1. No category

EUROPEAN JOURNAL OF BEHAVIOR ANALYSIS
2007, 8, 177 - 191
NUMBER 2 (WINTER 2007)
177
Different Retention Intervals in Delayed
Matching-to-Sample: Effects of Responding in
Accord with Equivalence
Erik Arntzen1, Tommy Galaen2, and Lars Rune Halvorsen2
Akershus University College1 and Ostfold University College2
The purpose of the current experiment was to replicate and to extend the findings of the study by
Arntzen (2006). We investigated the probability of responding in accord with stimulus equivalence
as a function of increasing and decreasing retention intervals. In the one-to-many training structure
with delayed matching to sample the retention intervals were 0 s, 6 s, and 12 s. Twenty adults served
as participants – ten participants started with 0 s delay and ten participants started with 12 s delay,
and the retention intervals were either increased or decreased. For each condition it was a novel set
of abstract, arbitrary stimuli. Nine of ten participants responded in accord with equivalence for the
participants either when the retention interval increased or decreased. However, all participants met the
symmetry criterion. Reaction time was higher on “equivalence” trials compared to “symmetry” trials,
and the typical pattern of an increase from baseline trials to the first test trials and a decrease during
the test was most pronounced for the “equivalence” trials.
Key words: stimulus equivalence, delayed matching to sample, retention intervals, adults, precurrent behavior, reaction time.
Behavior analysis has identified basic behavioral principles governing both simple and complex human behavior, and has studies secondary
principles derived from more fundamental
behavioral principles (Donahoe & Palmer,
1994). Behavioral terms encourage parsimonious explanations, concurrently omitting circular
reasoning, explanatory fictions and reifications
(Skinner, 1953). Even though categorization
and concept learning historically have been area
for cognitive psychology and not a primary subject matter for experimental analysis of behavior,
research on stimulus equivalence has been important for an understanding of such complex
human behavior (Sidman, 1994). Thus, lately
research on conceptual repertoires and learning
histories which make these repertoires possible
have been discussed (e.g., Critchfield, Galizio,
& Zentall, 2002). For example, verbally competent humans
“....often react to words and other
symbols as if they are the things or
events they refer to. ....This treatment of
linguistic forms as equivalent to their referents permits us to listen and read with
comprehension, to work out problems
in their absence, to instruct others by
means of speech or text, to plan ahead,
to store information for use in the future,
and to think abstractly - all of these by
means of words that are spoken, written,
or thought in the absence of the things
and events they refer to” (Sidman, 1994,
p.3).
Thanks to Ruth Anne Rehfeldt and John Donahoe for
valuable comments for her comments on an earlier version of
the manuscript. Correspondence concerning this manuscript
should be addressed to Erik Arntzen, Akershus University College,
PO Box 423, 2001 Lillestrom, Norway. E-mail: erik.arntzen@
equivalence.net
Concepts have been defined as generaliza177
178
Erik Arntzen, Tommy Galaen, and Lars Rune Halvorsen
tion within categories or classes of stimuli, and
discrimination among classes of stimuli (Keller
& Schoenfeld, 1950). Hence, stimulus class
formation warrants applicable experimental research to account for several complex behaviors.
Although complex behaviors may not be readily
observable, some lend themselves to experimental behavior analysis (see Palmer, 2003 for
a discussion on interpretation). Furthermore,
Donahoe (2004) has stated that “Interpretation
may appeal to unobserved events (e.g., operants)
as long as three requirements are met (Skinner,
1957, 1984): (a) The unobserved operant must
be of a kind that has been subjected to prior
experimental analysis. (b) The antecedents that
prevail when the unobserved operant is invoked
must include the critical antecedents identified
when it was subjected to experimental analysis.
(c) The prevailing conditions must contain antecedents known to be present in the history of
the individual when the behavior was reinforced
or, minimally, that such antecedents were very
likely a part of the history of the individual”
(p. 85).
Sidman (1994) has for example argued that
through stimulus equivalence research more
complex behavior may emerge and be explained. Emergent equivalence relations refer to
demonstrations of relations among stimuli that
have not been explicitly trained. An equivalence
class is defined by mutually interchangeable
stimuli that hold all possible emergent relations
between them. It requires at least three stimuli
and two classes to occasion all logical relations
that account for equivalence class formation.
Mathematical set theory provides the descriptive system to classify logical stimulus relations
as demonstrations of reflexivity, symmetry, and
transitivity (Sidman, 2000).
Fields and Verhave (1987) proposed that the
different structural relations of an equivalence
class could best described by four parameters:
(1) number of stimuli per class, (2) training
structures, (3) number of nodes, (4) and distribution of single stimuli. There are three different
training structures, i.e., one-to-many (OTM) or
sample-as-node, many-to-one (MTO) or comparison-as-node, and linear series (LS). In the
current study, we have used an OTM training
structure, because the OTM training structure
have given the highest yields of responding in
accord with equivalence in our lab and since we
wanted to replicate the findings of Experiment
#2 and #3 in Arntzen (2006) with different
delays (see below).
Furthermore, a distinction is also made between training structures and training protocols.
