JOURNAL OF APPLIED BEHAVIOR ANALYSIS
2015, 48, 1–5
NUMBER
1 (SPRING)
DO MIRRORS FACILITATE ACQUISITION OF MOTOR IMITATION IN CHILDREN DIAGNOSED WITH AUTISM? SCOTT A. MILLER, NICOLE M. RODRIGUEZ,
AND
AMI J. ROURKE
UNIVERSITY OF NEBRASKA MEDICAL CENTER’S MUNROE-MEYER INSTITUTE
We evaluated the efficacy of a procedure that incorporated a mirror to teach gross motor imitation with a 2-year-old boy who had been diagnosed with autistic disorder. Responses taught with a mirror were acquired more quickly than responses taught without the mirror and were maintained after the mirror was removed. These data indicate that a mirror can facilitate acquisition of motor imitation. Key words: autism, mirror, motor imitation, skill acquisition
The ability to imitate may serve as a behavioral cusp that leads to the learning of new repertoires (Rosales-Ruiz & Baer, 1997). For example, imitation may facilitate the development of social skills and language in children. Unfortunately, some children with autism do not acquire imitative skills without direct instruction (Rogers & Pennington, 1991). In such cases, the use of a mirror may promote imitation by providing visual feedback regarding the correspondence between the observed sample stimulus and the position of one’s own body (Catania, 1998, Chapter 13; Du & Greer, 2014), particularly when the correspondence between the modeled and imitative response cannot be easily observed (e.g., facial expressions and hand gestures that are not within the learner’s normal range of vision). Recently, researchers have begun to evaluate the effects of mirrors on imitative responding (i.e., Du & Greer, 2014). Du and Greer (2014) studied the effects of mirrors on imitative responses and generalized imitation relative to face-to-face (no-mirror) procedures in a between-groups comparison with six children (three per group) who had been diagnosed
with autism spectrum disorder (ASD). Children in the mirror condition correctly imitated and demonstrated more novel topographies than children in the no-mirror condition. Although the experimental design did not allow a direct comparison of the effects of mirror and nomirror methods, Du and Greer provided preliminary evidence of the potential benefits of incorporating mirrors to teach imitative responding to children with ASD. Imitative responses necessarily require the learner to orient toward the model rather than the topographical correspondence of their behavior with respect to the model. A mirror may be useful in that it allows this type of additional visual feedback, which may facilitate establishing the necessary discriminative control of the model. To date, only one study (Du & Greer, 2014) has evaluated the benefits of including a mirror on the acquisition of imitative behavior for children with ASD. The purpose of the current study was to evaluate the efficiency of teaching imitative responses using a mirror compared to responses trained in the absence of the mirror.
We thank Kevin C. Luczynski for his suggestions for data display. Address correspondence to Nicole M. Rodriguez, Munroe-Meyer Institute, University of Nebraska Medical Center, 985450 Nebraska Medical Center, Omaha, Nebraska 68198 (e-mail: [email protected]) doi: 10.1002/jaba.187
METHOD Participants, Setting, and Materials Bryce, a 2-year-old boy who had been diagnosed with ASD, had attended a university-based early intervention program for 1
2
SCOTT A. MILLER et al.
