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Mimetic relation as matching-to-sample observing response and the emergence of speaker relations in children with and without hearing impairments.

A number of studies have shown that stimulus equivalence represents an efficient way of teaching language to individuals with language delay and intellectual disabilities (i.e., Elias, Goyos, Saunders, & Saunders, 2008; Osborne & Gatch, 1989; Sidman, 1971; Sidman & Cresson, 1973). Stimulus equivalence is experimentally demonstrated when an individual, after being taught relations between members of three stimulus sets in one direction (i.e., select B in the presence of A, and C in the presence of B), will select A in the presence of B and B in the presence of C (symmetry) and C in the presence of A and A in the presence of C (transitivity) without further teaching and will also select any stimulus in the presence of its equal (i.e., A in the presence of A, B in the presence of B, etc.). As a practical example, after being reinforced for selecting the picture of a cat and the printed word cat, among other stimuli, upon hearing the spoken word /cat/, stimulus equivalence is demonstrated when the individual matches the printed word cat to the picture of a cat and vice-versa. This teaching can also yield saying /cat/ in the presence of both the picture of a cat and the printed word cat, although this latter emergent repertoire is not necessarily predicted to occur according to stimulus equivalence interpretations (Stromer, Mackay, & Stoddard, 1992).

Elias et al. (2008), for instance, used automated matching-to-sample tasks in a procedure aimed at teaching relations among nine digital video clips presenting manual signs and the corresponding pictures and printed words to seven adults with intellectual disabilities (four of whom were hearing impaired). Pretests were presented to identify signs the participants did not know. Then, they were taught relations among video clips (Set A) and pictures (Set B) and relations among printed words (Set C) and pictures (Set B) until a criterion of 100% of correct responses was reached. Next, they were tested for the emergence of the conditional relations AC, followed by tests of signing in the presence of the pictures (tact) and the printed words (textual); both test-type trials were not experimentally followed by any specific reinforcer. Both the observing response and the choice response on matching-to-sample (MTS) trials were touching the stimulus. A multiple-baseline design across three groups of three words was applied. Results showed the emergence of stimulus equivalence classes and also the emergence of correct signing in the presence of pictures or printed words for five of the seven participants.

One of the participants in Elias et al.'s (2008) study, the one with the best performance (fewer sessions to reach criterion during teaching and highest number of correct emergent signs) systematically and spontaneously imitated the signs presented as samples on the MTS tasks before choosing a comparison stimulus. Also, the other participants, who showed more errors and therefore required more trials to meet criterion during teaching and who showed fewer signs during testing, did not spontaneously sign in the presence of the sample stimuli. According to Horne and Erjavec (2007), not all individuals have a motor-imitative repertoire, and this skill may need to be directly taught. As to how spontaneous imitation can be brought about, at least theoretically, it is believed that signing in the presence of the sign would be introduced and maintained by the acquired reinforcer value of the correspondence between seeing and signing (Greer & Speckman, 2009).

Such bidirectional correlation observed in the Elias et al. (2008) results may indicate an already-established generalized imitation repertoire, meaning that this repertoire was transferred to the context of the MTS tasks and that the imitative response, controlled by a sign presented in a video clip, may have evoked the mimetic relation (Vargas, 1982). In the taxonomy of verbal behavior proposed by Skinner (1957), a gestural verbal response that has a point-to-point correspondence to an antecedent gestural verbal stimulus does not fit any of the verbal operant definitions. Such relation is a special instance of motor imitation, in which both antecedent and response are verbal. This special feature is encapsulated in the definition of a mimetic response as proposed by Vargas (1982).

After mimetic relations have been established in the context of the signed sample stimulus, response control may be transferred to the comparison stimuli. According to Lowenkron (1998, 2004), in MTS trials, a given verbal sample stimulus evokes a given verbal response (echoic, if vocal, or mimetic, if gestural) that is repeated (self-echoic or self-mimetic), and then this later response enters into joint control with only one of the comparison stimuli, the one that evokes the same verbal response topography being repeated. This verbal mediation is given by matching two distinct but topographically related verbal operants, typically an echoic or mimetic and a tact.

