Human-Computer Interaction Module 2.5

Question 1

This is the result of any action whose consequences are not what was intended by the person performing the action.

Answer 1

Human Error

Question 2

Errors can be classified into ______ and _____ according to how they occur.

Answer 2

Slips and lapses, and mistakes

Question 3

These errors are found in skilled behavior – execution of procedures that the user has already learned.

Answer 3

Slips and lapses

Question 4

An error in execution of any learned procedure would be a. . . ?

Answer 4

slip

Question 5

Slips are distinguished from lapses by. . .

Answer 5

the source of the failure.

Question 6

This error is a failure of execution or control – for example, substituting one action for another one in the procedure.

Answer 6

Slip

Question 7

This error is a failure of memory – for example, forgetting the overall goal, or forgetting where you are in the procedure.

Answer 7

Lapse

Question 8

This error, on the other hand, is an error made in planning or rule application.

Answer 8

Mistake

Question 9

One framework for classifying cognitive behavior divides behavior into. . . ?

Answer 9

Skill-based, rule-based and knowledge-based

For notes:
(Mistakes are errors in rule-based or knowledge-based behavior; e.g., applying a rule in a situation where it shouldn’t apply, or using faulty reasoning.)

Question 10

Notes: Overall, slips and lapses, are more common than mistakes

Question 11

This type of slip occurs when a person starts executing one sequence of actions, but then veers off into another (usually more familiar) sequence that happened to start the same way.

Answer 11

A capture slip

For notes: (A good mental picture for this is that you’ve developed a mental groove from executing the same sequence of actions repeatedly, and this groove tends to capture other sequences that start the same way.)

Question 12

This type of slip occurs when two actions are very similar. The user intends to do one action, but accidentally substitutes the other.

Answer 12

Description Slip

For notes:( A classic example of a description error is reaching into the refrigerator for a carton of milk, but instead picking up a carton of orange juice and pouring it into your cereal. The actions for pouring milk in cereal and pouring juice in a glass are nearly identical – open fridge, pick up half-gallon carton, open it, pour– but the user’s mental description of the action to execute has substituted the orange juice for the milk.)

Question 13

NOTES (not questions):

Lapses are due to failures of memory, particularly the short-term memory that is managing the execution of a procedure. A loss of intention lapse happens when you start executing a procedure and forget your goal in the interim. For example, when you walk to another room to fetch something, and by the time you get there, you no longer remember what you wanted.

Question 14

Lapses can also happen because of ______, which disrupt short-term memory and make you lose track of your place in the interrupted procedure.

Answer 14

Interruptions

Question 15

Another common lapse happens when. . .?

Answer 15

your goal is actually satisfied in the middle of the procedure.

For notes: (The remaining steps are cleanup or shutdown subtasks, which you may forget because you’ve already discharged your original intention. For example, if an ATM machine gives you the cash first, you may walk away from it without taking your card, because your original goal was getting cash.)

Question 16

Another kind of error, clearly due to user interface, is a _______. _______ are states in which the same action has different meanings.

Answer 16

mode error; Modes

Question 17

This occurs when the user tries to invoke an action that doesn’t have the desired effect in the current mode.

Answer 17

Mode error

For notes:(Mode errors are generally slips)

Question 18

The slips and lapses we’ve discussed have a few features in common. First, the root cause of these errors is often _________

Answer 18

Inattention.

Question 19

In a computer interface, you can deal with capture errors by avoiding very common action sequences that have __________

Answer 19

identical prefixes.

Question 20

Description errors can be fought off by applying the. . .?

Answer 20

converse of the Consistency heuristic

For notes: different things should look and act different, so that it will be harder to make description errors between them.

Question 21

There are many ways to avoid or mitigate mode errors. __________ entirely is best, although not always possible.

Answer 21

Eliminating the modes

Question 22

Other solutions to avoid mode errors are. . . ?

Answer 22

spring-loaded or temporary modes.

Question 23

With this mode, the user has to do something active to stay in the alternate mode, essentially eliminating the chance that they’ll forget what mode they’re in.

Answer 23

spring-loaded

For notes: ( The Shift key is a spring-loaded version of the uppercase mode. Drag-and drop is another spring-loaded mode; you’re only dragging as long as you hold down the mouse button)

Question 24

These modes are similarly short-term. For example, in many graphics programs, when you select a drawing object like a rectangle or line from the palette, that drawing mode is active only for one mouse gesture. Once you’ve drawn one rectangle, the mode automatically reverts to ordinary pointer selection.

Answer 24

Temporary modes

Question 25

Finally, you can also mitigate the effects of mode errors by ______________ so that no two modes share any actions.

