Acquisition and Maintenance of Visual-Visual and Visual ... - CiteSeerX

5 downloads 3029 Views 383KB Size Report
The stimulus equivalence literature has dem- onstrated that a multimodal, or cross-modal approach to teaching individuals equivalence classes may be both ...
EUROPEAN JOURNAL OF BEHAVIOR ANALYSIS

2006, 7, 87 - 98

NUMBER 1 (SUMMER 2006)

87

Acquisition and Maintenance of Visual-Visual and Visual-Olfactory Equivalence Classes Daniel M. Fienup and Mark R. Dixon Southern Illinois University

Cross-modal equivalence formation has been of interest to behavior analysts recently because of its potential benefits over typical visual based learning. The present experiment was conducted to examine this possibility with the acquisition and maintenance of visual-olfactory classes of stimuli as compared to visual-visual classes of stimuli. Four college students completed the training and testing of visual-visual and visual-olfactory sets of stimuli including three maintenance probes followed by training and testing for merging of the classes. Results demonstrated a slight advantage in acquisition and maintenance for the visual-olfactory set of stimuli. Implications for these findings in applied settings and directions for future research are suggested. Key words: stimulus equivalence, cross-modal, visual-olfactory, college students.

The stimulus equivalence literature has demonstrated that a multimodal, or cross-modal approach to teaching individuals equivalence classes may be both quicker in terms of acquisition (Green, 1990; Hayes, Tilley, & Hayes, 1988; Rehfeldt & Dixon, 2005; Smeets & Barnes-Holmes, 2005; Taylor & O’Reilly, 2000) and durability over time (Rehfeldt & Dixon, 2005) than teaching these classes using a single modality. Yet, these studies have been primarily grounded on research findings using visual-visual and visual-auditory stimuli. Other sensory modalities, and their possible correspondence with visual-auditory stimuli characteristics are less known. One of the first deviations from teaching visual-auditory cross-modal equivalence class comparisons was conducted by Hayes et al. (1988) when they examined the taste modality: gustatory. The stimuli for this experiment included nine Mandarin characters (visual stimuli), and three gustatory stimuli (salt-saturated water, sugar-saturated water, and unsweetened lemon juice). In the first experiment, half of the participants were taught conditional discriminations with

strictly visual stimuli. The second group of participants was taught conditional discriminations using a gustatory stimulus as the sample stimuli, and visual stimuli as comparison stimuli. The results showed that all participants demonstrated equivalence relations after one or two training sessions; however, all participants in the gustatory condition scored 100% on all equivalence tests after the first training, while only two of six participants scored this high in the visual condition. A second experiment was run to replicate the findings of the first experiment. Similar results were found: all the participants in the gustatory condition scored 100% on the equivalence tests following training. While all participants in the visual condition scored 100% on the second and third equivalence tests, all three participants scored less than 100% on the first test. Another finding from both experiments was that fewer trials were needed in training for the gustatory condition than the visual condition. Annett and Leslie (1995) conducted another study that deviated from the traditional sensory modalities of stimulus equivalence. This study examined equivalence class formation using visual and olfactory (smell) stimuli. Odor, or olfactory stimuli, served as comparison stimuli. The olfactory stimuli consisted of commercially available

Address all correspondence to: Dr. Mark R. Dixon, Behavior Analysis and Therapy, Rehabilitation Institute, Southern Illinois University, Carbondale, IL 62901-4609. E-mail: [email protected] 87