Teaching procedures derived of this interpretation, such as teaching individuals to imitate the signs prior to introducing MTS trials, may have powerful outcomes and allow participants to discriminate the signs successively, which is considered a prerequisite for the establishment of conditional discrimination relations (Saunders & Green, 1999).

Considering the potential for applications, the objective of this study was to investigate the effects of directly teaching mimetic responses (i.e., imitating a sign presented in a video clip) prior to introducing MTS trials and then using the mimetic as the differential observing response on an automated MTS procedure to establish stimulus classes containing video clips, pictures, and printed words and to generate the emergence of untaught signed tact and textual responses. The effects of the procedure were assessed using a multiple-baseline design across three groups of three words.



Participants were five 5-year-old Brazilian children. Participants Gra and Mat were profoundly deaf; Mat was deaf at birth, and Gra became deaf after having meningitis at the age of 12 months. Participants Eve, Will, and Yan had normal hearing. The deaf participants used general body and hand gestures to communicate, and Gra signed in the presence of the alphabet letters. In preexperimental tests, all participants performed at chance level in tests of relations between picture--printed word, and printed word--picture (relations BC and CB, respectively), and presented no correct responses in relations between printed word--sign (relation CA'). Also they reached 100% correct responses on identity matching-to-sample, first with pictures and then with printed words.

Gra and Mat were selected because they were the only deaf children in the classroom. The other children were selected because they were the oldest in the classroom. The children also showed willingness to participate. Before the onset, the participants' parents were given a brief description of the study to read, the opportunity to ask questions, and a consent form to sign, asserting their willingness to have their child participate. They were also informed that their children could withdraw from the study at any time.

Setting and Materials

The sessions were held in a room at the participants' school. A computer program (Elias & Goyos, 2010) presented stimuli and consequences, and recorded teaching and testing data as well as the participants' responses. Signing tests were recorded by a digital camcorder for interobserver agreement purposes. At the end of each workday, the participants could play a computer game for their participation, regardless of their performance. The number of sessions per day varied from two to five, depending on availability of time.

Experimental Stimuli

Three stimulus sets (A, B, and C), with nine corresponding stimuli each, were defined. Set A consisted of Brazilian Sign Language signs presented through video clips recorded as a QuickTime color movie, made especially for the purposes of this study. Only one trained model was used in the video clips. The model wore black, and the distance between the camera and the model was kept constant through all video recordings. Each video clip lasted about 10 s. Stimulus Set A video clips were always presented as sample in the MTS and mimetic tasks, on a 7.0 x 7.0 cm window. Set B consisted of the pictures that corresponded to the Set A video clips and were presented as 7.0 x 7.0 cm colored drawings. Set C consisted of corresponding printed words presented in uppercase Arial font, in bold, black, point size 30, typed against a white background (see Table 1). Words were chosen considering that six words should be formed by two syllables and three words by three or more syllables. Set A' consisted of the participants' signed responses.
Table 1
Set C Printed Words, Corresponding Set B Pictures, and
Pictorial Representation of Set A Video Clips

Printed  Pictures  Video    Printed Words  Pictures  Video Clip
Words              Clip
(Set C)  (Set B)   (Set A)  (Set C)        (Set B)   (Set A)
ENXADA                      MORANGO
FACA                        PATO
FOGO                        RATO
GALINHA                     RODA
GARRAAS                     SAPATO
GATO                        SOFA
JANELA                      VACA
MEIA                        VELA



During pretests, each AB, AC, BC, and CB relation was presented three times in separated 18-trial sessions. Each BA' and CA' relation was then presented once in two separate 18-trial sessions. The participant's lowest performance on the pretests was considered to select nine video clips and their corresponding pictures and printed words (see Table 2).
Table 2 Individually Selected C Stimulus Sets With
Portuguese Printed Words Presented for Each Participant
in Each of the Three Word Groups Stimulus Groups


