ON THE RELATIONSHIP BETWEEN MOTOR AND PERCEPTUAL BEHAVIOR A SDT FRAMEWORK Andrei Gorea with Pedro Ca

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ON THE RELATIONSHIP BETWEEN MOTOR AND PERCEPTUAL
BEHAVIOR A SDT FRAMEWORK Andrei
GoreawithPedro Cardoso-LeiteFlorian
WaszakPascal MamassianLaboratoire de
Psychologie de la PerceptionCNRS René
Descartes University71 Ave Edouard Vaillant,
92774 Boulogne-Billancourt, France
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SYNOPSYS

• Background elements
• RT Perceptual States with masked and not-masked
  stimuli
• 1 A one-path two-decisions model
• RT Temporal Order Judgments
• 1 One-path two-decisions model again
• General conclusions

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PART I SOME BACKGROUND
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Most frequently used experimental paradigms
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B. The 2 pathways view
Decision rule not specified
Action with or without perceptual awareness
?
dorsal
Sensory Input
ventral
Verbal report aware / not aware
Decision rule (implicit)
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Most frequently used experimental paradigms
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None of the experimental paradigms used to
explore the sensorimotor dissociation allowed a
trial-by-trial analysis of the relationship
between the motor behavior the state of the
perceptual system (Hits, FA, Misses, CR).
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PART II RESPONSE TIME PERCEPTUAL STATE
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Stimuli Paradigm (one trial)
Waszak Gorea (2004).
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Of the 4 perceptual response categories, Hits
Misses are of particular interest They tell us
about the motor behavior when the Obs. says he
senses and does not sense the test stimulus (S1),
hence establishing the relationship between
perceptual and motor behavior. RT for FA
are not reliable indices as they have an unknown
temporal origin RT for CR are simply used as
reference for the relevant RT.
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4 Sjs S1 13 ms SOA variable S2 36 ms 300 trials
/ d / Obs

• The motor system appears to react if and only if
• the stimulus is present
• and
• the observer is aware of it (i.e. only for
  Hits).
• The difference between RTs for Hits Misses
  points against a full sensori-motor dissociation.

Waszak Gorea (2004).
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AG
SD
pS1
FW
.2
.5
.8
Waszak Gorea (2004).
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Weve thus replaced the standard 2-pathways view
B. The 2 pathways view
Decision rule not specified
Action with or without perceptual awareness
?
dorsal
Sensory Input
ventral
Verbal report aware / not aware
Decision rule (implicit)
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Where does the discrepancy come from? (Aside from
potential methodological problems in previous
studies)
Common denominator Most of the previous (whether
simple or choice RT) studies used 100 contrast
targets whose invisibility was ensured by
strong backward masking.
In contrast, our targets (S1) yielded maximum
contrasts of about 20. To allow for higher
target contrasts while keeping sensitivity
constant, shorter SOA-s (48 ms instead of an
average of 162 ms) were used in a second series
of experiments these entailed S1 contrasts
around 30.
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Waszak Gorea (2004).
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The temptation was strong to conclude (Gorea
Waszak, 2004)
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17 Obs 300 trials / d / Obs
Perceptual MISSES
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13
NOT Masked
13
Masked
NOT Masked
27
Masked
0.5
1
1.5
2
2.5
d'
Waszak Gorea, new experiments.
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However, the data are more intricate than that
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Waszak Gorea, new experiments.
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Waszak Gorea, new experiments.
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And a simpler, one pathway SDT model can account
for them. Instead of
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A conceptual model
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Masked (metacontrast)
NOT Masked
S2 mask
S1 prime
S2
S2
S2
t
S1
S1
SOA
SOA
d
Perceptual Misses
Perceptual Misses
Motor threshold
d
RTd2
RTd2
RTMask
RTMask
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Masked (metacontrast)
NOT Masked
S2 mask
S1 prime
S2
S2
S2
S1
t
S1
7
SOA
SOA
d
6
5
Perceptual Misses
4
Perceptual Misses
3
RESPONSE (Noise units)
Motor threshold
d
2
1
0
240
340
40
140
-60
-1
TIME (ms)
RTd4
RTd4
RTMask
RTMask
-2
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Model Fits
Motor Threshold ?.8s
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TAKE-HOME MESSAGES (Part II)

• A one-pathway model with two distinct activation
  levels accounts for the observed perceptual-motor
  relationship under both masking and non-masking
  experimental conditions.
• There is a fixed motor threshold (? 0.8s) ? to be
  contrasted with a variable perceptual criterion).
• The motor threshold is measured in noise (s)
  units as referred to the absolute perceptual
  detection threshold (i.e. in ref. to the
  internal noise).
• RT for unconscious stimuli (i.e. Misses)
  depends on the reference (noise) level at which
  the perceptual task is performed
• as this reference level exceeds the motor
  threshold, the internal response associated with
  perceptual Misses also exceeds it and
  progressively contributes to shortening the RT.