2 months before his participation in the study. Bryce was selected for participation because he did not engage in motor imitation despite multiple attempts to target this skill. All trials were conducted in a cubicle (2.4 m by 1.8 m) that contained a table, two chairs, reinforcers (e.g., edible items and toys), pen and data sheets, and a free-standing mirror (0.75 m by 1 m) positioned on the floor. The mirror was present only during sessions in which it was used for teaching. Design and Procedure Mirror-present and mirror-absent conditions were compared using an adapted alternating treatments design (Sindelar, Rosenberg, & Wilson, 1985) embedded within a concurrent multiple baseline across sets of responses. Four pairs of responses were assigned to either the mirror-present condition or mirror-absent condition and were evaluated across two sets. For Set 1, pairs were randomly assigned to the mirrorpresent and mirror-absent conditions. For Set 2, the pair associated with the highest level of responding during baseline was assigned to the mirror-absent condition to allow a more compelling demonstration of the effects of the mirror. Pair 1 included hands on cheeks and arms out to the side; Pair 2 included touch eye and raise arm; Pair 3 included touch nose and touch stomach; and Pair 4 included touch ear and touch shoulder. Target responses in each pair were quasirandomly distributed across a 10-trial session so that no target response was presented consecutively for more than two trials. To control for the visual feedback provided by the mirror, we selected response topographies that were not within the participant’s normal range of vision (e.g., touch ear). Across all conditions, reinforcers were selected from a one-trial multiple-stimulus-without-replacement preference assessment (similar to DeLeon & Iwata, 1996) that was conducted before each session. Baseline (differential reinforcement). The mirror was not present during baseline for either
condition. Bryce and the therapist sat in chairs facing each other. The therapist obtained eye contact and said “do this” while modeling the response. Prompts were not provided, and incorrect responses received no programmed consequence. Praise and edible reinforcement were delivered contingent on correct imitation. Interventions: Mirror present versus mirror absent. We used progressive prompt-delay (Charlop, Schreibman, & Thibodeau, 1985) and prompt-fading procedures during both mirrorpresent and mirror-absent conditions to transfer stimulus control from prompts to the discriminative stimuli (i.e., modeled response). For sessions with the mirror present, Bryce sat on the floor facing the mirror with the therapist positioned behind and to the right of him. The therapist obtained eye contact in the mirror before delivering the instruction. During the mirrorabsent condition, the therapist and Bryce were seated in chairs facing each other, and the therapist obtained eye contact before delivering the instruction. The mirror was added to Pair 2 after 28 sessions without an increase in correct responding. The prompting steps included (a) 0 s to full physical; (b) 2 s to full physical; (c) 0 s to partial physical, then 2 s to full physical if Bryce did not correctly complete the response; and (d) 2 s to full physical. A second therapist, positioned behind Bryce, provided all full and partial physical prompts during both conditions. The mirror was introduced at the 0 s to full physical prompt step for responses assigned to the mirror condition. We then introduced a 2-s delay to the full physical prompt to assess transfer of stimulus control after exposure to the 0-s prompting sessions. Because an increase in correct responding was not observed and errors consisted of incorrect responses rather than no responses, we introduced a 0 s to partial physical/2 s to full physical prompt as an intermediate step for transferring stimulus control from the physical prompt to the model while the potential for errors was reduced (Wolery & Gast, 1984). During the partial physical prompt, the therapist
MIRRORS AND MOTOR IMITATION placed two fingers under Bryce’s forearm and immediately guided the response halfway to completion (partial physical prompts were operationally defined per response to ensure consistency of implementation across sessions). The delay was increased to a 2-s delay to a full physical prompt after two consecutive sessions in which Bryce correctly completed the response on at least 90% of trials. As in baseline, praise and edible reinforcers were delivered contingent on correct responding across all sessions during both mirror-present and mirror-absent conditions. Mastery was defined as three consecutive sessions at or above 90% independent correct responding. Three to 5 days after responses taught with feedback from the mirror reached mastery, we conducted a probe session to evaluate whether correct responding would persist without feedback from the mirror. Response measurement, interobserver agreement, and procedural integrity. Observers collected data on Bryce’s correct, incorrect, and mirrororienting behavior. Correct responses were defined as imitating the model of the primary therapist within the specified prompt delay. Incorrect responses were defined