Imam (2006) has outlined the three different
protocols, i.e., (1) simple-to-complex, (2) complex-to-simple, and (3) simultaneous protocol.
We have used simultaneous protocol in the
current study since it was also used (Arntzen,
2006), and because simultaneous protocol is the
most used protocol in the stimulus equivalence
research.
Usually in matching to sample procedures,
each trial starts with a response to the sample
stimulus the sample which is followed by presentation of the comparisons, and sample and
the comparisons are present at the same time. In
a delayed matching-sample (DMTS) procedure,
a response to the sample stimulus is followed
by the disappearance of the sample, and the
presentation of the comparisons (0 s delay) or
n seconds before the comparisons appear. The
interval between offsetting the sample stimulus
and the onset of the comparison stimulus is
often called the retention interval. The term
refers to the fact that the sample stimulus has to
be remembered in order to facilitate discriminative responses to comparison stimuli (Arntzen,
2006). Nevin, Davison, Odum, and Shahan
(2007) distinguish between delayed matching
to sample with physical similar stimuli and arbitrary or symbolic stimuli, and the latter is the
case for stimulus equivalence research. Hence,
the reinforcement contingencies in delayed
matching-to-sample procedures apply to the
discriminative behavior at the presentation of
both the sample and comparison stimuli. The
retention interval is an independent variable
that can influence the different properties of
these relations. The retention interval may effectively impede the acquisition of conditioned
stimuli during training, but actually enhance
transfer and retention test performances (Vaidya
& Smith, 2006).
Remembering is often described by two
Retention Intervals in DMTS
classes of contingencies. One is simply the establishment of stimulus control of a response
through a three term contingency followed by
presentation of the stimulus at a later time.
The second contingency is often called problem solving, again initiated by establishing
stimulus control of a response. The difference
between contingencies is that reinforcement
subsequently is made contingent upon relevant
responses in the absence of the discriminative
stimulus (Palmer, 1991).
The delayed matching-to-sample procedure
has often been used to study ‘remembering’ in
nonhuman (Nevin et al., 2007; Sargisson &
White, 2001, 2007; Urcuioli & Zentall, 1986)
and humans (Williams, Johnston, & Saunders,
2006).There have been some diverging results
regarding the matching accuracy of increasing
retention intervals. For example, In an experiment with four youths with mental retardation,
Constantine and Sidman (1975) found that a
simultaneous presentation of sample and comparison gave better yields than delayed matching to sample (4-12 s). Furthermore, Torgrud
and Holborn (1989) found lower yields with
increasing retention intervals in children, and
Wright (2007) points out that in monkeys and
pigeons the performance decline as a function
of increasing delays and is about chance levels
at delays of one minute. On the other hand,
Blough (1959) in his classical experiment found
higher yields with longer retention intervals
for some birds. The birds that showed correct
responding during the retention intervals emitted sample specific responses. Furthermore, in
a study with budgerigars the results showed
that the birds emitted stereotypical behavior
sequences in the retention interval which correlated with correct performance. Later when
these behavior sequences were disrupted, the
number of corrected decreased, and one could
argue that such behavior sequences could
bridge the gap in delayed matching to sample
(Cleaveland, 1998).
Except for a few studies (e.g., Barnes,
Hegarty, & Smeets, 1997; Dickins & Kramo,
2003, as cited in Dickins, 2005; Fields, Reeve,
Varelas, Rosen, & Belanich, 1997; Lane &
Critchfield, 1998; Saunders, Chaney, & Mar-
179
quis, 2005; Tomanari, Sidman, Rubio, & Dube,
2006) research on stimulus equivalence has
been conducted using simultaneous matching
in a conditional discrimination procedure.
Lately, two studies (Arntzen, 2006; Vaidya &
Smith, 2006) have expanded our knowledge by
studying responding in accord with equivalence
as a function of simultaneous matching and
different retention intervals in delayed matching-to-sample tasks.
In Experiment 1 in Arntzen (2006), with a
MTO training structure the number of participants who responded in accord with equivalence
increased as function of increasing delays for the
participants starting with simultaneous matching. In Experiment 2 and 3 with an OTM training structure even with delays of nine seconds
the different delays did not affect the equivalence yields, e.g., all participants responded
in accord with equivalence in all conditions.
In a fourth experiment, the participants were
engaged in distracting tasks during the retention interval, and the results showed that none
of the participants responded in accord with
equivalence. It was argued that delayed matching to sample could evoke precurrent behavior,
that precurrent behavior may in turn facilitate
responding in accord with equivalence that
could be the case in the first three experiments.
On the other hand, distracting tasks might prevent the possibilities for rehearsal of mediating
behavior or precurrent behavior.
Vaidya and Smith (2006) replicated the
findings from Arntzen (2006) by using a experimental design with comparisons across
groups of participants rather than individual
participants and also with different stimuli since
they used common English and unfamiliar Portuguese and Czechoslovakian words as stimuli.
They used retention intervals of 0 s, 2 s, and
8 s both during training and testing and the
results showed that participants in the groups
with longer delays were more likely to respond
in accord with symmetry on the tests.
