Transcript Learning

Implicit Learning II
Dr Magda Osman
Room 2.25
Office hours Mondays & Tuesday
The holy grails of compelling evidence:
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Patient studies – individuals with
neurological impairments
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Double dissociations
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– Patient 1 shows implicit learning
- Patient 2 shows explicit learning
Neuro-imaging studies – different brain functions
associated with different neurological activity
Clinical Studies
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Anaesthesia
Amnesia
Parkinson’s Disease
Prosopagnosia
Blindsight
Split brain
Under Anaesthesia
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Kihlstrom , Schacter, Cork, Hurt, & Behr, (1990) – showed that
when presented with lists of words during surgery, later tests of
memory show above chance accuracy on indirect tests of knowledge

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Failure to replicate (Cork, Kihlstrom, & Schacter, 1992; Jelicic, Asbury,
Millar, & Bonke, 1993)
Hughes, Sanders, Dunne, Tarpey, & Vickers, (1994) –played a “stop
smoking tape” or a “control” tape to people in surgery, I month
later, those with the stop smoking tape reported reduced smoking
behaviour
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Failure to replicate (Myles, Hendrata, Layher, Williams, Hall, Moloney, &
Powell, 1996)
Amnesia
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Knowlton, Ramus, & Squire (1992), Knowlton & Squire (1994, 1996)
reported that amnesiacs can perform as well as normals in judging the
grammaticality of new strings generated from an artificial grammar,
while being very poor at recognizing the training strings.
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Inconsistency (Knowlton, et al, 1992; Knowlton & Squire, 1996)
Knopman (1991), Nissen and Bullemer (1987), Reber & Squire (1998)
showed that also Amnesiacs/ Korsakoff patients could speed up on an
SRT task but cannot verbally report the sequence or, indeed, report
awareness of the existence of a sequence.
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Failure to replicate (Curran, 1997; Shanks, Channon, Wilkinson, &
Curran, 2005)
Parkinson’s disease
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Degenerative disorder – impaired speech and motor behaviour –
deficit to the basal ganglia (reward system), memory loss