88

Daniel M. Fienup and Mark R. Dixon

perfumes, and common, easy to discriminate odors. The B stimuli were letters that made up nonsense syllables and the C stimuli were abstract line drawings. Of the fourteen participants who made it to the testing phase, thirteen developed equivalence classes. While Annett and Leslie (1995) demonstrated that visual-olfactory equivalence classes could develop, no comparisons have yet been made to traditional visual-visual classes. The formation of tactile equivalence classes has also been examined using auditory and tactile comparisons (Bush, 1993), but yet again no comparisons of acquisition and maintenance of this approach to visual-visual classes have been made. A recent study by Rehfeldt and Dixon (2005) examined the acquisition and durability of gustatory-visual and visual-visual classes. Their results supported gustatory-visual findings on speed of acquisition for cross-modal classes compared to unimodal classes, as well as showed the gustatory-visual class maintained greater composition, or higher scores on the equivalence test, during maintenance probes. To date, no such attempt like this has been made using visual-olfactory stimuli, in terms of comparing acquisition and maintenance. Another important topic that has not been explored with visual-olfactory stimuli is class mergers. The question still remains as to whether or not cross modal and unimodal equivalence classes can be expanded in to one larger class of stimuli, or merged (Sidman, 1994), by training participants to match one stimulus from one class to one stimulus of another class. This is important because if participants can merge cross-modal equivalence classes, then large classes of relations can be formed using minimal trained relations. Furthermore, no study has explored the possibility of class merger with visual-olfactory stimuli following maintenance probes of a single class formation. Class merger research has not received much attention and many questions are still left unanswered. Therefore the purpose of the present study was to empirically answer these questions. The present study looked at developing equivalence classes (i.e., four 3-member classes, organized into 2 sets) in college students. Both visual-visual and visual-olfactory sets of stimuli

were trained followed by a test for “derived” relations using a one to many protocol. The test for “derived” relations sought to establish whether participants were able to relate two stimuli within a class that had never been directly paired. By looking at the number of blocks of trials completed to finish training we were able examine acquisition rates of the two types of classes as well as examine maintenance rates of these classes over a three-week period. Afterwards, one stimulus from each visual-visual class and one stimulus from each visual-olfactory class were trained together to potentially expand class membership from three stimuli to six stimuli. A test of the merger followed to see if individuals’ class formation did indeed expand. Method Participants and Setting

Four college students, two males and two females, between the ages of 21 and 25, participated in this experiment. Three of the participants were graduate students while one participant was an undergraduate student. All participants were recruited by word of mouth. Each participant completed initial training that took approximately 60 minutes. Maintenance testing sessions were conducted once a week for three weeks followed by a merger training and testing period. All sessions were conducted in one of two quiet rooms, approximately 10 feet by 15 feet. Stimulus Materials

Figure 1 displays the two sets of stimuli that were used in the experiment. Arbitrary stimuli and relations were chosen so as to reduce the probability of participants having preexisting relations between the stimuli. Each set of stimuli included three classes of stimuli, resulting in six total classes of stimuli. Stimulus Set 1 included olfactory and visual stimuli. The olfactory stimuli served as sample stimuli, and visual stimuli served as comparison stimuli. The olfactory stimuli for Set 1 were distinctive scents that were saturated in a cotton tube sock and placed into a clear plastic squeeze bottle. Bottles were kept at room temperature throughout the duration of the study. All three bottles were identical in size and shape and

89

Cross-Modal Equivalence Classes

Visual-Olfactory Set B stimuli

A stimuli

Class 1

Rubbing Alcohol

Class 2

Vinegar

Class 3

Cinnamon

C stimuli

Visual-Visual Set B stimuli Class 1

Class 2

Class 3

Figure 1. The stimuli for the experiment.

A stimuli

C stimuli

90

Daniel M. Fienup and Mark R. Dixon

were opaque such that no distinguishing features idiosyncratic to the three scents or the sock could be discriminated by the participants. The plastic squeeze bottle resembled a ketchup bottle and was approximately 7 inches tall and 2 inches wide. All olfactory stimuli were identical in appearance. Stimuli were placed in front of the participant and instructed to place his or her nose near the bottle and smell the scent. Approximately every three trials, which may have included exposure to more than one scent as a consequence of stimulus randomization, the participants were instructed to smell coffee beans to help reduce carry-over affects between scents. The coffee beans were placed in an 8 once metal cup. Set 2 consisted of all visual stimuli, specifically where the comparison stimuli and the sample stimulus were visual. Both stimulus sets were denoted as A1, A2, A3, B1, B2, B3, C1, C2, and C3. In the visual-olfactory set (Set 1), the “A” stimuli were distinctive scents (Rubbing Alcohol, Vinegar, and Cinnamon). Each of these scents was soaked into a adult male’s sock by emerging the sock in the liquid. The “B” and “C” stimuli were patterns found on sweater, chairs, and rugs. In the visual-visual set (Set 2), the “A” stimuli were pictures of objects (large rocks, small rocks, and cement). The “B” and “C” stimuli were patterns found on sweaters, chairs, and rugs. The “B” and “C” stimuli from Set 1 and 2 were different. All visual stimuli were printed on 5x7 cards and laminated. All stimuli were presented on a board that was 2 feet by 3 feet. On the board, square outlines were drawn to indicate where the stimuli were to be placed. The board was used to ensure consistency of presentation of stimuli across trials. Research Design

