1. Simons and Chabris (1999) Area: Theme:

3. KEY TERMS:
Change blindness is where individuals do not detect large changes to objects and scenes from one view to the next.
Inattentional blindness occurs when attention is diverted to another object or task and observers often fail to perceive an unexpected object, even if it occurs at the point of fixation.

4. Background:
As we know, for us to detect changes in something which occurs, our attention is required. Previous research has looked at individual’s ability to focus on one stimuli only and detect changes in the ignored stimuli.
Aim:
The aim of this study is to test if inattentional blindness occurs in a realistic, complex situation.

5. Method Laboratory IMD IV: Transparent umbrella Opaque umbrella
There were four task conditions:
White/Easy
White/Hard
Black/Easy
Black/Hard
Therefore 16 conditions
Laboratory
IMD
IV:
Transparent umbrella
Opaque umbrella
Transparent gorilla
Opaque gorilla

6. Transparent
Opaque

7. DV = the number who noticed the unexpected event which was either the umbrella woman, or the gorilla.
Sample:
228 volunteers
Mostly students, referred to as ‘observers’
Given large candy bar or small fee for participation
36 participants data was removed. This led to 16 groups of 12 individuals

8. The videos:
Each participant was shown one of four videos. Each video…
Lasted 75 seconds long
Showed two teams of three players
One team wearing all white shirts
One team wearing all black shirts
Each team passed around an orange basket ball in a standardised order
Players also dribbled and made various movements

9. After 44-48 seconds of action, an unexpected event occurred for 5 seconds
In the umbrella condition, a tall woman holding an open umbrella walked from one side of the action to the other (left to right)
In the gorilla condition, a shorter woman wearing a full body gorilla costume walked through the action in the same way
In both conditions, all players continued to play as normal, before, during and after.

10. Procedure:
Participants were individually tested and each gave informed consent
Participants were told they would be watching two teams of three players passing basket balls. They were instructed to pay attention to the white or black team. The participants were asked to count the number of passes (easy condition) or the number of bounce passes made (hard condition)
Following this task participants were asked some additional questions - Did you notice anything unusual in the video? Did you notice anything other than the six players? Did you see a gorilla/woman carrying an umbrella walk across the screen?
Further details were asked for if they answered yes. They were also asked if they had taken part in a similar study or had heard of this phenomenon; if this was the case their results were removed. Debriefing then took place. 

11. Results:
Overall, 54% of participants noticed the unexpected event and 46% did not.
67% of participants noticed the unexpected event in the opaque condition, compared to only 42% in the transparent condition.
More participants noticed the unexpected event in the easy condition compared to the hard condition – 64% vs 45%.
While the effect of task difficulty was greater in the transparent condition, the Umbrella Woman was noticed more often than the Gorilla overall (65% versus 44%).
Results from the controlled observation were that only 50% noticed the event (roughly the same as the percentage that noticed the normal Opaque/Gorilla walking event (42%) under the same task conditions).

12. Conclusions:
Individuals do have inattentional blindness for dynamic events.
They will often fail to notice a seemingly obvious, but unexpected event if they are engaged in another monitoring task.
The extent of inattentional blindness is dependent on the difficulty of the primary task.
We are more likely to notice unexpected events if these events are visually similar to the events we are paying attention to.
Without attention we have no conscious perception – objects can pass through the spatial extent of attentional focus, but still not be ‘seen’ if they are not attended to.