Stimulus    Eve      Gra        Mat         Will       Yan

          FOGO     FACA     FOGO          FOGO     FACA

1         MEIA     FOGO     MEIA          GATO     FOGO

          PATO     RODA     RATO          MEIA     GATO

          RATO     MEIA     RODA          RODA     MEIA

2         RODA     SOFA     VACA          SOFA     RATO

          VACA     VELA     PATO          VELA     VELA




Imitation teaching. The first training phase consisted of teaching the participants to imitate each of the Group 1 signs--AA'. Each trial started with a Set A video clip stimulus presented in the upper center portion of the monitor (sample stimulus position) and the instruction to imitate the video clip. For Gra and Mat, signed instruction was presented; for Eve, Will, and Yan, vocal instruction was presented. In both cases, the instruction was "Do the same." Correct signed responses were followed by the experimenter clicking on the sample stimulus area of the computer screen and then again on a specific area of the computer screen, a computer animation with verbal praise, a 2 s intertrial interval, and the presentation of the next trial.

Incorrect signed responses--or any response, signed, oral, or otherwise--different from the required response after 5 s were followed by the experimenter providing verbal and nonverbal prompts. For the non-hearing-impaired children, the experimenter played the video clip again and orally provided the instruction, "Do the same." For the hearing impaired children, the experimenter pointed to the computer, played the video clip again, and signed the instruction "It is your turn. Do the same sign." If the participant still did not follow the instruction after an additional 5 s, the experimenter pointed to the computer, played the video clip again, imitated the video clip himself, and signed "It is your turn. Do the same sign." The hierarchy of instruction was provided again in a new trial only if the participant did not imitate the video clip after 5 s. Correct responses after prompting were followed by an oral or signed "OK" provided by the experimenter, the experimenter clicking on the sample stimulus area of the computer screen and then again on a specific area of the computer screen, a blank screen on the monitor, and the presentation of the next trial.

Three trial blocks of Al was successively presented until three consecutive correct Al' responses were performed without prompting. Next, A2 and A3 signs imitation were conducted with the same procedure. Finally, all three video clips were randomly presented three times each in a nine-trial block until a criterion of 100% of correct sign imitation was reached.

Matching-to-sample sessions. Following the mastery of imitation of Group 1 signs, MTS sessions were first introduced to teach relations AB for Group 1 stimuli. Each trial started with the single presentation of a Set A video clip as sample stimulus in the upper portion of the monitor and the instruction "Do the same" (auditory for the non-hearing impaired children, and gestural for the hearing impaired children), so that the observing response to the video clip was the mimetic relation. If the response was inaccurate, the experimenter played the video clip again. After the mimetic response and the end of the video clip, the experimenter clicked on the sample stimulus to produce the presentation of three comparison stimuli (three pictures--one correct and two incorrect comparisons--from the same stimulus group) below the sample position. Target responses were made by the participant pointing to one comparison. The experimenter then clicked on the pointed comparison before delivering the programmed consequences. Class-consistent choices to the correct comparison were followed by a computer animation and a verbal praise. Incorrect choices were followed only by a blank screen. All trials were followed by a 2-s intertrial interval and the presentation of the next trial. A session consisted of a 12-trial block with AB trial types randomly interspersed, providing that not more than two trials of the same type were presented successively or more than two successive trials with the correct comparison presented in the same position.

When a criterion of 100% of correct responses in a session or 90% in two consecutive sessions was reached, relations AC for Group 1 video clips and printed words were taught using procedure identical to AB teaching. Next, six trials of relations AB interspersed with six trials of relations AC, using procedure identical to AB teaching, were taught to criterion in the same session for Group 1. Then, a test session with AB and AC interspersed with BC and CB trials (three trials per relation) for the same group was introduced, with no programmed consequences for all trials. Target responses in testing sessions were followed by a 2-s intertrial interval and the presentation of the next trial. Mimetic responses were required for relations AB and AC during test trials. The observing response on BC and CB test trials was only the pointing response.

