Stress

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Stress Long-term memories

• Dr. Sophia King
• Rm. P24 HWB
• sk219_at_le.ac.uk
• http//www.le.ac.uk/pc/sk219/ps2011.html

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Memory and Emotion

• Memory can be influenced by emotions and mood
  states
• Moods as an internal context for memory,
  regardless of actual content of mood state
• Being in the same recall mood as testing mood
• Using mood as a filter to retrieve matching
  information
• The particular valence of certain emotions may
  have specific effects on our memories
• Negatively emotional or traumatic events
• Emotions as metal states that are linked to
  visceral physical responses Mandler (1992)
• Some aspect of value labelling of values
• Physical response

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Memory and Stress/Arousal

• When looking into specific types of emotions that
  may have an effect on memory, a great deal of
  work has looked at stress
• What is stress?
• Physical response Arousal (increased heart
  rate, skin conductance etc Duffy (1962) arousal
  as a continuum ranging from a coma state to full
  excitement)
• Value aspect/value label perceived as negative
  or unpleasant in nature (Mandler (1992) calls
  this the noxious nature of the stressful
  stimuli, and the desire to remove it)
• The situation by itself can be perceived as the
  stressor

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Investigating Memory and Arousal

• How good are memories for stressful events? In
  what ways can the potential effects of stress on
  memory be tested?
• Studies of Autobiographical memories
• General population studies
• Studies of samples with particularly traumatic
  experiences
• Field studies
• Eyewitness testimony
• Lab studies
• Controlled studies of detail recall in response
  to stressful and neutral stimuli

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Studies of Autobiographical memories

• Research into autobiographical memories revealed
  that certain vivid memories seemed to be
  remembered in great detail over time
• Flashbulb Memories a surprising and shocking
  event is remembered in great detail, even down to
  seemingly irrelevant details (Brown and Kulik
  1977)
• Pillemer (1984) tested participants memories for
  the attempted assassination of Reagan, once after
  one month, and once after six months. He found
  the two sets of recall to be highly consistent
  over the delay.
• Bohannon (1988) tested memories either two weeks
  or eight months after the Challenger explosion.
  The higher participants rated their emotional
  reaction to the explosion, the better their
  memories for the explosion

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Flashbulb memories

• Christianson, Carlsson, Fredriksson, Nilsson
  (1989)
• Investigated a Swedish samples memories for the
  assassination of their prime minister in 1986
• Asked participants for their strongest memory of
  the previous Saturday before testing, plus
  details about the time they learnt about the
  assassination
• Participants were re-tested a full year later.
  They were asked to describe in detail the event
  they had chosen from the Saturday before the
  first interview
• found a more dramatic decrease in detail memory
  for the control events than the assassination
  (60 remembered the details of the assassination
  attempt, versus just over ten percent for the
  other event)

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Flashbulb memories II

• If a flashbulb memory is retained at the level of
  detail of a photograph, then access to the
  details of the event should remain constant, is
  there special mechanism that forms these
  memories?
• Rubin and Kozin (1984)
• Events that are of personal rather than national
  importance are also remembered in great detail.
• They asked participants for their three most
  vivid memories for events,
• The majority reported a negative event such as an
  accident involving themselves or someone close to
  them.
• Bohannon (1988) found out the more the Challenger
  story had been rehearsed, the greater the level
  of recall

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Studies of Autobiographical memories

• Although the evidence doesnt seem to point to a
  special mechanism that create Flashbulb Memories,
  the evidence from these studies does seem to
  indicate improved recall
• Wessel Merckelbach (1994) the higher the
  emotional rating given to a remembered traumatic
  event, the more likely details from that event
  were remembered
• Wagenaar and Groeneweg (1990)
• Interviewed survivors of Nazi concentration
  camps, comparing these recent accounts to ones
  given by the same people 40 years earlier
• later memories still contained great detail about
  camp conditions and inmate mistreatment
• Witness G.H.V. had forgotten both that he had
  witnessed another inmates murder and the name of
  the murdering guard

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Field Studies of Traumatic Events