as any motor movement other than the target behavior during the prompt delay. Mirror orienting was defined as Bryce making eye contact with the therapist through the mirror’s reflection. During the partial prompting procedure, a correct response was scored if Bryce independently completed the response after partial guidance. Data were converted to a percentage of trials with correct imitation for the purpose of data analysis. A second observer collected data during 42% of sessions. Interobserver agreement was calculated by dividing the number of agreements by the number of trials in a session (10) and converting the result to a percentage. An agreement was scored when each data collector recorded the same response during a trial. Mean agreement was 99% (range, 90% to 100%). The same observer simultaneously collected procedural integrity data on correct delivery of the
3
instruction, orientation of Bryce toward the therapist or therapist’s reflection in the mirror, and implementation of prompting and reinforcement contingencies. Each of these procedures needed to be implemented correctly for a trial to be recorded as correct. Integrity was assessed for 33% of all sessions and ranged from 93% to 100%, with a mean of 99.6%. RESULTS AND DISCUSSION Figure 1 shows the results of our evaluation. Correct responding was low during baseline across all sets, suggesting that differential reinforcement alone was insufficient to promote acquisition of the imitative response. Overall, when the intervention phase was introduced, correct responding increased more rapidly for pairs of responses in the mirror-present condition (28 sessions to mastery for Pairs 1 and 3) than in the mirror-absent condition (57 and 54 sessions to mastery for Pairs 2 and 4, respectively). Correct responding for Pair 2 remained low throughout the mirror-absent condition. After we introduced the mirror with Pair 2, responding reached mastery and remained high when the mirror was removed. The relative efficiency of teaching with feedback from the mirror was replicated for Set 2. Specifically, although mastery was eventually achieved in the mirror-absent condition (Pair 4), almost twice as many sessions were required than during the mirror-present condition (Pair 3). Thus, the current results provide evidence, in addition to previous work (e.g., Du & Greer, 2014), of the positive effects of mirrors on imitative responding in children with ASD. One limitation of this study is that, in contrast to patterns of responding for Pair 2, mastery levels were eventually observed for no-mirror responses in Pair 4. One plausible explanation is that generalized imitation (Du & Greer, 2014; Stokes & Baer, 1977) might have emerged as a result of multiple imitative responses having already been acquired in the mirror-present conditions (i.e., multiple-exemplar training). In
4
SCOTT A. MILLER et al.
Figure 1. Percentage correct imitation across Pair 1 (top panel), Pair 2 (second panel), Pair 3 (third panel), and Pair 4 (bottom panel) during baseline and intervention (mirror present vs. mirror absent).
this way, our results were consistent with those of Du and Greer (2014). It should be noted, however, that caution should be used with regard to conclusions that pertain to possible relations between the use of the mirror and generalized imitation given that (a) the effects were delayed and (b) we did not isolate this potential effect within the context of the experimental design. Differences in difficulty between mirror and nomirror responses, as might be suggested from the relatively higher levels of accurate responding during baseline, could have also contributed to the acquisition of Pair 4 without the mirror. As previously noted, the pair in Set 2 with the highest accuracy was assigned to the no-mirror condition to allow a more compelling demonstration of the effects of feedback from the
mirror. It is also worth noting that, like Pair 4, Pair 2 may have eventually been acquired with additional exposure to the teaching procedures in the absence of the mirror. Nevertheless, our results suggest that feedback from a mirror may be a more efficient means of teaching imitation, particularly for individuals in the early stages of developing a motor imitation repertoire. As previously noted, we selected responses that did not easily allow visual feedback without a mirror to control for the presence of visual feedback. Differential rates of acquisition under these conditions provide empirical support for Catania’s (1998) notion that a mirror may be beneficial in that it provides feedback between the modeled and imitative responses. However, it is unclear whether the mirror would have
