems are caused instead by a device that doesn't take into account human limitations and is thus designed in a way that induces errors.
The term can also be used for non-computer-related mistakes.
Joel Spolsky points out that users usually do not pay full attention to the computer system while using it. He suggests to compensate for this to make usable systems, thus allowing a higher percentage of users to complete tasks without errors:
If you sit down a group of average users with your program and ask them all to complete this task, then the more usable your program is, the higher the percentage of users that will be able to successfully create a web photo album. To be scientific about it, imagine 100 real world users. They are not necessarily familiar with computers. They have many diverse talents, but some of them distinctly do not have talents in the computer area. Some of them are being distracted while they try to use your program. The phone is ringing. WHAT? The baby is crying. WHAT? And the cat keeps jumping on the desk and batting around the mouse. I CAN'T HEAR YOU!
Now, even without going through with this experiment, I can state with some confidence that some of the users will simply fail to complete the task, or will take an extraordinary amount of time doing it.
Experts in interaction design such as Alan Cooper believe this concept puts blame in the wrong place, the user, instead of blaming the error-inducing design and its failure to take into account human limitations. Bruce "Tog" Tognazzini describes an anecdote of Dilbert's creator Scott Adams losing a significant amount of work of comment moderation at his blog due to a poorly constructed application that conveyed a wrong mental model, even though the user took explicit care to preserve the data.
Don't think of the user as making errors; think of the actions as approximations of what is desired.
Acronyms and other names
|Look up PEBCAK in Wiktionary, the free dictionary.|
Several terms like PEBKAC or and ID10T error are often used by tech support operators and computer experts to describe a user error as a problem that is attributed to the user's ignorance instead of a software or hardware malfunction. These phrases are used as a humorous way to describe user errors. A highly popularized example of this is a user mistaking their CD-ROM tray for a cupholder, or a user looking for the "any key". However, any variety of stupidity or ignorance-induced problems can be described as user errors.
Phrases used by the tech-savvy to mean that a problem is caused entirely by the fault of the user include PEBKAC (an acronym for "Problem Exists Between Keyboard And Chair", also PEBCAK or PBKAC), POBCAK (a U.S. government/military acronym for "Problem Occurs Between Chair And Keyboard"), PICNIC  ("Problem in Chair; Not in Computer") and EBKAC ("Error between keyboard and chair").
ID-Ten-T error (also seen as ID10T and ID107) is a masked jab at the user: when ID-Ten-T is spelled out it becomes ID10T ("IDIOT"). It is also known as a "Ten-T error" or "ID:10T error". The UserFriendly comic strip presented this usage in a cartoon on 11 February 1999.
In United States Navy and Army slang, the term has a similar meaning, though it's pronounced differently:
- The Navy pronounces ID10T as "Eye Dee Ten Tango".
- The Army pronounces 1D10T as "One Delta Ten Tango".
The networking administrators' version is referring to the cause of a problem as a "layer 8 issue".
The computing jargon refers to "wetware bugs" as the user is considered part of the system, in a hardware/software/wetware layering.
The automotive repair persons' version is referring to the cause of a problem as a "faulty steering actuator," "loose nut between the steering wheel and the seat," or, more simply, "loose nut behind the wheel." Similarly, typewriter repair people used to refer to "a loose nut behind the keyboard" or a "defective keyboard controller."
The broadcast engineering or amateur radio version is referred to as a "short between the headphones". Another term used in public safety 2-way radio (i.e. police, fire, ambulance, etc.) is a "defective PTT button actuator".
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