The purpose of the current study was to
replicate the findings from Experiment #2 and
#3 in Arntzen (2006). We wanted to investigate the probability of responding in accord
with equivalence in adult human participants
180
Erik Arntzen, Tommy Galaen, and Lars Rune Halvorsen
as a function of increasing and decreasing
sample-comparison delays (0 s delay, 6 s delay,
and 12 s delay) in a one-to-many conditional
discrimination procedure, and therefore, also to
expand the existing knowledge about DMTS
by increasing the maximum delay to 12 s. In
addition to an index of equivalence, measures
relevant to the readiness of class formation
include reaction times to comparison stimuli
and number of training trials and errors as a
function of increasing delays.
Method
Participants
Twenty Norwegian healthcare and social
workers were recruited to participate in the current experiment. Fourteen women and six men
participated. The age range was 20 to 45 years.
The participants were experimentally naïve, as
they had no previous experience with equivalence concepts or the abstract, arbitrary stimuli
used in the experiment. Every participant was
debriefed after the experiment.
Procedure
All participants were trained in individual
sessions according to an OTM training structure in DMTS format with three different
conditions, 0-second, 6-second, and 12-second
as retention intervals, followed by tests for
responding in accord with equivalence. Half
of the participants started with 0 s delay then
followed by 6 s and 12 s. The other half of
the participants started with 12 s delay then
followed by 6 s and 0 s. For each training and
testing condition, we used a new set of stimuli.
The different retention intervals were used only
during training, therefore, in the tests there
3
1
2
3
1
2
3
B
C
D
E
F
Stimulus material and presentation
In all training and test conditions, we used
3 three-member classes. The visual abstract,
arbitrary stimuli were Greek, Arabic, Cyrillic,
and Japanese alphabet symbols (as shown in
Figure 1).
A number on the top of the columns in each
table, indicate the different classes of stimuli.
The letters to the left of each row indicate the
class membership. The symbols in row ‘A’ were
always the node. During the stimulus presentation, the sample stimulus was always displayed
in a centre square, and the comparison stimuli
were presented in random corner squares.
2
A
Apparatus and software
An IBM Thinkpad X30 portable computer
with a 13” SVGA color monitor and a standard USB mouse pointing device was used in
the experimental sessions. The computer had
a 1200 MHz Mobile Intel Pentium 3 processor with 256 MB RAM. We used a software
program made by Psych Fusion Ltd to run the
experiment.
1
G
H
I
Figure 1. The stimuli used in each condition.
ABC were always 0 s, DEF were always 6 s, and GHI
were always 12 s.
181
Retention Intervals in DMTS
Table 1. The different training conditions and relations with the minimum number of trials per block are
Table 1. The different training conditions and relations with the minimum number of trials per
included in the table.
block are included
in the table.
Training Condition Stage
Relation
0-s delay
Training
A1B1,A2B2,A3B3
A1C1,A2C2,A3C3
Mixed Training
A1B1,A1C1,A2B2,
A2C2,A3B3,A3C3
18 trials (8 blocks)
Testing
A1B1,A1C1,A2B2,
A2C2,A3B3,A3C3,
B1A1,B1C1,B2A2,
B2C2,B3A3,B3C3,
C1A1,C1B1,C2A2,
C2B2,C3A3,C3B3
54 trials
Training
D1E1,D2E2,D3E3
D1F1,D2F2,D3F3
9 trials
9 trials
Mixed Training
D1E1,D1F1,D2E2,
D2F2,D3E3,D3F3
18 trials (8 blocks)
Testing
D1E1,D1F1,D2E2,
D2F2,D3E3,D3F3,
E1D1,E1F1,E2D2,
E2F2,E3D3,E3F3,
F1D1,F1E1,F2D2,
F2E2,F3D3,F3E3
54 trials
Training
G1H1,G2H2,G3H3
G1I1,G2I2,G3I3
9 trials
9 trials
Mixed Training
G1H1,G1I1,G2H2,
G2I2,G3H3,G3I3
18 trials (8 blocks)
Testing
G1H1,G1I1,G2H2,
G2I2,G3H3,G3I3,
H1G1,H1I1,H2G2,
H2I2,H3G3,H3I3,
I1G1,I1H1,I2G2,
I2H2,I3G3,I3H3
54 trials
6-s delay
12-s delay
was simultaneous matching. Breaks according
to individual preferences were accommodated
between each training-testing session. The experimental sessions were fulfilled in one day.1
Training and testing. All trials started with
the presentation of a sample stimulus. A click
with the pointing device on the stimulus produced a presentation of comparison stimuli in
either corner of the screen with a 02-, 6-, or
12- second delay. The inter-trial-interval was
1 s and the mouse cursor was reset to a fixed
1
Participant #1402 failed the 6-second delay condition and
had to resume the test about two weeks later, and participant
#1404 had an approximately six week break between the 6-second
trial condition and 12-second condition.
2
The 0-second condition was in fact configured with a 1
millisecond delay in the software, since the program requires a
number. However, for all practical purposes 1 millisecond appeared as a 0 s delay to the participant.