MIRRORS AND MOTOR IMITATION provided any additional advantage had all of the target responses been within the child’s normal range of vision (e.g., hand or arm gestures that extended in front of the child). It is also unknown whether initially targeting movements that are within a child’s normal range of vision (e.g., clapping hands) would facilitate generalization of imitation across movements outside this range. Thus, future research should evaluate the effects of using mirrors to target movement within the normal range of vision. Future research should assess the generality of these findings by replicating this procedure across individuals with similar prerequisite skills and skill deficits. Future research might also evaluate the effects of differences in the position of the therapist in relation to the child (e.g., the therapist models responses in front of or next to the child during mirror or no-mirror conditions). The use of a mirror might also be useful in correcting inaccurate imitative responses such as when a child waves his or her hand with the palm facing him- or herself (e.g., during greetings). REFERENCES Catania, A. C. (1998). Learning (4th ed.). Englewood Cliffs, NJ: Prentice Hall. Charlop, M. H., Schreibman, L., & Thibodeau, M. G. (1985). Increasing spontaneous verbal responding in autistic children using a time delay procedure. Journal
5
of Applied Behavior Analysis, 18, 155–166. doi: 10.1901/jaba.1985.18-155 DeLeon, I. G., & Iwata, B. A. (1996). Evaluation of a multiple-stimulus presentation format for assessing reinforcer preferences. Journal of Applied Behavior Analysis, 29, 519–533. doi: 10.1901/jaba.1996. 29-519 Du, L., & Greer, R. D. (2014). Validation of adult generalized imitation topographies and the emergence of generalized imitation in young children with autism as a function of mirror training. The Psychological Record, 64, 161–177. doi: 10.1007/ s40732-014-0050-y Rogers, S. J., & Pennington, B. F. (1991). A theoretical approach to the deficits in infantile autism. Development and Psychopathology, 3, 137–162. doi: 10.1017/ S0954579400000043 Rosales-Ruiz, J., & Baer, D. M. (1997). Behavioral cusps: A developmental and pragmatic concept for behavior analysis. Journal of Applied Behavior Analysis, 30, 533–544. doi: 10.1901/jaba.1997.30-533 Sindelar, P. T., Rosenberg, M. S., & Wilson, R. J. (1985). An adapted alternating treatments design for instructional research. Education and Treatment of Children, 8, 67–76. Stokes, T. F., & Baer, D. M. (1977). An implicit technology of generalization. Journal of Applied Behavior Analysis, 10, 349–367. doi: 10.1901/jaba.1977.10-349 Wolery, M., & Gast, D. L. (1984). Effective and efficient procedures for the transfer of stimulus control. Topics in Early Childhood Special Education, 4, 52–77. doi: 10.1177/027112148400400305
Received February 19, 2014 Final acceptance August 24, 2014 Action Editor, Terry Falcomata
2015, 48, 1–5
NUMBER
1 (SPRING)
DO MIRRORS FACILITATE ACQUISITION OF MOTOR IMITATION IN CHILDREN DIAGNOSED WITH AUTISM? SCOTT A. MILLER, NICOLE M. RODRIGUEZ,
AND
AMI J. ROURKE
UNIVERSITY OF NEBRASKA MEDICAL CENTER’S MUNROE-MEYER INSTITUTE
We evaluated the efficacy of a procedure that incorporated a mirror to teach gross motor imitation with a 2-year-old boy who had been diagnosed with autistic disorder. Responses taught with a mirror were acquired more quickly than responses taught without the mirror and were maintained after the mirror was removed. These data indicate that a mirror can facilitate acquisition of motor imitation. Key words: autism, mirror, motor imitation, skill acquisition
The ability to imitate may serve as a behavioral cusp that leads to the learning of new repertoires (Rosales-Ruiz & Baer, 1997). For example, imitation may facilitate the development of social skills and language in children. Unfortunately, some children with autism do not acquire imitative skills without direct instruction (Rogers & Pennington, 1991). In such cases, the use of a mirror may promote imitation by providing visual feedback regarding the correspondence between the observed sample stimulus and the position of one’s own body (Catania, 1998, Chapter 13; Du & Greer, 2014), particularly when the correspondence between the modeled and imitative response cannot be easily observed (e.g., facial expressions and hand gestures that are not within the learner’s normal range of vision). Recently, researchers have begun to evaluate the effects of mirrors on imitative responding (i.e., Du & Greer, 2014). Du and Greer (2014) studied the effects of mirrors on imitative responses and generalized imitation relative to face-to-face (no-mirror) procedures in a between-groups comparison with six children (three per group) who had been diagnosed
with autism spectrum disorder (ASD). Children in the mirror condition correctly imitated and demonstrated more novel topographies than children in the no-mirror condition. Although the experimental design did not allow a direct comparison of the effects of mirror and nomirror methods, Du and Greer provided preliminary evidence of the potential benefits of incorporating mirrors to teach imitative responding to children with ASD. Imitative responses necessarily require the learner to orient toward the model rather than the topographical correspondence of their behavior with respect to the model. A mirror may be useful in that it allows this type of additional visual feedback, which may facilitate establishing the necessary discriminative control of the model. To date, only one study (Du & Greer, 2014) has evaluated the benefits of including a mirror on the acquisition of imitative behavior for children with ASD. The purpose of the current study was to evaluate the efficiency of teaching imitative responses using a mirror compared to responses trained in the absence of the mirror.