• Studies of Autobiographical memories often prove
  hard to verify (e.g. what someone was wearing at
  a particular time)
• Details reported may not be the result of
  encoding into memory, but reflect processes that
  occur after encoding
• One very useful area of research is the memories
  of eyewitnesses to crime.
• They provide excellent information about memories
  formed under times of stress
• Police records after the events provide ways to
  check the validity of the witnesses answers

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Memories of Crime Victims

• Kuehn (1974)
• Looked at victims of violent crimes police
  statements
• Most victims gave almost complete perpetrator
  descriptions
• Victims of crime which involved inflicted
  violence (e.g. rape or assault) gave more limited
  descriptions of their attackers than victims of
  robbery
• Yuille and Cutshall (1986)
• Interviewed 13 witnesses to a shooting incident 5
  months after the event, comparing these accounts
  to original police statements and reports
• Sixty percent of the material reported was new,
  but repeated information was highly consistent
  with the police statements.
• There were more errors when the witnesses were
  describing people and actions than when
  describing objects

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Memories of Crime Victims II

• Christianson and Hübinette (1993)
• Analysed the memories of twenty-two bank
  robberies by fifty-eight eyewitnesses
• Even after a substantial time interval memory for
  details was significantly more accurate for
  victims (i.e. bank tellers) than for bystanders
• Victims had better memory for both details of the
  robbery and the surrounding circumstances (such
  as information about date, day, time, and number
  of customers)
• Although memories for crime show impressive
  levels of detail, as the violence of the crime
  increases, memories seem to become impaired

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Weapon Focus

• In certain situations of high stress subsequent
  perpetrator description is impaired.
• Christianson and Nilssons (1984) woman who was
  sexually assaulted and could not recall the event
  for several months after it happened
• Weapon focus (Loftus, Loftus, Messo 1987)
  when a weapon captures the attention of the
  witness resulting in a reduced ability to recall
  other details from the environment
• Loftus, et al. (1987) showed participants two
  series of slides of events in a bank, identical
  except for a critical slide, (showing either a
  gun being pointed at a teller, or a cheque being
  handed over). Participants made more, longer eye
  fixations on the gun
• In a line-up memory test on the protagonist,
  participants in the weapon condition remembered
  significantly fewer items than the cheque
  condition

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Weapon Focus II

• Pickel (1998)
• Showed participants videos of staged interactions
  between two people
• During the interactions participants saw one of
  three objects being held up towards a person
  neutral (a wallet), threatening (a pair of
  scissors) and unusual (a raw chicken)
• She found the same pattern of impaired recall
  when the object was highly unusual as when it was
  a weapon
• Weapon Focus seems to combine the threatening
  nature of an object with how unusual it is
  perceived as being by the onlooker

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Laboratory Studies of Detail Recall

• Laboratory based studies of memory for stressful
  stimuli afford a greater degree of control than
  field studies. The disadvantage to this method is
  the reduced levels of stress that can be invoked
  in volunteer participants
• Stress is normally evoked in the lab using
• Gory/violent pictures
• Used phobic participants, and confronted them
  with the objects of their phobias
• Tulving (1991) pointed out the two methods (lab
  and field) are intended to be complimentary to
  each other, each one supplying some aspect that
  the other lacks

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Laboratory Studies of Detail Recall II

• Loftus and Burns (1982)
• Showed a film of a robbery, in the violent
  version, a young boy was shot directly in the
  face
• Participants who saw the violent version of the
  film were significantly worse at remembering the
  number on the boys shirt (number seventeen)
• Examination of participants recall on other
  details show that they were as good as control
  participants. In some cases they were even better
  than the control participants.
• Christianson Loftus (1987)
• Showed participants the same two films and tested
  their recall 6 months later
• Participants who saw the violent version were
  better able to remember the gist of the event

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Laboratory Studies of Detail Recall III

• Christianson and Nilsson (1984)
• Showed participants a series of slide-pairs of
  faces and descriptive details (e.g. profession,
  hobbies etc.)
• For half of the participants, the middle phase of
  this series showed hideously disfigured faces
• Participants who saw the disfigured faces
  recalled fewer descriptive details than
  participants who saw only neutral faces
• Participants had to recall details that were not
  connected directly to the faces they displayed,
  but instead were the same details as shown for
  the neutral slides

