Human%20Factors%20Psychology

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Human Factors Psychology

• Aside on Affordances

PSY-4340/PSY-5340, Dr. William Langston, MTSU
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Example 1

• Consider this example
• (Downloaded from http//sunburn.stanford.edu/nick
  /compdocs/, click on Practical HI Examples.pdf)

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Example 2

• Someone sent me a list of things like this
• Tescos Tiramisu Dessert
• Do not turn upside down (printed on the bottom of
  the box).
• Unrelated, but my favorite
• Japanese food processor
• Not to be used for the other use.

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Example 3

• Youve seen this one before.
• (Downloaded from http//www.baddesigns.com)

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Examples 4 5

• Two more from the same source.
• (Downloaded from http//ww.baddesigns.com)

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Affordances

• What do all of these have in common? I would
  argue that they all afford an action that isnt
  intended.
• Gibson (e.g., 1950) proposed a theory of direct
  perception. A caricature
• Light is structured into an ambient optic array.
  Each point in this array carries potential
  information.
• This information takes the form of affordances if
  a particular organism happens to be there to pick
  it up.
• Information pick-up is direct.

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Affordances

• Perceiving affordances
• If Im looking for a place to sit,
  sit-on-ableness will be perceived by me in
  objects that have that property. If I need
  something to throw, that will be afforded.
• Its kind of like an automatic process in that
  there isnt conscious mediation. The affordance
  is just there.

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Affordances

• Evidence
• Warren (1984) had people look at various
  configurations of stairs to rate climbability.
• Theres an optimal configuration for minimum
  energy expenditure, people preferred stairs that
  fit this configuration.
• People could accurately perceive climbability
  (based on a biomechanical model) from looking at
  the stairs.

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Affordances

• The implication
• When people are interacting with a
  machine/device, what it affords will have a big
  impact on what they do.
• Our examples
• A pull handle affords pulling, not pushing.
• A label affords reading. (I know its a
  stretch.)
• A urinal shaped device affords pee-in-ableness.
• A drawer handle affords pulling.
• A path affords walking (even if its not
  explicit).

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Affordances

• Why now?
• In the context of controls, I think there are
  important relations between design and
  affordances.
• Things you push should look like things to push,
  etc. (watch me work a new shower).
• There could be a high level interaction. If my
  goal is to turn it down, a control that affords
  pull-down-ableness is more likely to hit me than
  an arbitrary control.
• Remember that affordances are a function of the
  users body. If something is supposed to afford
  a particular action, it needs to be designed for
  all possible users.
• Im sure we could do more.

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References

• Warren, W. H., Jr. (1984). Perceiving
  affordances Visual guidance of stair climbing.
  Journal of Experimental Psychology Human
  Perception and Performance, 10, 683-703.