Simons & Chabris

• Background

  Divided attention is the condition of paying attention to more than one stimulus.
• Background

  Focused visual attention: the cluttered scenes of everyday life present more objects than an individual can respond towards simultaneously, and often more than can be fully perceived at any one time.
• Background

  If we are not focusing on something, we will not notice if it changes. This is known as change blindness.
• Background

  Individuals perceive and remember only those objects and details that receive focused attention.
• Background

  Inattentional blindness is when attention is diverted to another object or task, so observers often fail to perceive an unexpected object, even if it appears at fixation.
• Aim

  To examine inattentional blindness for complex objects and events in dynamic (active) scenes.
• Aim

  Previous research did not investigate the role of task difficultly in detection, and no direct comparisons were made between performance with a superimposed version of the display and a live version. This research therefore expands previous research into inattentional blindness, by investigating these further factors.
• Sample

  • 228 participants (referred to as "observers")
  • Almost all were undergraduate students
  • 36 participants' results were discarded so results from 192 participants were used
• Sample

  • 192 participants' data was used from across 16 conditions
• Sample

  Each participant either volunteered to participate:

  • Without compensation
  • For a large candy bar
  • For a single fee (for participating in a larger testing session including another, unrelated experiment)
• Research Method

  It was a laboratory experiment
• Research Method

  It used an independent measures design.
• Research Method

  The independent variables were whether the participant took part in:

  1. the transparent/ umbrella woman condition
  2. the transparent/ gorilla condition
  3. the opaque/ umbrella woman condition
  4. the opaque/ gorilla condition
• Research Method

  For each of the four displays there were four task conditions:

  1. white/ easy
  2. white/ hard
  3. black/ easy
  4. black/ hard
• Research Method

  The dependent variable was the number of participants in each of the 16 conditions who noticed the unexpected event (Umbrella woman or Gorilla).
• Materials

  • There were four video tapes.
  • Each was 75 seconds long
  • Each showed two teams of three players (one in white shirts, one in black shirts).
• Materials

  • Players moved around in a relatively random fashion in an open area in front of a bank of three elevator doors.
  • The members of each team passed a standard orange basketball to one another in a standardised order.
• Materials

  • Passes were either aerial or bounce.
• Materials

  • Players would dribble the ball, wave their arms and make other movements consistent with their overall pattern of action.
• Materials

  • After 44- 48 seconds of action, either of two unexpected events would occur.
  • In the Umbrella woman condition, a tall woman carrying an open umbrella moved from off camera left to off camera right.
  • In the Gorilla condition, a shorter woman wearing a gorilla costume which fully covered her body moved through the action in a similar way.
  • Both unexpected events lasted 5 seconds.
  • Play continued during and after the unexpected event.
• Materials

  • The two styles of video were transparent and opaque.
  • In the transparent condition, the white team, black team and unexpected event were filmed separately. The three video streams were rendered partially transparent and superimposed using digital video-editing software.
• Materials

  • The two styles of video were transparent and opaque.
  • In the opaque condition, all 7 actors were filmed simultaneously and could thus occlude (block out) one another and the basketballs. This required some rehearsing to avoid collisions and other accidents, and to achieve natural looking patterns of movement.
• Procedure

  • 21 experimenters tested the participants.
  • To ensure standardisation of procedures, a written protocol was devised and reviewed with the experimenters before data collection was begun.
• Procedure

  • All participants were tested individually.
  • They gave informed consent before taking part.
• Procedure

  • Before watching the tape, participants were told they would be watching two teams of basketball players passing basketballs and that they would pay attention to one of the teams (either black or white).
• Procedure

  Participants were told to either:

  • keep a silent mental count of the total number of passes made by the attended team (easy condition)

  OR

  • keep a separate silent mental count of the number of bounce passes and aerial passes made by the attended team (hard condition)
• Procedure

  After viewing the video tape and performing the monitoring task, participants were immediately asked to write down their counts on paper. They were then asked the following questions:

  1. While you were doing the counting, did you notice anything unusual in the video?
  2. Did you notice anything other than the 6 players?
  3. Did you see a gorilla/ woman carrying an umbrella walk across the screen?
• Procedure

  • If any participants answered yes to any of the questions after the videos, they were asked to provide details about what they noticed.
  • If at any point they mentioned the unexpected event, the remaining questions were skipped.
  • After questioning, participants were asked if they had previously participated in a similar experiment, heard of such an experiment or the general phenomenon. If they answered yes, their data was discarded.
• Results

  • Out of all 192 participants across all conditions, 54% noticed the unexpected event and 46% failed to notice the unexpected event.
• Results

  • More participants noticed the unexpected event in the Easy condition (64%) than the Hard condition (45%).
• Results

  • The umbrella woman was noticed more often than the gorilla overall (65% versus 44%).
• Results

  • the gorilla was noticed by more participants who attended to the actions of the black team (58%) than those who watched the white team (27%).
• Controlled observation

  • The researchers decided to carry out a further test using a controlled observation. This included a longer, more striking unexpected event.
• Controlled observation

  • In a separate opaque-style video recording, the gorilla walked from right to left into the live basketball-passing event, stopped in the middle of the players, thumped its chest, and then resumed walking across the screen. The gorilla's action lasted 9 seconds.
• Controlled observation

  • 12 participants watched this video.
  • They attended to white team and engaged in the easy monitoring task.
• Controlled observation

  • Only 50% of participants noticed the event (roughly the same as the 42% of participants who carried out the task in the same conditions in the first experiment).
  • This therefore confirms the findings from the experiment, showing external reliability.
• Result- Overall, 46% of participants failed to notice the unexpected event in their task (either a gorilla or a woman holding an umbrella walking through a basketball game) when counting the number of passes made.


  Conclusion- Individuals fail to notice an ongoing but unexpected event if they are engaged in a primary monitoring task.
• Result- More participants noticed the unexpected event in the easy task (64%) compared to the hard task (45%).


  Conclusion- The level of inattentional blindness depends on the difficulty of the primary monitoring task.