Answer 25

Designing action sets

Question 26

One way to avoid lapses in procedure execution is to ___________, so that users have fewer steps to potentially forget.

Answer 26

keep procedures short

(Striving for simplicity often does this as a side-effect.)

Question 27

It’s also helpful to put more obvious structure on the procedure, a technique called

Answer 27

dialog closure

For notes:(Action sequences should be designed with a beginning, a middle, and an end. For example, think about drag and drop: At the beginning, you press the mouse button and see the object picked up with your cursor. In the middle, you move the object across the screen towards your target, getting feedback that it’s coming along. At the end, you release the mouse button, and see the effects of the drop.)

Question 28

NOTES:

OTHER RULES FOR ERROR PREVENTION
Here are some other ways to prevent errors.

If a command is illegal in the current state of the interface – e.g., Copy is impossible if nothing is selected – then the command should be disabled (“grayed out”) so that it simply can’t be selected in the first place.

One way to prevent errors is to allow users to select rather type. Misspellings then become impossible. This attitude can be taken to an extreme, however, as shown in this example.

One reason why selection is better is that it reduces the user’s memory load. Command languages demand lots of knowledge in the head, while menus rely on knowledge in the world.

Any information needed by a task should be visible or otherwise accessible in the interface for that task. The interface shouldn’t depend on users to remember the email address they want to send mail to, or the product code for the product they want to buy. Relying too heavily on the user’s short-term memory will lead to errors.

Protect users’ work is an important value judgment: errors that lose or destroy the user’s work are the worst kind. It’s worth substantial engineering to prevent this from happening – implementing automatic save, undo, file version histories, etc.

Question 29

An unfortunately common strategy for error prevention is . . .?

Answer 29

the confirmation dialog, or “Are you sure?” dialog.

For notes:(t’s not a good approach, and should be used only sparingly, for several reasons: *Confirmation dialogs can substantially reduce the efficiency of the interface. In the example above, a confirmation dialog pops up whenever the user deletes something, forcing the user to make two button presses for every delete, instead of just one. )

Question 30

In general, _____________ is a far better solution than confirmation.

Answer 30

reversibility(i.e. undo)

Question 31

Before you try to write an error message. . . ?

Answer 31

stop and ask yourself whether it’s really necessary.

Question 32

Assuming you can’t design the error message out of the system, here are some guidelines for writing good ones.

Answer 32

Be precise and comprehensible

Question 33

your message should be constructive, not just reporting the error but helping the user correct it.

Answer 33

Suggest reasons and solutions

Question 34

This is the idea that in the give and take between the user and the system, the user should have ultimate control.

Answer 34

User control and freedom (a term coined by Jakob Nielsen)

Question 35

The simplest kind of user control is a _______– the ability to cancel an operation, even if it was something they asked for.

Answer 35

veto

Question 36

A ________is a specific kind of window, a design pattern used in a dialog.

Answer 36

dialog box

Question 37

This pattern is a familiar pattern for improving the learnability of a complex interaction, by structuring it as a step-by-step process, with each step in a dialog.

Answer 37

Wizard Design pattern

Question 38

This pattern lays out data objects in the main section of the window, and gives the user a set of tools for operating on the objects. In this case, the user controls the dialog, deciding which objects to select and which tools to pick up.

Answer 38

Center Stage Pattern

Question 39

Here’s an interesting problem related to who’s in control of the dialog. Many interfaces interrupt users with questions, like the dialog boxes shown here. If the answer is always the same, it’s clearly inefficient (and annoying) to keep asking the same question repeatedly – so many of these dialogs offer the option ______________.

Answer 39

Never Ask Me Again

Question 40

Editing is important. If the user is asked to provide any kind of data – whether it’s the name of an object, a list of email attachments, or the position of a rectangle – the interface should provide a way to go back and change what the user originally entered – rename the object, add or remove attachments, move around that rectangle some more. Data that is initialized by the user but can never again be touched will frustrate user control and freedom.

Answer 40

User Control Over Data

Question 41

Keep CRUD in mind:

Answer 41

if you can Create an object or data field, you should be able to Read, Update, and Delete it, too.

Question 42

If _______ is the most common answer for user control over dialog, then ______ is the most common answer to user control over data.

Answer 42

Cancel; Undo

Question 43

Human error is characterized by?

Answer 43

Inattention, similarity, frequency

Question 43

SUMMARY(FOR NOTES)

Human Error

Error include slips, lapses, mistakes
Human error is characterized by inattention, similarity, frequency

Design Principles
Prevent errors as much as possible
Write good error messages otherwise
Give user control over the dialog
At least veto power, every operation should have Cancel
Give user control over data
CRUD: Create, Read, Update, Delete

Support Undo
But it’s more complex than it seems.