1
2
3
4
diff
1 2 3 4
c 350
375 400 425 450 475
rt
A few pilots to drive this research
• Well-trained subjects:
15 hours, including 5 of practice.
• Stimuli:
Holistic:
Separable:
• Task:
"Same"-"Different" task a la Bamber (1969)
Pilot 1: Duration of primer and
complexity of decision with holistic stimuli.
Pilot 2: Complex decision with separable stimuli.
S, BG, LFT, BFGK, etc.
"Same"-"Different", cue validity and detection task fitted by a parallel race model:
The ubiquitous presence of priming
Denis Cousineau, Sébastien Hélie, Christine Lefebvre, Université de Montréal
What is priming?
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.
What is the cause of priming?
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".
What factors modulate priming?
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".
Preliminary tests
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.
A) The "Same"-"Different" task
ASF
*
*
* ASF
free
100 ms
100 ms
Bamber, 1969
• 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.
Probe "Same"
• "Different"
responses suggest a serial self-
terminating search for the first
difference BUT!
• "Same" responses are concave and faster than
"Different",
rejecting any serial model
(Sternberg,1998).
320 340 360 380 400 420 440 460 480
1 2 3 4
Complexity
Reaction times
"Same"
"Different"
*
To join the authors: Denis.Cousineau@ umontreal.ca
The signature of priming
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
•
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.
•
Clearer, stronger and longer signals activate a larger number of detectors
, 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
, 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
{this is a parallel race model, Cousineau, Goodman and Shiffrin, in press}
Predicting priming
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 alone predicts a concave curve.
2.
Increasing the complexity of the input will necessitate a larger . However, the activated channels will be
spread out and more likely to decay. Reducing and increasing predicts a straight line.
3.
Curiously, if we could change while keeping the number of activated channels constant, we would
inverse the curve. Increasing alone predicts a convex curve.
B) The "letter"-"non-letter"
priming task
N
*
*
* N
D vary 100 ms
100 ms
Primer Arguin & Bub, 1995
• The complexity C of the probe is always
• The duration of the prime D is varied 1 (50..200 ms).
• 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.
345 365 385 405 425 445 465 485 505 525
50 100
150 200
Duration
Reaction times
Primed Neutral
C) Number of masks in a cued detection task
Shiu & Pashler, 1997
20 30 40 50
Valid Neutral Invalid Cue validity
P(errors)
One Four Eight
• 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.
*
* 4
*
50 ms 50 ms
50 ms
D) A feature detection task
33 ms 33 ms
33 ms
Cousineau & Shiffrin, in prep.
Number of features
• Detecting well-learned
features/configurations is easier;
• There is no primer (Ss were trained in a different task), suggesting that
preactivation can be internalized.
• 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). • 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.
Detectors
Decidor
Response Size
1. Concave:
alone changes 2. Straight:
and changes 3. Convex:
alone changes
S, BG, LFT, BFGK, etc.
1
2
3
4
diff
1 2 3 4
c 320
340 360 380 400 420
rt
"D iff er en t" "D iff er en t" "S am e" "S am e"
50 100
150 200
d 320
340 360 380 400 420
rt
Duration of the primer on RT to say "Same"
1 2 3 4
c 275
300 325 350 375 400
rt
Complexity of decision
on RT to say "Same"
1 2 3 4
diff 320
340 360 380 400 420
rt
Number of differences on RT to say "Different"
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.
"S am e"
1 2 3 4
c 300
310 320 330 340 350 360
rt
Complexity of decision on RT to say "Same"
Duration has a concave effect (reproducing
Arguin and Bub). This suggests that the
number of reminiscent
activations () is the only factor changing with
duration.
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 ).
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".
Plan p
Plan p q
Plan (p)
"Letter"
"4"
""