(Ferraro, Balota, & Connor, 1993; Jackson et al, 1995;
Westwater et al, 1998) Show deficits in implicit learning (SRT).
Even when the task is presented in verbal form, still leads to
poor or no learning.
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Failure to replicate – show implicit learning in PD patients (Smith,
Siegert, McDowall, & Abernethy, 2001)
Problematic demonstration of implicit– test of awareness, “if you think
there is a sequence say what it is”
Prosopagnosia
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Deficit in processing faces; acknowledge that a face is
there, but cannot recognize that it is a face, let alone
recognizing a familiar face
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(De Haan, Young, & Newcombe, 1991; Jones, & Tranel,
2001) – (case studies) – Failed to explicitly identify
familiar faces after being presented a whole series during
a learning session, but were able to do so implicitly, in
one case, this was indicated through galvanic skin
responses.
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Failure to replicate De Haan & Campbell (1991)
Double dissociation
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Parkinson’s disease patients show impaired
learning on a complex category learning
task, despite maintaining good explicit
memory about task features (Knowlton,
Mangels & Squire, 1996).
In contrast, amnesic patients appear to
show normal implicit learning on the same
complex category learning task, but poor
explicit memory of the task (Knowlton et
al., 1996; Reber, Knowlton & Squire,
1996).
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Implicit
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Explicit
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Implicit
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Explicit
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But….also…
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Parkinson’s disease patients after extensive
training, over 3 days, their performance is
close to those performing normally
(Shohamy, Myers, Onlaor, & Gluck, 2004)
In addition, amnesic patients show
equivalent learning to normals on the same
complex category learning task, and good
explicit memory of the task (Speekenbrink,
Channon, Shanks, 2007).
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Explicit
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Implicit
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Implicit
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Explicit
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Visual system & Blindsight
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Reception of a stimulus in the visual system (Lamme, 2003)
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40 ms: V1 activation
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80 ms: most visual areas activated
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120 ms: visual activation can be found in all cortical areas, including motor
cortex (feedforward activation)
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Later: recurrent activation among neurons (horizontal, feedforward, feedback)
Blindsight (Weiskrantz)
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the ability to respond appropriately to visual stimuli in the absence of
conscious vision in patients with damage to the primary visual cortex
Blindsight and the Dorsal Stream
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Patients with lesions to primary visual cortex
occasionally retain some visual abilities:
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better than chance performance on forced-choice
discrimination tasks
spatial navigation and coordination (i.e. avoid
obstacles, interact with environment)
Thought to be because of other “backdoor” pathways that
send signals to the Dorsal Stream, A.K.A the “Where and
How Pathway”
Blindsight and the Dorsal Stream
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The Dorsal Stream is thought to mediate much
spatial processing and interaction with the
environment
“WHERE”
“WHAT”
Blindsight and the Dorsal Stream
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The Dorsal Stream is thought to mediate much
spatial processing and interaction with the
environment
But the neural activity in these structures does not (is
not alone sufficient to) enter into consciousness
The Hard Problem Returns
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MYSTERY: what is special about neural
activity that leads to awareness ?
NOBODY KNOWS !
Split-Brain Syndrome
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Some cases of severe epilepsy are treated by
severing the corpus callosum that connects
the two hemispheres of the brain.
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The corpus callosum allows information to be
exchanged between hemispheres.
Split Brain
Split Brain
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With the exception of smell, each
hemisphere receives sensory information
and controls movement on the opposite
side of the body (contralateral).
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But, because of lateralization of some
mental processes split-brain surgery can
lead to disorders in consciousness.
Split Brain
Patient fixates on
the mid line.
In panel on the
right the visual
information and
the language
centres cohere
In panel on the
left the visual
information and
the language
centres are
incoherent
General questions raised
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Is there really evidence for implicit
processes?
Can the findings be explained by
procedural artefacts?
Implicit learning
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Some research suggested that performance on many implicit
learning tasks is unimpaired in patients with neurological
damage:
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E.g. amnesic individuals lack declarative knowledge of task features, but
performance equivalent to normals on indirect tests of knowledge
This is taken as evidence for a multiple systems view of
learning, in which one is procedural (implicit) and is dissociated
from declarative (explicit) learning system.
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The implicit learning system is designed to monitor the environment for
reliable relationships between events (covariations)
Is an evolutionary old system – which is also why it may be immune to
neurological insult
No Implicit learning
Problems with studies showing implicit learning:
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Many of the published studies showing implicit learning in
neurological patients, shown a numerical advantage for
controls
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Low statistical power
The explicit measures are not exhaustive
Heavily biased
Relying on null effects
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No Implicit learning
Theoretical accounts: (exemplar theories - Nosofsky & Zaki, 1998)
(SRN – Kinder & Shanks, 2001, 2003)
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Often- neurological patients can show learning that is equivalent to normals,
given the right learning conditions, and using detailed and fine grained
analyses.
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Neurological damage often leads to slower learning rates, but the learning
mechanism appears to be the same for patients and normals
Problems with dualist argument?
Wanting their cake and eating it:
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Assume dissociable learning mechanisms, but claim that they can
interact,
Assume that learning can be implicit and automatic, but assume they
are different things, - but supported by the same implicit learning
system
Neural localization of different reasoning mechanisms is not
tantamount to evidence for qualitatively distinct reasoning systems
(Sherry & Schacter, 1987)

Why?
Problems with single system argument?
Wanting their cake and eating it:
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There could be a continuum between implicit and explicit
learning processes (Cleermans & Jiménez, 2002) – but this is
very difficult to empirically test.
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Theorists (e.g. Shanks & St John, 1994) that deny that there
are processes that are unconscious are failing to accommodate
much empirical research.
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The arguments against measures used to examine implicit
processes, make it an impossible task to demonstrate
unconscious learning.
Summary I
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Phenomenal, perceptual awareness
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Recurrent interactions in early visual areas: binding, segregation,
perceptual organization.
Mammals, birds, reptiles?
Access awareness (introspective)
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Recurrent connections to higher centers – executive, memory:
putting stimulation in context of current goals. Only then it can
be reported.
Humans only (language?)
Summary II
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Attention without awareness: selection of stimuli which did
not reach perceptual awareness
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Awareness without attention: stimuli may enter perceptual
awareness but they do not reach access awareness
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Only stimuli that reach access (introspective) awareness can
be reported.
The last stage seems to be related to consciousness:
• Recurrent activation among neurons appears to be the key
aspect of the brain that corresponds to consciousness

Recently
• Transcranial Magnetic Stimulation (disrupts activity in a particular brain
region) – stimulus presented over the threshold may remain invisible;
All stimuli above a threshold evoke
feedforward activation, but for a
conscious experience recurrent
activation is necessary.
Larger receptive fields as activation
spreads -> competition (selection)
quality of activity – not a localized
centre is the key to consciousness
Critically evaluate clinical evidence
that suggests there is a dissociation
between implicit and explicit learning
processes.