Lecture 8 - Chapter 6: Change Blindness and Eye Witnesses

Change Blindness

• Phenomenon of visual perception

  • What you are perceiving Infront of you. Not what actually happened

  • Happens a lot in legal settings

    • Things move quick so you miss the obvious

• Stimulus changes without it being noticed by the observer

  • Significant change in the environment that’s not notices

Methods Used to Study Change Blindness

• Saccade-Contingent Changes

• Flicker Paradigm

• Film Clips/Real-Life Interactions

Saccade-Contingent Changes

• Movement going from one focal point to the next

• New information is excluded from processing during motion

  • can’t see change

  • supposed to give us a sense of stability in the visual world

• Rapid eye movement

• There is a time where you can’t see a change happening

• Its an intentional task - told them to expect change

McConkie & Currie (1996)

• Given practice photos and told them the type of changes that could've happened

• Although they practiced they missed a lot of things that they missed

What are Cognitive Factors that influence change detection?

• Meaningfulness of the Image

  • more likely to know the difference if it means something to you

• Visual Imagery Skills

  • you actually can detect the differences looking at the photos

• Instructions

  • if told, youll notice differences more

Flicker Paradigm

• Blank display between two matched photos (fraction of a second)

• Told to expect a change

• Timed until they notice the change

• The shorter the blank interference the less change blindness there is

  • More likely to notice the change

• The Longer the blank interference the More change blindness there is

  • More likely to not notice the change

• its an intentional Task - told them to expect change

Humphreys, Hodsell and Campbell (2005)

• saw pictures of a group of 4 women

  • different races (2 were white and 2 were Indian)

• Changes in Indian faces detected more quickly by indian participants

• same pattern found for white faces and white participants

Cross Race Identification Effect

• Can better recognize differences in face with people of the same race instead of strangers of a different races

Intentional Encoding Tasks

• participants are told to expect a change and are tasked with noticing when the change happens and what it is

Incidental Encoding

• participants are not told specifically that there will be a change

• instead tested on whether they notice the change occurring at all

Informed to Expect Change

• self explanatory

• your told what to expect dumb bitch

Change Probability Effect

• Changes are easier to detect when they are expected

Film Clips/Real-Life Interactions

• Incorporate realistic elements instead of computer or still images

• Researchers manipulate moving people/objects

  • changes can be missed with central, attended to objects/people

  • most likely to not occur ouside of a experiment

• Incidental Encoding - not told, figure it out

• relevant to eyewitness testimony

  • uses real moving people

Levin and Simons (1998) - Task

• Experimenter dresses as a construction worker

• Approach students on campus & ask for directions

• 2 confederates dressed as construction workers carry a door & interrupt

• One confederate switches with experimenter & continues conversation

Levin and Simons (1998) - Results

• 4/12 participants noticed the switch

• People are more likely to notice changes within their in-group (students) and less likely to detect differences in members of an out-group (construction worker)

  • They thought the construction worker was the same despite the switch as they werent focusing on his features

    • social factors could be important in change blindness.

Unconscious Transference

• Transfer of one persons identity to that of another person from a different setting, time or context

• relevant to eyewitness cases

Illusion of Continuity

• when two individuals are seen in close temporal and spatial proximity

  • in a way that one might assume that the two individuals are a single person

• occurs because human minds have expectations about how the world works

  • including expectations that motions are continuous

  • e.g if we see an object moving toward an obstruction, and then that object disappears behind the obstruction, we expect that object to appear again on the other side of the obstruction

Inattentional Blindness

• Failure to see an unexpected object that one may be looking at directly when one’s attention is elsewhere

• fail to detect unexpected salient objects that are in their visual fields

• seeing is different than percieving

Difference btwn Change and Inattentional Blindness

• Inattentional

  • The thing that changes comes and goes while youre paying attention to something else

  • e.g focusing on basketball players/ amount of passes and you miss the stupid monkey

• Change

  • thing that your focusing on changes and stays the same

  • e.g watching a man get up to answer the phone and in the next clip its a different man (levin & Simons)

Methods used to study Inattentional Blindness

• Visual Array Task - lab settings

• Lifelike visual situations - staged events

Visual Array Task

• present target array of items

• after short interval, show items again

• participant decides if anything has changed

Lifelike Visual Situations

• Simon and Chabris - stupid monkey experiment

  • the gorilla is the lifelike thing

• not seeing an object is not the result of not looking at that object

Memmert (2006)

• Tracked children’s eye movements watching the dumb gorilla video

• Children who failed to notice gorilla, spent as much time
  looking at it as those who noticed gorilla

• Seeing is different from perceiving

  • found that not seeing an object is not necessarily a result of not looking at that object.

Attention Capture

• what a shock - its shit that captures your attention

• the inverse of inattentional blind- ness.

Clifasefi, Takarangi & Bergman (2006)

Group A: told Alcohol/got Alcohol and Group B: told Alcohol/got Placebo
Group C: told Placebo/got Alcohol and Group D: told Placebo/got Placebo

• After all groups saw the edited version gorilla clip

• Rate the extent they experienced cognitive/physiological effects

Clifasefi, Takarangi & Bergman (2006) Results

• Intoxicated subjects: more likely to show ‘inattentional blindness’

• A third of all participants noticed the gorilla amongst the basketball players

• Intoxicated participants noticed the gorilla only 18% of the time

• Sober participants noticed it 46% of the time

• Witnesses could be less likely to experience weapon focus

  • slower to notice weapon in their visual field

Cross-Paradigm Research

a method that involves using multiple research paradigms or perspectives to study a subject.

Davis & Hine (2007) - Learning Phase

• combined Change bllindness and eyewitness testimony paradigms

• participants watch a burglary video

  • intentional condition (grp 1): told they were completing a memory test after

  • Incidental condition (grp 2): told they were completing watching a safety video

• Identify if the burglar changed halfway - neither group told this info

Davis & Hine (2007) - Testing Phase

• Completed questionnaire about content of the video

  • asked: Did you notice anything unusual about the burglar?

  • they had to Pick burglar from a lineup

Davis & Hine (2007) - Results

• 39% of participants noticed the change of actors, majority was from intentional
  condition (26 of 31)

• 49 participants who failed to notice the change

  • none picked both burglars from the lineup

• Intentional group recalled more details from the video

• Participants who noticed the change did better on the lineup task

Davis & Hine (2007) - Implications

• “witnesses may confuse an offender seen entering a building with an innocent person seen leaving it later.”

• Link between eyewitness & change blindness

• Poor accuracy of eyewitnesses can show for unfamiliar people seen in brief
  encounters