Minimum no. of trials
per block
9 trials
9 trials
position after each trial. In order to achieve
initial errorless training all training conditions
incorporated two initial training blocks (9 trials in each) presenting the correct comparison
stimulus only, however randomly presented in
any corner on the screen. Training block 3 (18
responses) presented 2 comparison stimuli per
trial while block 4 through to 10 (18 responses
in each block) presented 3 comparison stimuli
per trial. An incorrect response was followed by
a repeat trial of the specific sample-comparison
pair, presenting the comparison stimuli at a
random corner. Training block 1 through 6 all,
correct responses were followed by a 1 s display
of the word “Correct” on the screen. All incorrect responses produced the word “Incorrect”
for 1 s. The feedback was reduced through block
Erik Arntzen, Tommy Galaen, and Lars Rune Halvorsen
In a moment a word will briefly appear in the middle of the screen. It will
disappear and three other words4 will
appear. Choose 1 of the words in a corner
of the screen by clicking on it with the
mouse. During some stages of the experiment, the computer will NOT tell you if
your choices are correct or wrong. However, based on what you have learned so
far, you can get all of the tasks correct.
Please do your best to get everything
right. Thank you and good luck!
click as a response to both sample stimulus and
comparison stimulus, we were able to record
both reaction times (from the comparisons
were presented to a response on comparison)
and number of trials to criterion as dependent
measures. We have divided the training into
two parts. Part 1 is the introduction of training
trials and Part 2 is the trials during mixing and
fading of consequences.
Results
For the participants starting with 0 s delay,
nine out of ten participants met the equivalence
criterion during the 0 s condition, while ten
of ten participants both in the 6 s condition
and the 12 s conditions met the equivalence
criterion (as shown in upper panel Figure 2).
All of the participants responded in accord with
symmetry on all conditions. For the participants
starting with 12 s delay, nine out of ten partici-
10
9
Numberofparticipants
7 (75%), 8 (50%), and 9 (25%), ending with
the non-reinforced training block 10 and the
test block.
The test block consisted of a random mixing
54 trials of three types of trials, (1) testing for
directly trained relations, and both emergent
(2) symmetry relations and (3) global equivalence relations. 18 trials tested for responding
in accord with equivalence, 18 trials tested
for responding in accord with symmetry and
finally 18 trials tested directly trained relations. The criterion for responding in accord
with equivalence was defined as 90% correct
responding or more.
Instructions. All participants were initially
informed that the experiment aimed to explore
characteristics in the mechanics of human
learning, involving the use of a computer with
a standard mouse pointing device. The participants signed a written consent to the intended
application of the anonymous data. They were
also informed that they could quit participation
at any time, and, furthermore, that the duration
of the experiment could vary, mainly depending
on how correctly and quickly they responded,
but about three to four hours. The following
instructions3 were displayed on the screen before
the start of the experiment:
8
7
6
Sym
5
Eq
4
3
2
1
0
0s
3
The instructions were in English and translated for 3 nonEnglish speaking participants.
4
After the participants read the instructions we specified
that they would be presented with arbitrary symbols rather
than words.
12s
9
8
7
6
Sym
5
Eq
4
3
2
1
0
12s
We asked whether they felt the instructions
were clear and informative.
Dependent measures. By requiring a mouse-
6s
Delays
10
Numberofparticipants
182
6s
Delays
0s
Figure 2. The number of participants responding in accord with symmetry and equivalence for
each condition and starting with the shortest delay
is shown in the upper panel. In the lower panel are
shown the numbers for participants starting with
the longest delay.
183
Retention Intervals in DMTS
Table 2
Table 2 shows
number
trials tonumber
criterion and
for part 1and
and 2 number
of the training,
equivalence
and
Table
2. Table
2ofshows
ofnumber
trialsoftoerrors
criterion
of furthermore
errors forscores
partin1theand
2 of the
training,
furthermore
scores
theconditions.
equivalence and symmetry tests for each participant in all three
symmetry tests
for each participant
in allin
three
conditions.
0-sec delay
#
1401
Part 1 trials
Part 2 trials
Total Errors
Total Errors
162
6-sec delay
Em. relations
Sym
EQ
Part 1 trials
Total
Errors
21
90
0
18/18
18/18
90
3
Part 2 trials
Total
Errors
90
12-sec delay
Em. relations
Sym
EQ
Part 1 trials
Total
Errors
Part 2 trials
Total
Errors
Em. relations
Sym
EQ
1
18/18
18/18
72
0
90
0
18/18
18/18
18/18
1402
126
12
108
4
18/18
17/18
72
2
90
0
18/18
18/18
72
0
90
1
18/18
1403
144
17
90
3
18/18
18/18
90
3
108
2
18/18
18/18
72
1
90
1
18/18
18/18
1404
216
74
90
3
18/18
17/18
90
3
90
1
17/18
17/18
81
1
90
0
18/18
18/18
1405
198
39
108
5
18/18
15/18
72
0
90
0
18/18
18/18
72
0
90
0
17/18
18/18
1406
108
5
90
1
18/18
18/18
72
1
90
0
18/18
18/18
72
0
90
0
17/18
18/18
1407
234
73
90
1
18/18
18/18
72
0
90
1
18/18
18/18
72
0
90
0
17/18
18/18
1409
90
8
108
4
18/18
18/18
108
8
108
3
18/18
18/18
72
0
90
1
18/18
18/18
1410
234
33
90
2
18/18
17/18
90
5
90
1
18/18
18/18
90
7
90
2
18/18
18/18
1412
198
31
90
0
18/18
18/18
126
14
90
0
18/18
18/18
72
0
90
0
18/18
18/18
Table 3
Table 3 shows number of trials to criterion and number of errors for part 1 and 2 of the training, furthermore scores in the equivalence and
Table
3. Table 3 shows number of trials to criterion and number of errors for part 1 and 2 of the
symmetry tests
for each participant
in allin
three
training,
furthermore
scores
theconditions.
equivalence and symmetry tests for each participant in all three
conditions.
