Simons & Chabris

• Background: What is visual attention?

  • People tend to believe that what they see preserves the richness of their visual experience

  Change blindness – observers fail to notice large changes to objects from one view to the next, particularly if those objects are not the centre of interest

  Inattentional blindness – observers fail to perceive the unexpected object when attention is diverted to another object or task
• Background: How is visual attention studied?

  • Static visual displays (visual version of dichotic listening)
  • Dynamic visual displays:Neisser - “The Umbrella Woman”:
  • Ppts watched video of a team passing a ball and a woman carrying an open umbrella walks across the screen 30 seconds in – only 48% noticed (inattentional blindness)
• What were the aims?

  • To build upon previous research and investigate factors that may affect visual detection rate

  1.        Visual similarity of unexpected object and attended ones

  2.        Task difficulty

  3.        Superimposed version of display vs live version

  4.        Nature of unusual event
• What was the design?

  • Lab experiment
  • Independent measures

  IVs (16 conditions):

  Unexpected event – umbrella woman or gorilla

  Film – transparent or opaque

  Task – easy or hard

  Participant followed – black or white team
• What was the sample?

  • Self selected
  • 228 undergraduate students from America (observers)
  • Rewarded through a candy bar

  Final analysis:

  • 192 ppts equally distributed across 16 conditions

   

  • 36 ruled out as they knew about the phenomenon
  • Further 12 ppts took part in controlled observation
• What were the materials?

  • 4 video tapes of 2 teams throwing a basketball
  • Each tape lasted 75 seconds
  • 2 teams and 3 players in each
  • Showed players passing ball
  • After 44-48 seconds unexpected event occurred lasting 5 seconds
  • Woman walked from left to right holding umbrella or wearing a gorilla costume
  • 2 styles (superimposed) or opaque (all actors filmed at same time)
• Procedure: What did they do?

  • Tested individually
  • Observers told to watch either black or white team
  • Told to keep silent mental count of total number of passes made by the attended team (easy) or total number of bounce and aerial passes made by the attended team (hard)
  • Immediately after viewing, observers asked to write their counts
  • Then asked surprise series of questions to determine if they noticed the unexpected event
• Procedure: What questions were asked afterwards?

  1. Did you notice anything unusual?

  2. Did you notice anything other than 6 players?     (Order of questions rules out social desirability)

  3. Did you see anyone else?

  4. Did you see the gorilla / woman carrying and umbrella walk across?

  • If they answered yes their details were asked for
  • Afterwards they were also asked if they had previously participated in a similar experiment or heard of similar experiments and they were discarded if answered yes (rules out demand characteristics)
• Procedure: What ethical considerations were there?

  • Gave informed consent in advance and at the end each observer was debriefed by replaying the video tape
• What were the results?

  • 54% of observers did notice the unexpected event
  • The umbrella woman was noticed more, showing she was more visually distinctive
  • Unexpected event noticed more in the opaque version
  • Unexpected event noticed more in the easy condition
  • Observers more likely to notice the gorilla when watching the black team
  • Little difference between those noticing the umbrella woman between observers watching the black or white team
• What were the conclusions?

  • Results show sustained inattentional blindness for dynamic events (extends Neisser)

  Factors that lead to inattentional blindness:

  • Difficulty of primary task – if more difficult there is more inattentional blindness
  • Observers less likely to notice events if the event is dissimilar to events they are paying attention to
  • There is no conscious perception without attention