HOW DESIGNERS THINK

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HOW DESIGNERS THINK
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Empirically-Based Studies

• surveys
• direct observation (in situ)
• direct observation (input-output models)
• protocol analysis

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Protocol Analysis data from verbal utterances

• Recording method
• Concurrent method Record actions and think-aloud
  concurrently
• Retrospective method Record actions and after
  session completed record verbalisation
• Analysis method
• Process-oriented analysis
• Content-oriented analysis

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Protocol Analysis

• Video and audio taping
• Transcription
• Code development
• Coding
• Analysis

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Coding Method
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Coding Scheme for Design Processes
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Process Information About Designing

• How much time is spent doing what?
• What is the distribution of the time of
  activities over a design session?
• What differences are there between experts and
  novices?
• Experiment
• Conceptual design tasks
• Novice graduate designers
• Designers with more than 5 years experience
• Think aloud method
• Process-oriented analysis
• Present typical results only

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Time spent drawing for a novice circuit designer
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Total time spent reasoning about Function and
Behaviorvs Total time spent reasoning about
Structure Novice
Function Behaviour
Structure
100
75
of Total Time Spent in Category
50
25
0
0
25
50
75
100
Time As a Percentage of the Total Time Taken
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Total time spent reasoning about Function and
Behaviorvs Total time spent reasoning about
Structure Expert
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Asimows Model of Designing

• analysis
• synthesis
• evaluation

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Empirical Testing of Asimows Model
Evaluation -gt Reformulation
Evaluation -gt Synthesis
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Revised Asimow Model
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Distribution of Activities - Expert
50
45
40
35
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Percentage of Total Time
25
20
15
10
5
0
Pa
Ev
Ju
Ca
An
Ps
Cl
Re
Dd
Co
Pp
La
Lb
Ka
Kd
Ds
Activity Code
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Distribution of Activities - Novice
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Spectral Distribution of Events
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Fixation

• Fixation exposure to an existing design has
  effect on current designing
• pictorial representation of a possible design
• pictured design uses principles that are part of
  the knowledge base of the discipline

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Experiment

• Subjects
• Final year mechanical engineering students
• Final year industrial design students

Design Task

• Device for assisting the elderly in getting into
  and out of a bath

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Experimental Design

• Two groups from each discipline
• One group given the verbal instructions
• One group given the verbal instructions and the
  picture of the example design

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Significant Superficial Features

• Fixed to base plate
• Rigid boom
• Orientation to bath as in example
• Tiles on side of bath as in example
• Fixed to bolted base plate
• Moulded seat with back
• Perforated seat

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Discussion

• Fixation occurred differently with mechanical
  engineers and industrial designers
• Fixation occurred with analogical and superficial
  features
• Appropriate and inappropriate fixation
• Multiple examples and fixation
• Multiple examples and innovation

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EXPERTS VS NOVICES

• Case study of an expert and a novice architect
• Expert appears to be 2.8 times as productive as
  novice
• What might be the causes?

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Protocol Studies of Expert and Novice Designer

• Same design task
• Retrospective protocol
• Suwa-Gero-Purcell coding scheme
• Content-oriented analysis

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Sketches by Expert
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Sketches by Novice
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Suwa-Gero-Purcell Coding Scheme

• D-action draw
• M-action moving without drawing
• L-action look at existing depictions
• P-action perceive visual/spatial features of
  existing depictions
• F-action attach meanings, concepts or functional
  issues to existing depictions
• G-action set-up of goals

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Primary Action Codes
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Secondary Actions
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Primary Concurrent Actions Correlated with
Depicting Drawings
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Secondary Concurrent Actions Correlated with
Depicting Drawings
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Structures of Concurrent Actions Correlated with
Depicting Drawings
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Structures of Concurrent Actions Correlated with
Depicting Drawings
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Conclusions

• Differences between expert and novice
• Productivity
• Rate of cognitive activity
• Structure of concurrent actions
• Strategic knowledge

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Strategic Knowledge

• Expert chunks knowledge into 7 /- 2 concurrent
  actions (Millers magic number for human short
  term memory capacity)
• Novice chunks knowledge into up to 15 concurrent
  actions this fails Millers magic number test
• Strategic knowledge may be thought of as
  successful chunks that have been developed
  through interactions with the task