12 s delay
#
6 s delay
0 s delay
Part 1 trials
Part 2 trials
Em. relations
Part 1 trials
Part 2 trials
Em. relations
Part 1 trials
Part 2 trials
Em. relations
Total
Errors
Total
Errors
Sym
EQ
Total
Errors
Total
Errors
Sym
EQ
Total
Errors
Total
Errors
Sym
EQ
1413
108
19
90
0
18/18
17/18
72
0
90
2
18/18
18/18
72
0
90
2
18/18
18/18
1414
324
60
108
3
18/18
18/18
90
5
90
1
18/18
18/18
90
4
90
0
18/18
18/18
1415
144
22
90
1
18/18
18/18
72
1
90
1
18/18
18/18
72
0
90
2
18/18
18/18
1416
126
11
378
53
18/18
18/18
126
11
126
9
18/18
18/18
72
2
90
0
18/18
18/18
1417
144
15
90
3
18/18
18/18
108
6
90
1
18/18
18/18
72
0
90
1
18/18
18/18
1418
144
16
90
1
18/18
18/18
90
3
90
3
18/18
18/18
72
0
90
0
18/18
18/18
1419
216
30
126
8
18/18
17/18
72
0
90
1
18/18
18/18
72
1
90
1
18/18
18/18
1420
90
5
108
4
18/18
16/18
108
6
90
1
18/18
12/18
108
5
90
1
18/18
17/18
1421
180
40
90
0
18/18
18/18
90
3
90
1
18/18
18/18
72
1
90
0
18/18
18/18
1422
270
60
90
1
18/18
18/18
72
1
90
1
18/18
18/18
72
2
90
2
18/18
18/18
pants met the equivalence criterion during the
12 s and 6 s conditions and ten of ten in the 0s
condition (as shown in lower panel Figure 2).
All of the participants responded in accord with
symmetry on all conditions.
The individual data for participants starting
with 0 s delay showed that only participant
#1405 did not respond in accord with equivalence (see Table 2). For the participants starting
with 12 s delay (see Table 3), #1420 did not
respond in accord with equivalence with 12 s
and 6 delay.
As shown in Table 2, for the participants
starting with 0 s delay all required more trials
to meet criterion during Part 1 in the 0-second
condition than during Part 2. During the 0second delay condition Part 1, the participants
required from 0 to 164 extra trials to meet criterion, as opposed to Part 2 when 7 participants
required minimum trials and 3 participants
required 18 extra trials. For participant #1407,
the number of extra trials was reduced from
164 during Part 1 to 0 extra trials during Part
2. During Part 1 in the 6-second condition 4
184
Erik Arntzen, Tommy Galaen, and Lars Rune Halvorsen
participants reached criterion with the minimum of 72 trials, while 8 reached criterion in
Part 2 with the minimum of 90 trials. In the
12-second condition, 8 participants required
minimum number of trials to criterion in Part
1, and all participants met criterion in Part 2
with minimum number of trials. In the 12 s
condition Part 2, all participants required only
minimum training trials to meet criterion for
test trials. The number of errors is substantially
higher in the 0-second condition part 1, than
in part 2 and all subsequent training conditions. The number of training trials and errors
decrease as a function of increasing delays as
shown in Figure 3.
For participants starting with 12 s delay
all except #1416 and #1420 showed a higher
number of training trials in Part 1 than in Part
2 in the first condition with 12 s delay (see Table
3). None of the participants exceed the minimal
number of responses in the 0 s delay condition.
In sum for all participants, the number training
trials and errors decreased as function decreasing
delays (see Figure 4).
For the participants5 starting with 0 s delay
the median reaction times for both the 0 s and
6 s condition there is an increase from the five
last training trials to the five first symmetry test
trials and a subsequent decrease for the five last
training trials (see Figure 5). For equivalence
trials, there are also an increase from training
to test and then later decrease during the test,
and the changes (increase and decrease) are
more pronounced for equivalence trials compared to symmetry trials. In the 12 s condition,
there is no difference from training to test and
there is no difference between symmetry and
equivalence.
The median reaction time for all conditions
when starting with 12 s delay increased from the
five last training trials to the five first test trials
and decreased during the test (for the five last
test trials), and changes were more pronounced
for 12 s and 6 s, respectively (see Figure 6).