A multiple probe design across stimulus sets, where B-C and C-B pretests serve as the baseline, was used followed by training of either Set 1 (visual-olfactory) or Set 2 (visual-visual). Upon completion of all training and testing of one of the sets, the other stimulus set was trained and tested. Specific order of the two sets’ training and testing was counterbalanced across participants. Afterwards, three follow-up tests for both sets were conducted. Following this phase, the participants were trained to merge the sets of stimuli and

then were tested on “derived” relations. Figure 2 shows the flow-chart for the experiment. Interobserver Reliability (IOR) was calculated for a minimum of 25% of the trials conducted. The following equation was used to determine IOR: [Agreements/(Agreements + Disagreements)] *100%. The resulting IOR was 99.7%, conducted on 59% of the trials conducted. Procedure

Phase 1: Equivalence Test (pre-test). The experiment started by pre-testing the individuals on the B-C and C-B relations. At this point, participants were tested on both Set 1 and Set 2 equivalence relations to assess if the participants could already form these relations. In the pre-test, one sample stimulus was presented on the bottom of the board with three comparison stimuli positioned above. The participants were instructed to “Select one picture on the top that goes with the picture on the bottom.” The researcher recorded the first comparison stimulus touched by the participant. For the pretest and all other tests, no consequences were delivered for correct or incorrect answers. The pretest consisted of 24 trials. There were four trials of each of the three B-C and three C-B relations in the pretest that were randomly generated and held constant across subjects. The positions of the comparison stimuli were randomized for each trial. Phase 2: Training (Either Set 1 or Set 2) & Testing. Half of the participants started training with Set 1, while the other half of the participants started with training of Set 2. A-B and A-C Training. In the visual-olfactory set of stimuli the participants were taught to match distinctive scents, or smells, to patterns printed on cards. For the visual-visual set of stimuli, participants were taught to match pictures of objects to patterns. The researcher recorded the first comparison stimulus touched by the participant. For both classes of stimuli, verbal feedback (“good job”, “that is correct”) was delivered after every correct response. Incorrect responses received no feedback, the instructor simply moved on to the next trial. Responses for this training phase (both visual-visual and visual-olfactory) were divided into blocks of nine trials. Criterion for mastery during these two phases was a score of 8/9 correct responses for a block of trials or better.

91

Cross-Modal Equivalence Classes

Mixed Training. The relations trained in this phase were identical to the relations trained during the A-B and A-C sessions yet presenting in a mixed

fashion across trials. Criterion for mastery for this phase was a score of 16/18 correct responses for a block of trials or better. Phase 4: Follow-up Test (3 Follow-ups) 1

Phase 1: Pre-Test Set 1 B-C C-B

Set 2 C-B B-C

Phase 2: Training (Either Set 1 or Set 2) & Post-Testing

Week Apart -Same as Pre-Test Set 1 Set 2 B-C C-B C-B B-C Phase 5: Set Merger Training B (Set 1) B (Set 2)

l l

Phase 6: Test Set Merger

A-B A-C Mix Test Phase 3: Pre-Testing, Training, & PostTesting (Remaining Set) Set 1 B-C C-B

or

Set 2 C-B B-C

B (Set 1) l C (Set 2) C (Set 2) l B (Set 1) B (Set 1) l A (Set 2) A (Set 2) l B (Set 1) A (Set 1) l C (Set 2) C (Set 2) l A (Set 1) A (Set 1) l B (Set 2) B (Set 2) l A (Set 1) A (Set 1) l A (Set 2) A (Set 2) l A (Set 1) C (Set 1) l C (Set 2) C (Set 2) l C (Set 1) C (Set 1) l B (Set 2) B (Set 2) l C (Set 1) C (Set 1) l A (Set 2) A (Set 2) l C (Set 1) Phase 7: Sorting Test

A-B A-C Mix Test

Figure 2. The flow-chart for the experiment.

