Implicit Memory

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Implicit Memory
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Claparede described a amnesic patient. She could
add and spell but did not recognize her doctors
or nurses. When Claparede would meet his
patients in the morning he would shake their
hands. One day he hid a small pin in his hand.
The amnesic patient got a small prick that
morning. The next morning she didnt want to
shake his hand. She said, Sometimes people hide
things in their hands.
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Dissociation

• There seems to be a difference in long term
  memory
• We may know how to ride a bike but it is very
  difficult to explain how you do so
• Thus we distinguish between explicit memory
  (knowing information about a bike) and implicit
  memory (knowing the physical process of riding
  the bike)
• Implicit memory often characterizes acquisition
  of motor skills, conditioning, and habituation

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The Study of Implicit Memory

• Topics of study
• Childrens Language Acquisition
• Learning Artificial Grammar
• Redundant Sequence Learning
• Priming
• Skill Acquisition

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Learning Grammar

• Example of children learning language
• There are explicit rules to which certain
  sequences of grammatical forms are permissible
• Children are able to use their native grammar
  very well before being taught the rules
• Children are unable to describe the underlying
  grammatical rules
• Implicit learning?

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Learning Artificial Grammar

• Reber (1967) used an Artificial Grammar defined
  by a series of rules about how letters may be
  related to one another
• One group learned sequences of letters generated
  by the grammar and the other group learned random
  letter sequences
• Both groups were shown letter strings, half
  grammatical and half random letters
• Subjects who learned grammatical sequences
  recognized 79 of the new grammatical sequences

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Redundant Sequence Learning

• Bullemer (1987) used the idea of repeated
  sequences to test implicit learning
• Subjects performed a button press task that
  corresponded to spatial locations on a computer
  screen
• One group performed under random conditions and
  the other under redundant conditions
• The redundant group speeded up in their RxN times
• Implicit Learning?

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Redundant Sequence Learning

• Though some subjects performed faster on the test
  some could describe the pattern explicitly and
  some could not
• How sure are we that the second class of people
  did not really have explicit access to the
  knowledge?
• During testing of the unaware group the
  experimenter stopped and asked for a prediction
  of next location. Performed at chance

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Lets Believe in Implicit Learning

• If we believe in Implicit Learning then it seems
  that people are unconsciously acquiring rules
  that they can use but not articulate
• Are rules really being learned?
• When an individual learns an artificial grammar
  or improves performance after repeated
  presentations, do they acquire abstract rules
  implicitly or do they memorize specific exemplars
  that are accessible to explicit memory?

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Implicit Evidence (Transfer)

• Reber (1969) - Two phases of grammar learning.
  Study phase learners acquired a string
  discrimination based on an artificial grammar.
  Testing phase one aspect of the learning task
  was changed (rules or letters)
• Both changes caused problems, but there was a
  larger problem for the rules condition
• Thus learners acquired and transferred implicit
  knowledge of rules

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Explicit Evidence

• Individual Exemplars - accepts the transfer
  findings, accounts for them by assuming that
  learners compare test strings in terms of their
  structural similarity. This is kind of like rule
  learning, however this process occurs during
  testing, not during study (explicit)

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The Non-Believers

• Subjects may know something about the task they
  are acquiring, however, whether it is enough to
  give an explicit explanation is a different
  matter
• Though explicit information is available, it may
  lack the merit for description

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The Criteria

• The subject must not be aware of the association
  at time of learning
• Information Criterion - must show that the
  information sought in the awareness test is
  really responsible for performance change
• Sensitivity Criterion - must have a measure of
  unconscious learning that has the appropriate
  sensitivity to the learning

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How Do We Address These Issues?

• Example
• Testing awareness during learning is rather
  difficult
• Therefore test people under anesthesia
• Theoretically awareness is manipulated by the
  experimenter
• Does some to be some evidence for learning under
  these conditions, but it is not conclusive

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Priming

• Considered strong evidence for Implicit Learning
• Refers to the influence a stimulus has on
  subsequent performance (positive or negative)
• Can be on the visual, spatial, phonological, or
  semantic level
• A number of paradigms have been developed
• Perceptual Identification, Word Stem Completion,
  Word Fragment Completion, Degraded Word Naming,
  Anagram Solving,

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Priming Example

• Word Completion Task
• Subjects inspect a list of words without being
  asked to memorize them
• During testing, people receive word stems such as
  riv__ or e_e_an_
• Lexical Decision Task
• Identify Words and Non-words (i.e. grobse...)
• RxN time for repeated Non-words will decrease if
  it has been repeated

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Priming Characteristics

• Roediger (1993) Priming effects tend to be
  modality-specific
• Sensitive to physical features, with some
  exceptions (i.e. visual modality)
• Does not seem to be sensitive to issues relating
  to Levels of Processing
• The implicit memory aspect of priming is much
  more durable over time compared to explicit
  memory
• Relatively Insensitive to drug manipulations

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Priming and Amnesiacs

• Perhaps the most experiment is testing amnesic
  patents with priming paradigms
• Example - Graf (1984) required amnesic and
  control subjects to learn a word list. They were
  then given a stem-completion task and a recall
  task. There was a clear difference between the
  groups on the recall task but no difference on
  the stem-completion task

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Skill Acquisition and Amnesiacs

• H. M. - was able to acquire motor skills with
  relative ease
• Milner (1962) showed that H. M. improved daily on
  a mirror tracking task
• Nissen (1987) showed that amnesiacs performed the
  same as normals on redundant learning tasks
• Knowlton (1992) amnesiacs could learn artificial
  grammars

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Conditioning and Amnesiacs

• Amnesic patients can be conditioned just as a
  normal subject
• Amnesic patients could be conditioned for
  eye-blinking. However, they were unable to
  describe the function of the air nozzle