Tact and textual sessions. After meeting 100% of correct responses on the mixed AB/AC/BC/CB test session, relations BA' and CA' were tested for all stimuli. Each trial started with the presentation of a picture or a printed word in the sample stimulus position and the instruction "Do the sign for this picture (or printed word)," vocally for the non--hearing impaired children and signed for the hearing impaired children. A response was recorded as correct if it matched its corresponding Set A stimulus and presented within 10 s from the stimulus onset. If the correct signed response was not presented within 10 s, or a different response was shown, an incorrect response was recorded. Correct and incorrect responses were followed only by a 2-s intertrial interval and the presentation of the next trial. Each session had 18 trials; one block of nine trials with different pictures was followed by one block of nine trials with different printed words. Within each block, the trials were presented randomly. Teaching and testing sessions were then introduced for the remaining groups of stimuli.

Experimental design. A multiple-baseline design across three groups of stimuli controlled for the effects of the independent variables (AB and AC teaching, and the emergence of derived relations BC and CB) on the dependent variable (correct responses on emergent relations BA' and CA').

Interobserver agreement. During signing tests for relations BA' and CA', each sign was analyzed as correct or incorrect by an independent observer. Agreement between experimenter and the independent observer's recordings was 100%, based upon a comparison of trial-by-trial analysis.

Treatment integrity. All trials in all experimental phases were presented by a computer program; therefore, no assessment was made.

Results and Discussion

Performance during pretests of relations AB, AC, BC, and CB is shown in Table 3. No errors were presented during sign-imitation teaching. After showing mastery of sign imitation, and after mastering AB and AC relations, participants met criterion and showed 100% of correct responses on the emergent relations BC and CB. Exceptions were found for Eve (Group 1; 33% incorrect responses for both BC and CB), Gra (Group 2; 33% incorrect responses only for BC), and Will (Group 3; 67% incorrect responses for both BC and CB). After presenting one session of mixed AB/AC teaching relations, all three participants reached criterion on relations BC/CB tests.
Table 3 Pretest Accuracy Score (Percentage Correct)

Relations     Eve  Gra  Mat  Will  Yan
AB             52   81   39    37   54
AC             24   35   40    24   25
BC             44   39   41    43   30
CB             44   33   34    33   32

Learning relations AB (video clip--picture) to criterion required fewer trials than for relation AC (video clip--printed word) for all stimulus groups and all participants (see Table 4), in spite of AC relations being the second conditional discrimination relations taught (Saunders & Spradlin, 1993).
Table 4 Number of Trials to Reach Criterion

                  Group      Group      Group
                  1          2          3

Participants  AB   AC    AB   AC    AB  AC
Eve           12   48    12   84    12  36
Gra           12  132    12  144    12  72
Mat           24   72    12  132    12  84
Will          24   84    12   60    24  36
Yan           12  156    12   48    24  36

An additional modified matching-to-sample task presentation format (Saunders & Spradlin, 1989) was introduced for AC relations in an attempt to promote comparison discrimination and gradually introduce reversal of comparison discrimination. Sessions consisted of 12 trials, with Al being presented four times consecutively, followed by four consecutive A2 trials, and four consecutive A3 trials, with Cl, C2, and C3 comparison stimuli in different positions across trials. Criterion to move over to the next phase allowed errors on only the very first trial after the sample stimulus was changed. In the next phase, the number of blocks increased from three to six, halving the number of trials in each block accordingly until 100% correct responses was reached, which was followed by the presentation of the original session with randomly presented trials. The same modified procedure was introduced, if required, to Groups 2 and 3 of words.

All participants showed the emergence of most signs when prompted by the presence of the pictures and printed words (see Figure 1). In general, the total number of correct BA' tact responses was considerably higher than correct CA' textual responses (dark and white bars on Figure 1, respectively), not only in immediate tests but also in maintenance tests. As compared with immediate tests, maintenance tests showed a gradual decrement in both tact and textual performance, with a slightly higher decrement for the textual performance. Different emergent performances in textual and tact relations have also been found in other studies (i.e., Elias et al., 2008; Osborne & Gatch, 1989; Sidman & Cresson, 1973, among others).