Decreasingdelays
990
900
810
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630
540
450
360
270
180
90
0
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Numberoftrainingtrials
810
720
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540
Part1oftraining
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Part2oftraining
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Numberoftrainingtrials
Increasingdelays
270
180
Part1oftraining
Part2oftraining
12s
90
0
0s
6s
Delays
6s
Delays
0s
12s
360
Numberoferrors
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280
240
200
Part1oftraining
160
Part2oftraining
Numberoferrors
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360
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Part1oftraining
160
Part2oftraining
120
80
120
40
80
0
12s
40
0
0s
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Delays
12s
Figure 3. The upper panel of Figure 3 shows the
number of training trials more than what is needed
to reach criterion for each condition. The lower panel
shows the number of errors for each condition.
6s
Delays
0s
Figure 4. The upper panel of Figure 4 shows the
number of training trials more than what is needed
to reach criterion for each condition. The lower panel
shows the number of errors for each condition.
5
Individual data could be presented if requested.
185
Retention Intervals in DMTS
Discussion
The current study was a replication and
an extension of the study by Arntzen (2006)
study on delayed matching to sample with different retention intervals that may influence
responding in accord with equivalence. In the
current study, we explored some effects of OTM
training structures providing DMTS tasks with
0, 6, and 12 s retention intervals in which ten
participants starting with 0 s delay and ten
participants starting with 12 s. The experiment
replicated the results from Experiment 2 and 3
in Arntzen (2006), supporting previously demonstrated MTS data (Arntzen & Holth, 1997,
2000). Furthermore, we extended knowledge of
retention intervals in DMTS by increasing the
interval to 12 s. The results showed that there
5
4,5
0sdelay
4
3,5
3
Baseline
2,5
Symmetry
2
Equivalence
1,5
1
0,5
was no difference in responding in accord with
equivalence for the participants starting with
either 0 s or 12 s, i.e., independent of order 9
of ten participants responded in accord with
equivalence on all conditions. Reaction time
data showed that the most typical pattern, increase from training and decreasing during the
test, was observed for the “equivalence” trials in
all conditions, and for the symmetry trials in
the conditions presented first independent of
retention interval.
Vaidya and Smith (2006) showed in a between subjects design or comparison between
groups design, that longer retention intervals
are likely to produce more symmetry-consistent
responses during testing. In the current experiment, all participants responded in accord with
symmetry after all training conditions.
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
Baseline
Symmetry
Equivalence
5lasttraining
0
5lasttraining
5firsttest
6sdelay
4
3,5
3
Baseline
2,5
Symmetry
2
Equivalence
1,5
1
0,5
6sdelay
Baseline
Symmetry
Equivalence
5lasttraining
5firsttest
12sdelay
Baseline
Symmetry
Equivalence
5lasttraining
5firsttest
5firsttest
5lasttest
Trials
5lasttest
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
5lasttest
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
0
5lasttraining
5firsttest
Trials
5lasttest
5
4,5
M
Medianseconds
12sdelay
5lasttest
Trials
Figure 5. Reaction time to comparison for the
five last training trials, the five first test trials, and the
five last test trials are shown for the three different
retention intervals.
5
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
0sdelay
Baseline
Symmetry
Equivalence
5lasttraining
5firsttest
5lasttest
Trials
Figure 6. Reaction time to comparison for the
five last training trials, the five first test trials, and the
five last test trials are shown for the three different
retention intervals.
186
Erik Arntzen, Tommy Galaen, and Lars Rune Halvorsen
Williams et al. (2006) mentioned two types
of competing stimulus control of comparison
selection – intratrial and intertrial sources of
stimulus control. Competing stimulus control
as other stimuli present at the time sample is
presented until the selection of the comparison
is labeled as intratrial sources. For example,
distracters presented during the delay could be
such competing stimuli. On the other hand, intertrial sources refer to stimuli conditions prior
to the current trial. This could for example lead
participants to select the same comparison as in
the preceding trial. Pigeons have selected the
same comparison as in the preceding trial, especially if that selection was reinforced (White,
Parkinson, Brown, & Wixted, 2004). The same
type of competing control has been seen in our
lab and in the current experiment when some of
the participants have mentioned that they have
selected a stimulus in a special position on the
screen and not under control by the samplecomparison matching. This could be one of
the reasons for the differences in the number
of training trials across participants.
As mentioned earlier, relatively few studies
have used delayed matching to sample training
in stimulus equivalence research. Thus, those
studies have used one fixed retention interval
during the experiment, not varied intervals
along a dimension as in the current study,
Arntzen (2006) in a within-subject design, and
Vaidya and Smith (2006) in a between group
design. For example, Barnes et al. (1997) had
a sample-comparison delay of 0.4 s retention
interval and trained equivalence-equivalence
relations in adults and children. Fields et al.
(1997) used a delayed matching to sample with
a retention interval of 0.25 s during testing as
part of a correction procedure for participants
not responding in accord with equivalence in
a stimulus-pairing yes/no format. Lane and
Critchfield (1998) trained four 4-member
classes in six undergraduates with a delayed
matching to sample procedure, with a retention
interval of 0.25 s. In Experiment 2 in Saunders
et al. (2005), six senior citizens were trained and
tested with 0-s delayed matching to sample.