B (Set 2) B (Set 1)

92

Daniel M. Fienup and Mark R. Dixon

Equivalence Testing (post-test). The post-test was identical to the pretest, consisting of 24 B-C and C-B trials. The criteria for demonstrating if someone demonstrated equivalence was a score of 21 (87%) or better (Rehfeldt & Dixon, 2005). Phase 3: Pretest, Training, & Testing. During this phase, the participants first completed a pretest on the set of stimuli that had not been trained in Phase 2. Next, participants completed the training and testing for this set of stimuli. The procedure for this phase was exactly as stated in Phase 2, except that participants who were trained and tested with Set 1 in Phase 2 were trained and tested with Set 2 stimuli. Participants who were trained and tested on Set 2 during Phase 2 were trained and tested with Set 1 stimuli. Phase 4: Follow-Up Testing. This phase started two days after the completion of Phase 3. Follow-up testing occurred one time a week for three weeks resulting in three follow-up tests completed by participants. The follow-up tests were identical to the pre and post-tests in regards to stimuli and procedure. Phase 5: Class Merger. The participants were trained to match the B stimuli (B1, B2, and B3) from Set 1 with the B stimuli (B1, B2, and B3) from Set 2. Both B (Set1) – B (Set 2) and B (Set 2) – B (Set 1) relations were trained as described above. Criterion for mastery for this phase was a score of 16/18 correct responses. Phase 6: Test Class Merger. During this phase, the participants were tested on whether Sets 1 and 2 merged. All relations between the two classes were tested. The merger test included three trials of every possible relation. This resulted in a total of 144 trials. Phase 7: Sorting Test. After the completion of Phase 6, participants were asked to complete a sorting task similar to that reported by Green (1990) as an alternative technique to test for stimulus class membership. Participants were given the actual stimuli used during the experiment and asked to “place the objects in three piles.” No feedback or consequences were delivered followed completion of this task.

Results All participants were able to complete the training and demonstrate equivalence on at least one of the sets of stimuli, often on both. Figure 3 shows Pretest, Training, Posttest, and Follow-up data for Cornelius. He completed A-B training in two blocks of trials and A-C training in two blocks of trials. Cornelius completed mixed training in three blocks of trials and scored 75% correct on the posttest, which did not meet the criteria for demonstrating equivalence. On the three follow-up tests Cornelius scored 71%, 79%, and 46% correct respectively. For the visual-olfactory set, Cornelius scored 0% correct on the first pretest and 50% correct on the second pretest. He completed A-B training in one block of trials, A-C training in two blocks of trials and mixed training in one block of trials. Cornelius’ posttest score was 100% correct, and his follow-up scores were all maintained at 100% correct. In terms of training, Cornelius completed the training for the visual-olfactory class in fewer blocks of trials (4) than the visual-visual class (7 blocks of trials). Furthermore, he did not meet criteria for demonstrating equivalence on the visual-visual set while he did meet this criterion for the visualolfactory set. Figure 4 shows Pretest, Training, Posttest, and Follow-up data for Zira. On the pretest for the visual-visual set, Zira scored 29% correct, while on the visual-olfactory pretest she scored 33% and 33% correct, respectively. Zira demonstrated no differences in acquisition of the two sets, acquiring A-B relations in both sets in two blocks of trials. She also completed A-C training for both sets in two blocks of trials. Zira completed mixed training for both sets of stimuli in one block of trials followed by a posttest score of 100% correct for both sets of stimuli. Zira maintained follow-up tests scores for both classes at 100% correct. Figure 5 shows Pretest, Training, Posttest, and Follow-up data for Taylor. Taylor was first trained on the visual-olfactory set where he scored a 63% correct on the pretest. Taylor completed the A-B training for this set in two blocks of trials, the AC training in one blocks of trials, and the mixed training in two blocks of trials followed by a score of 96% correct on the posttest. The follow-up test

93

Cross-Modal Equivalence Classes

Percentage Correct

Training and Tetsing Data for Cornelius 100 90 80 70 60 50 40 30 20 10 0 -10

Pre A-B

Mixed

A-C

Post

Follow-up

Visual-Visual

1

2

100 90 80 70 60 50 40 30 20 10 0 -10

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

6

7

8

9

10 11 12 13 14 15 16 17 18

Visual-Olfactory

1

2

3

4

5

Blocks of of Data Trials Blocks Figure 3. Pretest, Training, Posttest, and Follow-up data for Cornelius.