What is challenging about these results is how to account for the difference in performances in BA' and CA' once response topographies in both operants are similar, if not identical--implying that response cost is at least comparable, the evocative stimuli (picture or printed word) belong to the same experimentally established equivalence classes, and both BA' and CA' relations were not experimentally followed by any specific reinforcer. Maybe it is because being positive in the equivalence tests does not necessarily mean the stimuli are equivalent in all other different conditions, or maybe stimuli in an equivalence class are not equally related to each other (Fields & Moss, 2007). One possibility is that if the reinforcer enters the equivalence class, as suggested by Sidman (2000), and considering also that the two relations clearly have different histories--as indicated by the well-known fact that children learn tact relations earlier than textual relations--implying that several equivalence stimulus classes with pictures, objects and their names are probably well established outside the experimental context before expanding these classes to include letters, printed words, and their names. As an additional result, tact and textual relations may have acquired two or more different reinforcing values. How to control for these variables is an experimental objective well worth pursuing. Tsai and Greer (2006) suggested that, for orally capable children, reinforcement control for observing pictures may have been present, whereas reinforcement control for observing printed words was absent. For their important theoretical and practical implications, the differences between tact and textual performances still need to be accounted for (Guimaraes, 2012).

A major feature of this study seems to have been the mimetic teaching of a new manual sign coupled with the MTS task. This feature was gradually introduced. First, outside the MTS context, but still in the context of a computer task, the participants learned to successively discriminate among the video clips, an important prerequisite discrimination for matching-to-sample performance or the formation of stimulus classes. Then, this feature was brought in under the contextual control of an MTS task, during the AB and the AC teaching phases, because it was experimentally required. It may be important to have this repertoire directly trained, as pointed out by Young, Krantz, McClannahan, and Poulson (1994, p. 686), because "generalized imitation may be restricted to the type of responses for which imitative behavior has been reinforced and not to all responses modeled by the experimenter."

If signing did occur or to which extent it occurred during BC and CB trials is still unclear. Unsystematic observations indicated some signing on some BC and CB trials at the onset of the sample stimulus presentation. Such responses were never followed by any specific experimentally defined consequences but the instruction to touch the sample stimulus.

It is possible that during these experimental phases the participant was simultaneously learning speaker-and-listener relations to those particular manual signs, which adds to the other known economical features of the MTS general teaching procedure. These relations may have benefitted from previously learned naming relations (Horne & Lowe, 1996) regarding different response topographies for hearing and non-hearing participants. Emergent speaker behavior (BA' and CA') may thus have been a function of all previous relations combined.

Mimetic teaching may also be fundamental to teach relations in which the first stimulus is a compound stimulus (a sequence of frames) and can replace the standard pointing or touching observing response with advantages. For videos, such as in the current study, touching or pointing does not ensure the observation of all stimulus features, consisting of a dynamic and variable sequence of frames. Mimetic responding as a mediating response on MTS trials may be an important component in the emergence of new signing relations (Horne & Lowe, 1996; Lowenkron, 1998). However, this feature needs further investigation by, for example, comparing the results from this procedure with one that does not include the mimetic responding during teaching phases.

The successful establishment of stimulus classes including video clips along with pictures and printed words may be an important step for future studies to investigate the use of videos to teach sequelic relations (Vargas, 1982) as in sentence construction and grammar. The participant may tact the event in a video, such as subject, verb, and complements, which may serve as a prompt for written, oral, or signed sentence construction.


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We acknowledge Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) for general continued support and for postdoctoral scholarship to the first author (process # 2008/04407-0), and Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) research scholarship to the second author (process # 307771/2007). The authors are grateful to Daniela M. Ribeiro and Thomas S. Higbee for comments, criticisms, and suggestions on previous versions of this manuscript.

Correspondence concerning this article should be addressed to Celso Goyos, Universidade Federal de sao Carlos, Rodovia Washington Luis, km 235-SP-310, sao Carlos, SP, Brasil, CEP 13565-905. E-mail:

Nassim Charnel Elias and Celso Goyos

Universidade Federal de Silo Carlos, Brazil
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Author:Elias, Nassim Chamel; Goyos, Celso
Publication:The Psychological Record
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Geographic Code:3BRAZ
Date:Jan 1, 2013
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