Results showed that there was less number of
training trials to criterion and a higher yield of
responding in accord with equivalence during
testing than in Experiment 1 with simultaneous matching. They discuss the possibility of
precurrent behavior as an explanation for the
higher yields during delayed matching to sample
(see also Arntzen, 2006; Holth & Arntzen,
1998a, 2000). Skinner (1968) gave an example
of teaching a precurrent response directly in a
matching to sample task, as looking at sample
and pressing it. Such attending behavior seems
to be even more important in delayed matching to sample, and may be necessary for solving
the problem, i.e., correct matching. It could be
that the retention interval between sample and
comparison stimuli will increase the possibilities for the participants to attend to the sample
stimulus. Experiments with pigeons have shown
that pecking that increase the sample duration
had a solid effect on the pigeons’ accuracy of
delayed matching (Spetch & Treit, 1986), others have explicitly mentioned that a delay could
promote observing or having the participants
looking at the sample (Lane & Critchfield,
1998). Dinsmoor (1985) wrote about behavior
known as observing, for example looking at
and focusing on the stimulus object, touching
it, tasting it when he discussed attention, and
he said “…to complete the picture I think we
are obliged to consider analogous processes occurring further along in the sequence of events,
presumably in the neural tissue, and commonly
known as attention. The processes involved in
attention are not as readily accessible to observation as the more peripheral adjustments, but it is
my hope and my working hypothesis that they
obey similar principles. Otherwise, the study of
attention may prove extremely difficult. From
the behavioral level it can only be approached
indirectly, and we will face the arduous task
of distinguishing its behavioral effects in each
instance from those to be attributed to changes
in observing” (p. 365). And also as Nevin et al.
(2007) have mentioned – “… attending to the
components of a conditional discrimination
could be construed as umeasured or covert
behavior …” (p. 286).
In a delayed matching to sample procedure,
the retention intervals could facilitate increasing rehearsal opportunities. For example, from
Retention Intervals in DMTS
the pigeon literature, Blough (1959) wrote
that he observed that some pigeons emitted
sample-specific, stereotypical responses, similar
to rehearsal, during the delay interval. The suggestion is supported by Arntzen’s Experiment
4 (2006) that incorporated distracting tasks
during the 3-second retention interval, making
it difficult to engage in rehearsal. None of the
participants responded in accord with equivalence during subsequent tests. Furthermore,
Nevin et al. (2007) have proposed a theory of
attending and reinforcement in conditional
discrimination procedures where they have put
in terms for disruption of attending in delayed
matching to sample.
On the other hand, Vaidya and Smith
(2006) found that 1/3 of the participants
reported intraverbal naming, but only some
of them responded in accord with symmetry.
The role of naming has been discussed within
stimulus equivalence research for a long time
and some researchers have concluded that naming (at least common naming) is not necessary
and naming responses could be a product of the
naming itself (e.g., Sidman, Willson-Morris, &
Kirk, 1986), and could not be possible because
of time restrictions (Tomanari et al., 2006).
First, different types other than common naming as rehearsal have been discussed elsewhere
(e.g., Holth & Arntzen, 1998b). Second, it is
obvious that the task in a delayed matching to
sample differ from a simultaneous matching
to sample with respect to time gap in DMTS
which must filled with some behavior.
Rehearsal may represent an example of
mediating behavior as it occurs in a consistent
relation to correct responses and is maintained
by making success more likely (Catania, 2007).
Mediating behavior is termed as precurrent if it
actually results in the target response. For example, if rehearsal during the retention interval
in a DMTS-procedure actually contributes to
responding in accord with equivalence, it has
acted as precurrent behavior (Arntzen, 2006),
and may in fact constitute remembering. The
contingencies of remembering is described as
reconstruction of experiences, as we do not
actually remember stimuli themselves but rather
“....our own behavior toward those stimuli”
187
(Catania, 2007, p. 321). In order to account
for the phenomenon of remembering in basic
behavioral terms, Catania suggests we do not
try to “....follow the stimulus into the organism; rather we must discover how to characterize the organism’s behavior with respect to
the stimulus” (Catania, 2007, p. 325). The
contingency of remembering or precurrent behavior may lend itself to this strategy through
experimental studies on responding in accord
with equivalence as a function of increased
retention intervals.
With respect to the issue of precurrent behavior, a notable reaction time pattern seems
to emerge from MTS research and warrants
attention. Results often reveal increased reaction
times during the first five test trials compared to
the last five training trials and usually decrease
somewhat during the test procedure. Reaction
time variances may suggest that comparison
selection is not directly under sample stimulus
control during the first few test trials. Initial
equivalence test trials may occasion some sort
of precurrent behavior that in effect creates the
actual discriminative stimulus, i.e. naming or
intraverbals (e.g., Arntzen, 2004, 2006; Holth
& Arntzen, 2000).