Percentage Correct

Training and Testing Data for Zira 100 90 80 70 60 50 40 30 20 10 0 -10

18

Pre

A-B

A-C

Follow-up

Mixed Post

Visual-Olfactory

1

100 90 80 70 60 50 40 30 20 10 0 -10

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

5

6

7

8

9

10

11

12

13

14

15

16

17

Visual-Visual

1

2

3

4

Blocks of of Data Trials Blocks Figure 4. Pretest, Training, Posttest, and Follow-up data for Zira.

94

Daniel M. Fienup and Mark R. Dixon

Percentage Correct

Training and Testing Data for Taylor 100 90 80 70 60 50 40 30 20 10 0 -10

Pre

A -B

A-C

Mixed

Follow-up

Post

Visual-Olfactory

1

2

100 90 80 70 60 50 40 30 20 10 0 -10

3

4

5

6

7

8

9

10

11

12

13

14

15

16

5

6

7

8

9

10

11

12

13

14

15

16

Visual-Visual

1

2

3

4

Blocks of Trials Blocks of Data Figure 5. Pretest, Training, Posttest, and Follow-up data for Taylor.

Percentage Correct

Training and Testing Data for Nova 100 90 80 70 60 50 40 30 20 10 0 -10

Pre

A-B

A-C

Mixed

Post

Follow-up

Visual-Visual

1

2

100 90 80 70 60 50 40 30 20 10 0 -10

3

4

5

6

7

8

9

10

11

12

13

14

15

16

6

7

8

9

10

11

12

13

14

15

16

Visual-Olfactory

1

2

3

4

5

Blocks Blocks of of Data Trials

Figure 6. Pretest, Training, Posttest, and Follow-up data for Nova.

95

Cross-Modal Equivalence Classes

100 90 80 70 60 50 40 30 20 10 0

Merger Training

Merger Data Merger Test

2nd 3rd

Percentage Correct

Merger Training

2

3

4

5

6

Merger Test

Merger Test

Sorting Task

3rd 3rd

2nd 3rd

1st 3rd

Zira Merger Training

2

3

Merger Test

4

2

Merger Training

Taylor

3

4

Merger Test

2

6

Sorting Task

3

3rd 3rd

2nd 3rd

5

6

Merger Test

1st 3rd

1

5

Merger Test

1st 3rd 1

100 90 80 70 60 50 40 30 20 10 0

3rd 3rd

Cornelius

1

100 90 80 70 60 50 40 30 20 10 0

Sorting Task

1st 3rd

1

100 90 80 70 60 50 40 30 20 10 0

Merger Test

4

2nd 3rd

Sorting Task

3rd 3rd

Nova 5

Sessions Figure 7. The merger training and testing data for each participant.

6

7

96

Daniel M. Fienup and Mark R. Dixon

scores for Taylor were 88%, 100%, and 100% correct, respectively. For the visual-visual set, Taylor scored 21% correct on the first pretest and 13% correct on the second pretest. For this set, Taylor completed A-B training in one block of trials, A-C training in two blocks of trials, and mixed training in one block of trials. Taylor’s posttest score for the visual-visual set was 92% correct, with follow-up scores of 92%, 67%, and 100% correct. Taylor did complete the training for the visual-visual set in one less block of trials than the visual-olfactory set; however, Taylor’s average equivalence test score for the visual-olfactory set was higher. Figure 6 shows Pretest, Training, Posttest, and Follow-up data for Nova. Nova completed training and testing for the visual-visual set first and scored 8% correct on the pretest for this set. She completed A-B training in two blocks of trials, A-C training in two blocks of trials, and mixed training in one block of trials. Her posttest score was 100% correct, with follow-up scores of 100%, 83%, and 100% correct. For the visual-olfactory set, Nova scored 8% and 0% correct, respectively. For this set, Nova completed A-B training in two blocks of trials, A-C training in one block of trials, and mixed training in one block of trials. Nova’s posttest score for the visual-olfactory set was 100% correct, with follow-up scores of 100%, 21%, and 33% correct. Due to low maintenance rates, Cornelius and Nova both required retraining on one of the sets of stimuli in order to make the two sets of stimuli meet criteria for demonstrating equivalence. Cornelius required retraining on the visual-visual set of stimuli where he scored a 46% correct on the third follow-up equivalence test. He completed the mixed training for this set in two blocks of trials and scored 100% correct on the posttest following mixed training. Nova’s follow-up test scores for the visual-olfactory class did not meet the criterion for demonstrating equivalence, so retraining of this class was completed before the classes were merged. Nova completed the mixed training for the visual-olfactory training in one block of trials, achieving a score of 89% correct. Nova scored 100% correct on the visual-olfactory posttest following retraining. After the completion of training and any

