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How do people use an Interface

Lecture # 4

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User Interface Design?Design is solving a problemDesign is creating an object or the means to

enable, in our case a user, to achieve an intentTo optimize our solution we need to understand

how people interact with the world

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Human ActionIntent

Plan

Act

Assess

Refine/Stop

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Norman’s Activity ModelDon Norman (1988) proposed that users view the

user-interface as a mean to an endThe interface, according to Norman’s model

provides users with the mechanisms to achieve something that they desire or want

This mechanism includes 2 basic elements An Interface – The means used to communicates

between the user and application what needs to be done

Interaction – The mechanism by which the user is expected to achieve the tasks using the interface

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User Interface DesignFor the example below

The interface includes:The blue iconMessageLabeled button

The interaction includes:Reading the messageClicking on the close button

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The Action ModelThe action model deals with the interactionIt suggests that the way people act can be

decomposed into:An IntentionA PlanAn action An Evaluation

Actions are performed within a context of a higher level goal

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Example – Removing The Error Message

To remove the error message (Goal) the Activity Model hypothesizes that user willFormulate an intent to close the messageView the box and decide that to close it one needs

to click on the close buttonClick on the “Close” buttonCheck to make sure that the dialog box

is indeed closed

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Activity ModelGoal

External World

Execution Gap

Evaluation GapHow do I (the user) affect the state of the world

Was the change that I sensed the same as what I expected

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Gulf of ExecutionDeals with the gap between what the user wants

to do – Intention and the action needed to implement the intentHow do I start my carHow do I save a documentHow do I set the time on my car clock

The role of the user interface is to help bridge this gap by helping users determe how to act

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Gulf of EvaluationDeals with the gap between perception and

interpretationDid my car started?Was my document saved?Am I controlling the time on my car clock?

The role of the user interface is to help user determine what happened in the real world

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Implementing the ActionFor the user Interface to be effective it will need

to assist users in helping them Execution

Form an intentionPlan out the action – how will it flowExecute the plan

EvaluationPerceive the result Interpret the resultEvaluate the result

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Form an intention

Plan out the action Execute the plan

Perceive the result

Interpret the result

Evaluate the result

Veering to the Left of the Road

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Closing the GapsHelping the user cross the chasm

Goal

Intention

Detailed Plan

Comparison

Interpretation

Perception

External World

Execution

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Example - Execution• Forming a Goal• I want to inform my team about a meeting I had.

• Intention to Act• I have outlook open on my desktop. I will set up a meeting

for the team and myself. I will open a meeting invitation

• Planning the Action• I need to move the cursor to the meeting icon and click on

it

• Executing the Action• I move the cursor to the meeting icon and I click on it

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Example - Evaluation• Feedback from the Action• A meeting set up form is opened

• Interpret the Feedback• I am now able able to specify a meeting and invite Sean

• Evaluate the Outcome• Positive – I’m able to start scheduling a meeting. No

further action is needed• Negative – The form I opened is for scheduling an

appointment not a meeting• The Action Cycle is either repeated or a new goal is

formed

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Example – Planning Challenge

From Michael J. Darnell @ http://www.baddesigns.com/

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Example – Planning Challenge

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Example – Execution Challenge

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Example – Interpretation Challenge

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So what are the the implication of this model for design?