We thank Kevin C. Luczynski for his suggestions for data display. Address correspondence to Nicole M. Rodriguez, Munroe-Meyer Institute, University of Nebraska Medical Center, 985450 Nebraska Medical Center, Omaha, Nebraska 68198 (e-mail: [email protected]) doi: 10.1002/jaba.187
METHOD Participants, Setting, and Materials Bryce, a 2-year-old boy who had been diagnosed with ASD, had attended a university-based early intervention program for 1
2
SCOTT A. MILLER et al.
2 months before his participation in the study. Bryce was selected for participation because he did not engage in motor imitation despite multiple attempts to target this skill. All trials were conducted in a cubicle (2.4 m by 1.8 m) that contained a table, two chairs, reinforcers (e.g., edible items and toys), pen and data sheets, and a free-standing mirror (0.75 m by 1 m) positioned on the floor. The mirror was present only during sessions in which it was used for teaching. Design and Procedure Mirror-present and mirror-absent conditions were compared using an adapted alternating treatments design (Sindelar, Rosenberg, & Wilson, 1985) embedded within a concurrent multiple baseline across sets of responses. Four pairs of responses were assigned to either the mirror-present condition or mirror-absent condition and were evaluated across two sets. For Set 1, pairs were randomly assigned to the mirrorpresent and mirror-absent conditions. For Set 2, the pair associated with the highest level of responding during baseline was assigned to the mirror-absent condition to allow a more compelling demonstration of the effects of the mirror. Pair 1 included hands on cheeks and arms out to the side; Pair 2 included touch eye and raise arm; Pair 3 included touch nose and touch stomach; and Pair 4 included touch ear and touch shoulder. Target responses in each pair were quasirandomly distributed across a 10-trial session so that no target response was presented consecutively for more than two trials. To control for the visual feedback provided by the mirror, we selected response topographies that were not within the participant’s normal range of vision (e.g., touch ear). Across all conditions, reinforcers were selected from a one-trial multiple-stimulus-without-replacement preference assessment (similar to DeLeon & Iwata, 1996) that was conducted before each session. Baseline (differential reinforcement). The mirror was not present during baseline for either
condition. Bryce and the therapist sat in chairs facing each other. The therapist obtained eye contact and said “do this” while modeling the response. Prompts were not provided, and incorrect responses received no programmed consequence. Praise and edible reinforcement were delivered contingent on correct imitation. Interventions: Mirror present versus mirror absent. We used progressive prompt-delay (Charlop, Schreibman, & Thibodeau, 1985) and prompt-fading procedures during both mirrorpresent and mirror-absent conditions to transfer stimulus control from prompts to the discriminative stimuli (i.e., modeled response). For sessions with the mirror present, Bryce sat on the floor facing the mirror with the therapist positioned behind and to the right of him. The therapist obtained eye contact in the mirror before delivering the instruction. During the mirrorabsent condition, the therapist and Bryce were seated in chairs facing each other, and the therapist obtained eye contact before delivering the instruction. The mirror was added to Pair 2 after 28 sessions without an increase in correct responding. The prompting steps included (a) 0 s to full physical; (b) 2 s to full physical; (c) 0 s to partial physical, then 2 s to full physical if Bryce did not correctly complete the response; and (d) 2 s to full physical. A second therapist, positioned behind Bryce, provided all full and partial physical prompts during both conditions. The mirror was introduced at the 0 s to full physical prompt step for responses assigned to the mirror condition. We then introduced a 2-s delay to the full physical prompt to assess transfer of stimulus control after exposure to the 0-s prompting sessions. Because an increase in correct responding was not observed and errors consisted of incorrect responses rather than no responses, we introduced a 0 s to partial physical/2 s to full physical prompt as an intermediate step for transferring stimulus control from the physical prompt to the model while the potential for errors was reduced (Wolery & Gast, 1984). During the partial physical prompt, the therapist