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PART III RESPONSE TIME TEMPORAL ORDER
JUDGMENTS
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Temporal Order Judgments RT IFF RT is
strictly dependent on the sensory signal (as it
determines the TOJ), then the slope and the PSS
of the TOJ ?-function should be direct indicators
of the variance of the RT distributions and of
their mean difference, respectively this is a
one-pathway sensorimotor model.
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Stimuli Paradigm (one trial)

• In contrast with previous studies
• TOJ and RT were measured in the same trial
• It was hence possible to assess RTs for correct
  incorrect TOJs.

a
b
c
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Correct / Incorrect
m-RT
Incorrect
Identical
Correct
S1 1st
Different
S2 1st
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a
b
R
R
CHigh
CLow
Mq
PC
PSS
PSS
PT1
PT2
RT
RT1
RT2
Mq lt PC
Mq PC
Mq gt PC
DRT
t
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TAKE-HOME MESSAGES (Part III)

• For 2 out of 4 Obs, RT to single stimuli also
  predict their TOJ behavior (PSS and slopes of the
  TOJ Y-fct.) their behavior is hence compatible
  with a one pathway model (no sensorimotor
  dissociation).
• For these 2 Obs, the relationship between
  RT-differences and PSS also suggests the
  existence of a motor threshold distinct from and
  higher than the perceptual criterion.
• The behavior of the remaining 2 Obs does not
  follow any coherent pattern it is likely that it
  was perturbed by perceptual response strategy
  factors, possibly under the influence of
  transient Troxler masking (Kanai Kamitani,
  2003).
• Such factors may account for the various
  inconsistencies in the RT-TOJ literature.

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GENERAL CONCLUSIONS

• The relationship between simple Response Times
  and perceptual states (Hits, FA, etc. and
  Temporal Order Judgments) can be accounted for by
  a single (one-path) system where two distinct
  decisions are made on the same incoming
  information.
• The decision to act is based on a hard-wired
  threshold worth about 1s of the internal noise
  the perceptual criterion is context dependent (in
  line with SDT).
• TOJ data not complying with this model may
  reflect variable perceptual response strategies.

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THANK YOU
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Intermediate conclusion ONE pathway, TWO outputs
MOTOR RESPONSE
X
dorsal
Stimulus present Awareness of it
ventral
PERCEPTION
Gorea Waszak, 2004
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Rank Correlations between RT and S1-, S2-onsets
as a fct. of RT Hits only

• The faster the RT, the higher the likelihood that
  it was triggered by S1
• The slower the RT, the higher the likelihood that
  it was triggered by S2
• The correlations for Misses are null (as
  expected).

Additional data from Waszak Gorea (2004).
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Spearman Correlations between RT and S1, S2
onsets as a fct. of RT Hits only

• The faster the RT, the higher the likelihood that
  it was triggered by S1
• Conversely, the slower the RT, the higher the
  likelihood that it was triggered by S2.

Data from Waszak Gorea (2004). Visual Cognition.
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If motor threshold and perceptual criteria differ
significantly, the same should be true for the
temporal dispersion of R at each of these two
levels (see Carpenter).
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If the motor threshold and perceptual criteria
differ significantly, the same should be true for
the temporal dispersion of the internal response,
R, at each of these two levels (see Carpenter et
al.).
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Reddi Carpenter (2000). Nature Neurosci., 3,
827-830.
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What does the Obs. Compare?
vs.
A
OR
vs.
B
OR
Becker Anstis (2004) Vision Research 44,
25372543 No backward masking with opposite
polarity Test-Mask
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What do the Obs. compare?
OR
OR
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Temporal Order Judgments RT IFF RT is
strictly dependent on the sensory signal (as it
determines the TOJ), then the slope of the TOJ
?-function should be a direct indicator of the
variance of the RT distribution (see Adams
Mamassian, 2004).

• In contrast with previous studies
• TOJ and RT were measured in the same trial
• It was hence possible to assess RTs for correct
  incorrect TOJs.

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?7
NOT Masked
22.5
Masked (metacontrast)
criterion modulation
S2
S2
S2 Mask/Primed (p 1)
S1
S1 Target/Prime (p .2, .5, .8)
T0 Start Clock
Hits FA Misses CR
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20
100-200
Correlation S2-RT
Correlation S1-RT
T I M E
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Masked (metacontrast)
NOT Masked
S2 mask
S1 prime
S2
S2
S2
t
S1
S1
SOA
SOA
d
Perceptual Misses
Perceptual Misses
Motor threshold
d
RTd2
RTd2
RTMask
RTMask
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• Of main interest for further research
• The direct assessment of the motor threshold
• Still searching for the critical paradigm.
• Test the reference noise level idea in
  metacontrast and revise metacontrast models
  accordingly
• The empirical test could consist in manipulating
  the external noise under masked and unmasked
  conditions.

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