Transcript Document

We explored the impact of duration of the
primer and complexity of the decision in a
"Same"-"Different" task. The signature of
priming was found. Using holistic or discrete
objects changed the results, as predicted.
See "A few pilots to drive this research".
What is priming then?
Priming may have a highly adaptive value:
parallel systems operating in real time must
be able to anticipate the processes to come
next in order to reduce the number of
possibilities. Thus, internal priming is the
most natural outcome of PDP.
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"Same"
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Complexity
4
• The probe complexity C (string length) was 1 to 4;
• Duration of the first slide not controlled by Bamber;
• If different, the probe had from 1 to C differences.
Arguin & Bub, 1995
Primer
N
*
D vary
100 ms
*
100 ms
*
N
Primed
Neutral
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"Letter"
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150 100
Duration
• The complexity C of the probe is always 1
• The duration of the prime D is varied (50..200 ms).
C) Number of masks in a
cued detection task
Shiu & Pashler, 1997
50 ms
*
50 ms
*
50
One
50
Four
Eight
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30
4
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50 ms
20
"4"
S, BG, LFT, BFGK, etc.
• Task:
"Same"-"Different" task a la Bamber (1969)
Decidor
Response
Size k
Pilot 1: Duration of primer and complexity of
decision with holistic stimuli.
Duration has a concave effect
(reproducing Arguin and Bub).
This suggests that the number of
reminiscent activations (r) is the
only factor changing with duration.
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B) The "letter"-"non-letter" priming task
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Detectors
S, BG, LFT, BFGK, etc.
Valid Neutral Invalid
Cue validity
• With no primer (neutral),
there is no effect of the
duration D.
• With a primer, responses
are concave and faster
than neutral conditions.
• The fact that the results
and the experimental
procedures in A & B are
identical suggests that the
same mechanisms are
active.
• For a given cue validity,
the decrease in accuracy
is larger between 4 and 8
masks than between 1
and 4.
• Strength theories cannot
accommodate these
results, including
weighted neural network.
• Complexity C and duration D are held constant at 1 and 50 ms resp.
• The number of masked locations following the probe is varied (1, 4 or 8).
D) A feature detection task
Cousineau & Shiffrin, in prep.
33 ms
33 ms
Number of features
33 ms
""
• Detecting well-learned features/configurations is easier;
• There is no primer (Ss were trained in a different task),
suggesting that preactivation can be internalized.
• The small decrement in
accuracy when increasing
the number of features
(complexity) from 1 to 2
compared to the large
decrement between 3 and
4 is against predictions of
limited-capacity models.
• Clearer, stronger and longer signals activate a larger number of
detectors
r, the number of active channels, is a linear function of the "clarity" of the signal
• More difficult responses, resulting from more complex stimuli,
requires higher thresholds from the deciders
k, the size of the accumulator, is a linear function of the complexity of the signal
• All the channels are racing to fill a decider and all the deciders
are racing to make a response
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Duration of the primer
on RT to say "Same"
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rt
Probe 
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100 ms
*
ASF
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100
50
d
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Complexity of holistic stimuli has a
linear effect. This suggests that
the subjects are increasing their
threshold with increased
complexity of the object (as well
as receiving less evidences r).
Complexity of decision
on RT to say "Same"
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340
rt
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*
Holistic:
Separable:
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{this is a parallel race model, Cousineau, Goodman and Shiffrin, in press}
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1
2
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4
c
To say different, there is no interaction of complexity of
the objects with the number of differences between the
primer and the probe. This suggest a constant
threshold to say "Different".
Predicting priming
1. Concave:
r alone changes
2. Straight:
3. Convex:
r and k changes
k alone changes
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rt
Preliminary tests
100 ms
"Different"
• Stimuli:
rt
Stronger, clearer and longer signals
generate reminiscent activation in a larger
number of channels. This assumes that
the channels are highly redundant.
However, more complex decision can
result in a more stringent threshold. See
the section "Predicting priming".
free
460
15 hours, including 5 of practice.
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diff
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2
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3
4
Number of differences
on RT to say "Different"
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340
320
1
2
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c
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2
3
4
diff
Pilot 2: Complex decision with separable stimuli.
1. Altering the "clarity" of the primer (such as its duration) will leave
a larger number of reminiscent channels which are easier to
reactivate. Reducing r alone predicts a concave curve.
2. Increasing the complexity of the input will necessitate a larger k.
However, the activated channels will be spread out and more
likely to decay. Reducing r and increasing k predicts a straight
line.
3. Curiously, if we could change k while keeping the number of
activated channels constant, we would inverse the curve.
Increasing k alone predicts a convex curve.
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Complexity of decision
375 on RT to say "Same"
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350
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rt
What factors modulate priming?
ASF
*
"Same"
• Well-trained subjects:
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c
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rt
Priming might be some reminiscent
activation left in the system after the
presentation of a primer. Assuming a
thresholded network of connections,
predictions can be derived. See the
section "A model to model redundancy".
Bamber, 1969
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• Since weighted connections cannot accommodate the various
results, we set all connection weights to 1.
• We explored redundancy. A single piece of evidence can travel
through a large number of redundant channels.
"Same"
What is the cause of priming?
A) The "Same"-"Different" task
• "Different" responses
suggest a serial selfterminating search for the
first difference BUT!
• "Same" responses are
concave and faster than
"Different", rejecting any
serial model
(Sternberg,1998).
A few pilots to drive this research
"Same"
Priming is a phenomenon in which
facilitation occurs in low-level tasks.
Mechanisms of priming may also play a
central role in other phenomenon. See
"The signature of priming" section.
Priming seems to have a typical signature, seen in the data as a
concave curve which is a function of complexity (A & D below),
duration (B) and number of cues (C). This pattern of results is
seen in simple tasks having similar experimental procedures.
A model to model redundancy
"Different"
What is priming?
The signature of priming
"Same"
Plan (p)
"Different"

Denis Cousineau, Sébastien Hélie, Christine Lefebvre, Université de Montréal
Reaction times
Plan p  q
Reaction times

P(errors)
Plan p
To join the authors:
Denis.Cousineau@
umontreal.ca

"Same"-"Different", cue validity and detection task fitted by a parallel race model:
The ubiquitous presence of priming
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diff
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c
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Here, complexity has a concave
effect (reproducing Bamber). This
suggests that the threshold
operates on individual letter and is
not affected by the length of the
string.
To reject a whole string, there is
an interaction of complexity with
the number of differing letters. The
threshold in this case seems to be
modified by the complexity of the
string to reject.