Reaction times or latencies have been
seen as an important feature within stimulus
equivalence research besides responding in accord with equivalence (Dymond & Rehfeldt,
2001; Spencer & Chase, 1996). Actually, there
are differences in the equivalence literature on
how latency or reaction time is measured. Some
have measured latency or reaction time from
the presentation of comparison to a response
to the comparison (e.g., Arntzen & Holth,
1997; Bentall, Dickins, & Fox, 1993; O’Hora,
Roche, Barnes-Holmes, & Smeets, 2002; Tomanari et al., 2006; Wulfert & Hayes, 1988),
while others have measured latency as the time
from responding to the sample and selecting
the comparison (Imam, 2001, 2003, 2006;
Spencer & Chase, 1996). In a simultaneous
matching condition this should not make a
difference as long as it is a requirement of a
response to sample stimulus as in our lab. When
the sample is presented without requirement
of any response one or two seconds before the
188
Erik Arntzen, Tommy Galaen, and Lars Rune Halvorsen
comparison (e.g., O’Hora et al., 2002; Wulfert
& Hayes, 1988) this could make a difference.
It has been speculated that such an interval
between the sample and comparison would prepare the participants to respond and therefore,
wipe out the differences between reaction time
to baseline trials and symmetry trials (Spencer
& Chase, 1996). The reaction time results are in
accord with other experiments that have shown
that latency are longer for “equivalence” trials
compared to “symmetry” trials (Bentall et al.,
1993; Bentall, Jones, & Dickins, 1999; Imam,
2001; Saunders & McEntee, 2004; Spencer &
Chase, 1996; Tomanari et al., 2006).
Reaction time data may be of relevance to
the question of whether initial test trials force
some sort of precurrent behavior. The elevated
reaction times during the first few test trials
may be accounted for by problem solving
behavior that facilitates demonstrations of
emergent equivalence relations and the decrease
in reaction times during the test could indicate
a shift to more direct stimulus control (see
Donahoe & Palmer, 1994). The suggestion is
supported by experiments that effectively prevented responding in accord with equivalence
by providing reaction time restrictions during
testing (Holth & Arntzen, 2000). For example,
has Palmer (2004) argued that reaction times
could be important measure as an index for
covert behavior. Schlund, Hoehn-Saric, and
Cataldo (2007) discuss what sort of neural activity that could underlie covert behavior when
they conclude that “… the findings extend the
role of frontal-subcortical and frontal-partietal
networks to derived conditional relations and
suggests that regional involvement varies with
the type of derived conditional relation.” (p.
287), but it is not clear what activity is related
to stimulus presentations and what is related to
reinforcement presentations.
Some studies, mainly with identity matching, have shown that matching accuracy decreases as a function of increases in the retention
interval. It has been argued that reduced samplestimulus control of comparison selection could
be the reason for the decreased accuracy at
longer retention intervals (e.g., Williams et al.,
2006). The results are in contrast to findings
from the current experiment and also to Arntzen (2006) and Vaidya and Smith (2006), and
it is possible that the differences could be due
to participants’ characteristics since Williams
et al. are referring to studies with participants
with mental retardation. Another variable that
could influence is that in Williams et al. (2006)
it is identity matching while in the others there
is arbitrary matching. Furthermore, it could
be that differences between the current study
and Experiment 2 and 3 in Arntzen (2006)
with respect to number of training trials and
errors could be an effect of order and not as a
function of increasing retention interval, since
in the current experiment number of training
trials and errors decrease as a function of the
sequence of retention intervals presented to
the participants.
The duration of the experiment is longer
when there is a delay as in delayed matchingto-sample procedures compared simultaneous
matching, and for the participants an increase
from 9 to 12 s does make a noticeable difference
with respect of duration. It could be interesting
to extend the interval even longer for example
to 21 or 24 s (we have earlier done experiments with 0, 1, 3 etc up to 9 s), but such an
increase will affect the duration of the length
of experiment even more. Such time consuming experiments could be difficult to do with
humans especially in within-subjects designs,
but is often used with pigeons. On the other
hand it seems very important to study the effects of different delays, and also longer ones,
because in the real world it is obvious that there
will be occasions with shorter or longer delays
between stimulus presentations. So in spite of
the possible “fatigue” effects it is important
to do further analyses of different retention
interval. One way to do this could be by using
titrating delays. Then retention intervals could
gradually be increased or decreasing depending
on correct or incorrect responding during one
experimental session.
In sum, the results from the current study
have contributed to knowledge regarding
procedural variables that might influence the
emergence of equivalence relations by replicating Experiment 2 and 3 in Arntzen (2006). The
Retention Intervals in DMTS
experiment demonstrated that OTM facilitates
responding in accord with equivalence after
extended DMTS training. Results showed
that it is possible to increase retention intervals
during training to 12 seconds while maintaining responding in accord with equivalence in
the subsequent test block. It seems relevant to
study in a future experiment the effects of using
MTO with different retention intervals and also
to include different retention intervals during
the tests to provide more coherent training and
testing conditions, since it could be that different covert behavior acquired during 12 s delay
in training and simultaneous matching during
testing. In addition, if we look at studies with
pigeons one variable that could be important
to study is the use of titrating delays instead of
fixed retention intervals. Since with titrating
delays the participant could increase or decrease
the delays dependent on it's own behavior or
responding. Furthermore, it could be difficult
to compare results of different published experiments within stimulus equivalence research due
to the fact that a number of variables vary or are
not mentioned at all. For example, the kinds of
instructions given, length of inter trial intervals,
type of stimuli, two vs. three choice, requirements of a response to sample stimulus or not
etc. (Arntzen, 2007) seem to be important to
study in future experiments.
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