Cognitive Library Module, Topic 2 The Mechanisms of Boundary Extension

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Cognitive Library Module, Topic 2The Mechanisms
of Boundary Extension

• Dr. Sophia King

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Research into Scene Memory

• Visual memory is our record of the world around
  us, but how accurate is this record? Sometimes,
  memory distortions can be seen in the way in
  which we view artificial views of the world,
  i.e. 2-D scenes.
• Pezdek et al. (1988) focused on the memory of
  details within the scenes. Found that memory for
  details was often confused by the general gist of
  the particular scene.
• Henderson et al. (2004) looked at how people move
  their eyes around scenes. Eye movements as an
  indicator of attention and object salience.

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Memory for spatial positioning

• The memory distortion that this topic focuses on
  is one of the spatial layout and angle from which
  a scene is viewed by the individual.
• Boundary extension is the tendency to recall
  information that was not shown in the picture but
  that was likely to have existed just outside its
  boundaries (Intraub and Bodamer, 1993, p1387).
• Main objects are remembered as being smaller
• Scene appears as if it was viewed from further
  away
• More background information is included

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Boundary Extension
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The Methodology of Boundary Extension

• The two major ways of testing scene memory for
  boundary extension are
• Drawing Tasks participants reproduce the scene
  they have just viewed in the same sized space.
  The space covered by the major objects is
  compared to the actual scene to measure amounts
  of boundary extension
• Recognition Tasks participants view scenes
  twice. For the second viewing they must judge
  whether or not the scene is the same, appears
  further away, or appears closer up.
• Close-up versus wide-angle views

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Recognition Tests Examples of Stimuli
Wide-angle view
Close-up view
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Research into boundary extension

• BE was first noted by Intraub Richardson in
  1989 as an error in participants drawings.
• Intraub saw only unilateral errors (boundary
  extension not boundary restriction)
• Boundary extension occurred in the majority of
  drawings
• Boundary extension was seen not just in tests of
  drawing but also in recognition tests
• Nyström (1993) compared artistically talented
  participants to participants without artistic
  talent. Although the first groups drawings were
  more aesthetically pleasing, boundary extension
  was still observed

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Research into boundary extension II

• Boundary extension has been shown to have certain
  characteristics that shed light onto the
  underlying mechanisms behind the phenomenon.
• Boundary extension is robust. It can still be
  seen even when participants are given a warning
  and a demonstration
• The largest amounts of extension are seen for
  scenes that are the most closely focused. The
  wider the focus of the scene, the less boundary
  extension is seen
• Extension effects change over time. With delayed
  recall tests (e.g. 48 hours) boundary restriction
  begins to appear in certain cases

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Investigating the mechanisms of boundary extension

• This topic is concerned with the phenomenon of
  boundary extension, and the underlying theories
  used to explain it.
• What boundary extension reveals about our
  memories
• How real-world knowledge is incorporated into our
  memory of the world around us
• How the characteristics of boundary extension are
  explained by Intraubs theory
• How the immediate and delayed findings of
  boundary extension are reconciled

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Core Articles

• Intraub Richardson (1989)
• The first paper to investigate boundary
  extension, focused on spatial positioning rather
  than objects within the scene
• Explains the methodology of investigating
  boundary extension
• Drawing reproduction tasks
• Recognition-judgement tasks
• Considers boundary extension as a product of
  object completion

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Core Articles II

• Intraub, Bender, Mangels, (1992)
• Investigates the underlying causes for boundary
  extension
• Uses immediate and delayed (48 hours) testing
• Suggests a variety of potential explanation for
  the boundary extension findings
• Object completion
• Schema-based models
• Perceptual schema hypothesis
• Memory schema hypothesis
• Considers boundary extension in relation to other
  memory distortions and what it tells us about the
  way in which our memories work

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Core Articles III

• Intraub, Gottesman, Bills, (1998)
• Goes further into the idea of boundary extension
  as the product of a schema
• Investigates what is necessary in a scene to
  produce boundary extension
• Real scene versus line-drawn scenes
• Blank backgrounds versus more complex backgrounds
• Imagination as a trigger for boundary extension

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Core Articles IV

• Gottesman Intraub (2002)
• Continues to investigate the properties of
  boundary extension and how these characteristics
  relate to top-down knowledge about the world
• Uses cut-out objects on blank backgrounds to
  investigate what exactly makes a scene a scene
  (in order for boundary extension to occur)
• Introduces ideas of amodal continuation

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Additional Reading Issues to Consider

• Additional papers on boundary extension are
  included on Blackboard. These extra articles
  raise other issues to consider
• The robustness of boundary extension
• Participant groups of different ages
• Different task demands
• The applicability of boundary extension to other
  stimuli
• Real-world scenes
• Neutral versus emotional stimuli

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Organising your reading study questions

• What evidence is there that boundary extension is
  a real phenomenon and not just an artefact of the
  testing method?
• What are the different theories proposed by
  Intraub and her colleagues that can explain the
  boundary extension effect?
• What factors about viewing scenes are thought to
  be crucial for the formation of boundary
  extension?
• What is the extension-normalisation hypothesis?
  How does it relate to other theories that seek to
  explain boundary extension?