MIRRORS AND MOTOR IMITATION placed two fingers under Bryce’s forearm and immediately guided the response halfway to completion (partial physical prompts were operationally defined per response to ensure consistency of implementation across sessions). The delay was increased to a 2-s delay to a full physical prompt after two consecutive sessions in which Bryce correctly completed the response on at least 90% of trials. As in baseline, praise and edible reinforcers were delivered contingent on correct responding across all sessions during both mirror-present and mirror-absent conditions. Mastery was defined as three consecutive sessions at or above 90% independent correct responding. Three to 5 days after responses taught with feedback from the mirror reached mastery, we conducted a probe session to evaluate whether correct responding would persist without feedback from the mirror. Response measurement, interobserver agreement, and procedural integrity. Observers collected data on Bryce’s correct, incorrect, and mirrororienting behavior. Correct responses were defined as imitating the model of the primary therapist within the specified prompt delay. Incorrect responses were defined as any motor movement other than the target behavior during the prompt delay. Mirror orienting was defined as Bryce making eye contact with the therapist through the mirror’s reflection. During the partial prompting procedure, a correct response was scored if Bryce independently completed the response after partial guidance. Data were converted to a percentage of trials with correct imitation for the purpose of data analysis. A second observer collected data during 42% of sessions. Interobserver agreement was calculated by dividing the number of agreements by the number of trials in a session (10) and converting the result to a percentage. An agreement was scored when each data collector recorded the same response during a trial. Mean agreement was 99% (range, 90% to 100%). The same observer simultaneously collected procedural integrity data on correct delivery of the
3
instruction, orientation of Bryce toward the therapist or therapist’s reflection in the mirror, and implementation of prompting and reinforcement contingencies. Each of these procedures needed to be implemented correctly for a trial to be recorded as correct. Integrity was assessed for 33% of all sessions and ranged from 93% to 100%, with a mean of 99.6%. RESULTS AND DISCUSSION Figure 1 shows the results of our evaluation. Correct responding was low during baseline across all sets, suggesting that differential reinforcement alone was insufficient to promote acquisition of the imitative response. Overall, when the intervention phase was introduced, correct responding increased more rapidly for pairs of responses in the mirror-present condition (28 sessions to mastery for Pairs 1 and 3) than in the mirror-absent condition (57 and 54 sessions to mastery for Pairs 2 and 4, respectively). Correct responding for Pair 2 remained low throughout the mirror-absent condition. After we introduced the mirror with Pair 2, responding reached mastery and remained high when the mirror was removed. The relative efficiency of teaching with feedback from the mirror was replicated for Set 2. Specifically, although mastery was eventually achieved in the mirror-absent condition (Pair 4), almost twice as many sessions were required than during the mirror-present condition (Pair 3). Thus, the current results provide evidence, in addition to previous work (e.g., Du & Greer, 2014), of the positive effects of mirrors on imitative responding in children with ASD. One limitation of this study is that, in contrast to patterns of responding for Pair 2, mastery levels were eventually observed for no-mirror responses in Pair 4. One plausible explanation is that generalized imitation (Du & Greer, 2014; Stokes & Baer, 1977) might have emerged as a result of multiple imitative responses having already been acquired in the mirror-present conditions (i.e., multiple-exemplar training). In
4
SCOTT A. MILLER et al.