necessary retraining, the participants completed merger training and a test of the merged classes. Figure 7 shows the merger training and testing data for each participant. Cornelius completed the merger training in one block of trials. On the merger test, Cornelius scored 92% correct. By dividing up the test into three sections of 48 trials, Cornelius scored 75% correct on the first third and 100% correct on the second and third parts of the test. When given the sorting task for the class merger he scored 100% correct. Zira completed the merger training in one block of 18 trials. On the merger test she scored 61% correct. Dividing the test up into three parts, Zira scored a 46% correct on the first part, 65% correct on the second part, and 73% correct on the third part of the merger test. During the sorting task, Zira scored 89% correct, mixing up two of the A stimuli from visual-visual class. Taylor completed the merger training in one block of trials. On the merger test he scored 57% correct. Dividing the test up into three sections, Taylor scored a 40% correct on the first section, 60% correct on the second section, and 73% correct on the third section. During the sorting task, Taylor obtained a score of 100% correct, placing all stimuli in their respective classes. Nova completed the merger training in two blocks of trials. On the merger test she scored 53% correct. Dividing the test up into three parts, Nova scored a 42% on the first third, 48% on the second third, and 67% correct on the last third of the merger test. During the sorting task, Nova scored an 89% correct, mixing up two of the C stimuli from the visual-visual class. Discussion All subjects were able to complete the training for both visual-visual and visual-olfactory sets of stimuli and demonstrate “derived” relations. The present finding that all participants were able to demonstrate visual-olfactory equivalence classes, supports previous research with gustatory stimuli by Annett and Leslie (1995). Two participants completed the training for the visual-olfactory set of stimuli with less errors than the visual-visual set, while one participant completed the training for the visual-visual set with less errors. One other participant showed no differences between

Cross-Modal Equivalence Classes

the sets in terms of acquisition. Two of the four participants scored higher on the posttest for the visual-olfactory set of stimuli as compared to the visual-visual set, and one of these participants did not reach criterion for demonstrating equivalence on the visual-visual set during the initial training. These findings demonstrate a slight advantage for the in the acquisition of the visual-olfactory set of stimuli. These results are in accordance with past research done on cross-modal equivalence classes, which demonstrate higher performance on crossmodal equivalence class formation as compared to a single modal class (Green, 1990; Hayes, Tilley, & Hayes, 1988; Rehfeldt, & Dixon, 2005; Taylor & O’Reilly, 2000). The follow-up data demonstrate that two participants performed better on the visual-olfactory follow-ups, while one participant performed better on the visual-visual follow-ups. The fourth participant maintained both sets of stimuli at equal rates. This finding demonstrates that in general, the participants maintained equivalence relations for the visual-olfactory set of stimuli longer than the visual-visual set of stimuli, which supports past findings on maintenance of cross-modal equivalence classes (Rehfeldt, & Dixon, 2005). One possible reason for these findings is that the olfactory stimuli may have been more salient in their presentation, causing increased performance for this set of stimuli. A future study may wish to use much greater salient visual stimuli like pictures of cars crashing or nude models in an attempt to better control for this possible confound. By taking a conservative stance, the present data suggest that visual-olfactory classes are at least of similar utility as visual-visual classes in terms of acquisition and maintenance. However, olfactory stimuli in learning situations may have some advantages. Foods and many other stimuli are accompanied by smells. By taking a visual-olfactory approach to these stimuli we can incorporate both pictures and scents of stimuli to expose an individual to multiple dimensions of a stimulus, rather than only experiencing only a single aspect of a stimulus (e.g. visual representation). If we are teaching individuals the oral names and written names of foods we can incorporate both gustatory and olfactory senses into learning situations to build a larger class of relations. While some