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Theories of Memory and Arousal

• Yerkes and Dodson (1908) proposed an inverted-U
  relationship between arousal and performance. As
  arousal increases so too does level of
  performance until it reaches an optimal level,
  after that further increases in arousal will
  result in decreases in performance

Stress level optimal memory is improved
Stress is too high, memory is impaired
Stress is too low, memory is impaired
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The Yerkes-Dodson Law

• Deffenbacher (1980) reviewed 21 studies of
  eyewitness memory and concluded that most of them
  followed the Yerkes-Dodson relationship, with
  high stress causing memory deficits
• Neiss (1988) criticised the concept of arousal as
  one process, and instead distinguished between at
  least three separate systems
• Electrocortical arousal
• Arousal of the autonomic nervous system
• Behavioural responses
• It is hard to falsify any results that do not
  seem to conform to the inverted-U can be
  explained by either too much too little arousal.

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The EasterBrook Hypothesis

• Easterbrook (1959) an increase of drive to an
  organism is associated with a reduction in the
  range of cues used by that organism
• As stress increases an individuals ability to
  attend to everything in the situation decreases
• In a stressful situation the number of visual
  cues that can be used decreases and only the most
  salient are taken in
• Recall improvement for central details is seen as
  a product of attentional focusing, due to
  increased stress levels
• The Yerkes-Dodson Law predicts either overall
  improvements or impairments. The Easterbrook
  hypothesis allows for improvement in some areas
  and not others

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Support for the EasterBrook Hypothesis

• Yiend Matthews (2001)
• Participants were split into high and low anxiety
  groups, and shown threatening and non-threatening
  pictures
• Highly anxiety participants took significantly
  longer to disengage from threatening pictures
  than low anxiety participants
• Wessel and Merckelbach (1998)
• Compared detail recall for spider phobics versus
  low-fear controls. Participants studied bulletin
  boards containing various central details about
  spiders, and peripheral details of babies, and
  pens
• Spider phobics showed central improvement and
  peripheral deficit compared to controls

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Issues with the EasterBrook Hypothesis

• Although the Easterbrook hypothesis can account
  for many of the findings in stress and memory
  literature there are still some issues to
  consider
• Does stress cause an improvement in central
  recall, a impairment of peripheral recall or
  both?
• Wessel, van der Kooy, and Merckelbach
  (2000)showed participants a series of slides
  differing on one critical slide (either neutral
  or stressful). They also presented participants
  with extensive self-relevant instructions
• The expected pattern of results was observed in
  free-recall tests. Participants in the stressful
  condition did not show the expected recall
  patterns in cued recall tests.
• Concluded that improved central, and impaired
  peripheral, recall was not as stable as
  previously thought and can be affected by the
  experimental technique used

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Issues with the EasterBrook Hypothesis II

• What is meant by central and peripheral
  details? Does it relate to spatial positioning or
  relevance to the gist of the whole slide? How
  tied to the visual stimulus is the effect?
• Burke, Heuer Reisberg (1992) split the
  classification of peripheral detail into
  plot-irrelevant detail that was either
  centrally or peripherally placed on the slide
• Participants in the stressful condition showed
  improved recall for centrally placed
  plot-irrelevant detail, with impairment in memory
  for peripherally placed plot-irrelevant detail
• Laney et al. (2004) used thematically induced
  arousal (using narration rather than picture
  content). They found that in the stressful
  condition memory was improved in all areas

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References and Further Reading

• The reading for this topic is from review
  journal articles. Both are available through the
  Library online catalogue and Leicester e-link
• Christianson, S.A. (1992) Emotional Stress and
  Eyewitness Memory A Critical review.
  Psychological Bulletin 112 (2) 284-309
• Deffenbacher, K.A., Bornstein, B.H., Penrod,
  S.D., et al. (2004) A meta-analytic review of the
  effects of high stress on eyewitness memory. Law
  and Human Behaviour 28 (6) 687-706