Figure 1. Percentage correct imitation across Pair 1 (top panel), Pair 2 (second panel), Pair 3 (third panel), and Pair 4 (bottom panel) during baseline and intervention (mirror present vs. mirror absent).
this way, our results were consistent with those of Du and Greer (2014). It should be noted, however, that caution should be used with regard to conclusions that pertain to possible relations between the use of the mirror and generalized imitation given that (a) the effects were delayed and (b) we did not isolate this potential effect within the context of the experimental design. Differences in difficulty between mirror and nomirror responses, as might be suggested from the relatively higher levels of accurate responding during baseline, could have also contributed to the acquisition of Pair 4 without the mirror. As previously noted, the pair in Set 2 with the highest accuracy was assigned to the no-mirror condition to allow a more compelling demonstration of the effects of feedback from the
mirror. It is also worth noting that, like Pair 4, Pair 2 may have eventually been acquired with additional exposure to the teaching procedures in the absence of the mirror. Nevertheless, our results suggest that feedback from a mirror may be a more efficient means of teaching imitation, particularly for individuals in the early stages of developing a motor imitation repertoire. As previously noted, we selected responses that did not easily allow visual feedback without a mirror to control for the presence of visual feedback. Differential rates of acquisition under these conditions provide empirical support for Catania’s (1998) notion that a mirror may be beneficial in that it provides feedback between the modeled and imitative responses. However, it is unclear whether the mirror would have
MIRRORS AND MOTOR IMITATION provided any additional advantage had all of the target responses been within the child’s normal range of vision (e.g., hand or arm gestures that extended in front of the child). It is also unknown whether initially targeting movements that are within a child’s normal range of vision (e.g., clapping hands) would facilitate generalization of imitation across movements outside this range. Thus, future research should evaluate the effects of using mirrors to target movement within the normal range of vision. Future research should assess the generality of these findings by replicating this procedure across individuals with similar prerequisite skills and skill deficits. Future research might also evaluate the effects of differences in the position of the therapist in relation to the child (e.g., the therapist models responses in front of or next to the child during mirror or no-mirror conditions). The use of a mirror might also be useful in correcting inaccurate imitative responses such as when a child waves his or her hand with the palm facing him- or herself (e.g., during greetings). REFERENCES Catania, A. C. (1998). Learning (4th ed.). Englewood Cliffs, NJ: Prentice Hall. Charlop, M. H., Schreibman, L., & Thibodeau, M. G. (1985). Increasing spontaneous verbal responding in autistic children using a time delay procedure. Journal
5
of Applied Behavior Analysis, 18, 155–166. doi: 10.1901/jaba.1985.18-155 DeLeon, I. G., & Iwata, B. A. (1996). Evaluation of a multiple-stimulus presentation format for assessing reinforcer preferences. Journal of Applied Behavior Analysis, 29, 519–533. doi: 10.1901/jaba.1996. 29-519 Du, L., & Greer, R. D. (2014). Validation of adult generalized imitation topographies and the emergence of generalized imitation in young children with autism as a function of mirror training. The Psychological Record, 64, 161–177. doi: 10.1007/ s40732-014-0050-y Rogers, S. J., & Pennington, B. F. (1991). A theoretical approach to the deficits in infantile autism. Development and Psychopathology, 3, 137–162. doi: 10.1017/ S0954579400000043 Rosales-Ruiz, J., & Baer, D. M. (1997). Behavioral cusps: A developmental and pragmatic concept for behavior analysis. Journal of Applied Behavior Analysis, 30, 533–544. doi: 10.1901/jaba.1997.30-533 Sindelar, P. T., Rosenberg, M. S., & Wilson, R. J. (1985). An adapted alternating treatments design for instructional research. Education and Treatment of Children, 8, 67–76. Stokes, T. F., & Baer, D. M. (1977). An implicit technology of generalization. Journal of Applied Behavior Analysis, 10, 349–367. doi: 10.1901/jaba.1977.10-349 Wolery, M., & Gast, D. L. (1984). Effective and efficient procedures for the transfer of stimulus control. Topics in Early Childhood Special Education, 4, 52–77. doi: 10.1177/027112148400400305
Received February 19, 2014 Final acceptance August 24, 2014 Action Editor, Terry Falcomata