97

stimuli have accompanying olfactory cues, some stimuli are purely olfactory to the learner. Gases are a good example of this kind of situation. Often you cannot see gas, but you can smell it. If teaching safety skills, incorporating the smell of gas (A stimulus) with actions such as calling the police (B stimulus) and leaving the house (C stimulus) will result in three stimuli that could be trained in a match-to-sample format with resulting derived relations between the B and C stimuli, so as to reduce the total amount of training. This safety skill can not be done with visual stimuli alone, making it irrelevant whether or not visual-olfactory learning is better than visually based learning. The results of the present experiment adds credence to this example of safety skills by adding that visual-olfactory classes have similar utility as visual-visual classes in terms of acquisition and maintenance. The current study was the first attempt to merge cross-modal and unimodal equivalence classes. While only one participant was able to meet criteria for demonstrating equivalence on the merger test, all participants consistently performed better as the test progressed, which supports past research on the delayed emergence of derived relations (Devany, Hayes, & Nelson, 1986; Sidman, Kirk, & Willson-Morris, 1985). During the sorting task however, all participants were able to meet criteria for demonstrating equivalence. Considerations for future research might look at the equivalence class formation that utilizes combinations of non-visual stimuli. To date, the cross-modal literature has looked at visual-gustatory classes of stimuli (Hayes, Tilley, & Hayes, 1988; Rehfeldt & Dixon, 2005), visual-auditory classes of stimuli (Green, 1990), and visual-tactile classes of stimuli (Bush, 1993), which have all been demonstrated as more efficient than using all visual stimuli. One might be led to believe that combining these stimuli (e.g., olfactory-gustatory classes of stimuli, auditory-tactile classes of stimuli, etc.) could result in quicker acquisition of relations and longer maintenance. Our study did have a number of potential limitations that should be considered when interpreting our results. First, due to the table-top nature of the stimulus presentations, inter-trial intervals

98

Daniel M. Fienup and Mark R. Dixon

were only loosely of equal length. At times it took the experimenter longer periods of time to arrange all stimuli for the initiation of the next trial. Second, the types of classes formed in this study were quite remedial. Formations of three member classes have been shown repeatedly in the published literature by verbally sophisticated humans. And finally, due to the rather exploratory nature of the use of olfactory stimuli, we did not control precisely for the saturation level of any liquid in the sock, thus potentially inadvertently making one stimulus more salient than another. Such limitations could easily be overcome in follow-up research. In summary, the present study has furthered out understanding of stimulus equivalence by exploring the formation and maintenance of visual-olfactory stimulus classes. Visual-olfactory class formation and maintenance is possible, and at similar levels when compared to a visual-visual stimulus class. By incorporating new modalities such as olfactory stimuli into research protocols, we gain a better understanding of the robustness of derived relational responding, and reduce the possibility of the inferences made being artifacts of characteristics of visual and/or auditory stimuli. References Annett, J. M. & Leslie, J. C. (1995). Stimulus equivalence classes involving olfactory stimuli. The Psychological Record, 45, 439-450. Bush, K. M. (1993). Stimulus equivalence and cross-modal transfer. The Psychological Record, 43, 567-584. Devany, J. M., Hayes, S. C., & Nelson, R. O. (1986). Equivalence class formation in language-able and language-disabled children.

Journal of the Experimental Analysis of Behavior, 46, 243-257. Green, G. (1990). Differences in development of visual and auditory-visual equivalence relation. American Journal of Mental Retardation, 95, 260-270. Hayes, L. J., Tilley, K. J., & Hayes, S. C. (1988). Extending equivalence class membership to gustatory stimuli. The Psychological Record, 38, 473-482. Rehfeldt, R. A., & Dixon, M. (2005). Evaluating the establishment and maintenance of visualvisual and visual-gustatory equivalence relations in adults with developmental disabilities. Behavior Modification, 29, 696-707. Rehfeldt, R. A., & Hayes, L. J. (2000). The long-term retention of generalized equivalence classes. Psychological Record, 50, 405-428. Sidman, M., Kirk, B., & Willson-Morris, M. (1985). Six-member stimulus classes generated by conditional-discrimination procedures. Journal of the Experimental Analysis of Behavior, 43, 21-42. Sidman, M., & Tailby, W. (1982). Conditional discrimination vs. matching to sample: An expansion of the testing paradigm. Journal of the Experimental Analysis of Behavior, 37, 5-22. Smeets, P. & Barnes-Holmes, D. (2005). Auditory-visual and visual-visual equivalence relations in children. The Psychological Record, 55, 483-503 Taylor, I. & O’Reilly, M. F. (2000). Generalization of supermarket shopping skills for individuals with mild intellectual disabilities using stimulus equivalence training. The Psychological Record, 50, 49-62.