John Demanche & James T. Chok

Transcription

1 The Use of Wrist Weights and Vibratory Stimulation to Treat Self-Injurious Behavior John Demanche & James T. Chok Journal of Developmental and Physical Disabilities ISSN X DOI /s

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3 DOI /s ORIGINAL ARTICLE The Use of Wrist Weights and Vibratory Stimulation to Treat Self-Injurious Behavior John Demanche & James T. Chok # Springer Science+Business Media New York 2012 Abstract Identifying successful interventions for persistent and frequent selfinjurious behavior maintained by automatic reinforcement can be very challenging. Two treatments that have shown some promise in isolation have been the use of wrist weights, and vibratory stimulation as an alternative means to achieve sensory reinforcement. The current study examined the effects of these interventions separately, and in combination, to address chronic self-injurious behavior in a child with autism and intellectual disability. Although wrist weights resulted in substantial decreases in self-injurious behavior, the combination of wrist weights and vibratory stimulation matching the hypothesized sensory consequences of self-injurious behavior resulted in further decreases. The use of vibratory stimulation that did not match the hypothesized sensory consequences of SIB was not effective at reducing SIB when it was presented alone or in combination with wrist weights. Keywords Wrist weights. Matched and unmatched vibratory stimulation. Self-injurious behavior. Automatic reinforcement The treatment of high frequency self-injurious behavior (SIB) that is maintained by automatic reinforcement can be very challenging. If procedures emphasizing positive reinforcement have been ineffective at mitigating SIB, more restrictive procedures are often employed, such as the use of protective equipment to enact sensory extinction, and/or punishment (e.g., response blocking). The use of wrist weights has been shown to be an effective antecedent manipulation for reducing high rates of SIB. It is thought that the use of weights increases response effort for SIB, or alters the quality of reinforcement by decreasing the J. Demanche : J. T. Chok (*) Melmark New England, 461 River Rd, Andover, MA 01810, USA jchok@melmarkne.org

4 force of impact (Hanley et al. 1998). Van Houten (1993) was able to show that the use of 0.68 kg (1.5 lb) weights applied to each wrist for 1 h each day resulted in low to zero rates of face-slapping both during their application and 5 min pre- and postweight sessions. Van Houten also indicated that the weights were contingently applied for 30 min (up to twice a day) following a face slap for 3 weeks following the study, and self-injury was not evident during a 5 month follow-up in which data was collected for 30 min for five consecutive days. Van Houten (personal communication) reported that the client s face-slapping behavior did not return over a 5 year period. Hanley et al. (1998) demonstrated that the use of 0.92 kg (2 lb) weights applied to each wrist also led to low to zero levels of SIB during 5 min sessions. The extant literature, however, does not include instances of successfully fading weights to lower values than those just reported, or demonstrating their effects across extended observation periods. Another antecedent intervention used to decrease SIB is vibratory stimulation. Presumably, if SIB is subserved by a sensory function, it may be possible to provide equivalent sensory experiences that require less response effort to achieve. If this could be accomplished, accessing alternative, safer forms of sensory stimulation would be more efficient than engaging in SIB. If provided on a rich schedule of reinforcement, these alternative sensory experiences should lead to satiation, and in turn, render SIB irrelevant as well (Sandler 2001). Bailey and Meyerson (1970) were able to reduce SIB to near-zero levels for a child with profound intellectual disability by allowing noncontingent access to vibration. Wells and Smith (1983) demonstrated that providing vibratory stimulation to the areas of the body impacted by SIB (i.e. stimulation that matched the hypothesized sensory consequences of SIB) resulted in significant decreases in SIB for all four subjects in their study. Access to vibratory stimuli upon the removal of protective equipment has also been shown to significantly reduce SIB for brief time periods (O Reilly et al. 2003). Lastly, Van Houten (1993), during additional functional analysis sessions, evaluated whether vibration might be a possible sensory consequence of face slapping. He reported that, during 5 min sessions, face slapping averaged 3.7 responses per minute in the absence of vibration, and 0.0 responses per minute in the presence of vibration. Although wrist weights and vibratory stimulation have been used separately to treat SIB, there have been no studies to date combining these interventions. This is of particular interest because, for at least some individuals, this type of treatment package may result in greater decreases in SIB than either treatment used in isolation. Moreover, fading wrist weights to lower values would provide the client with a less restrictive procedure. The long-term effects of wrist weights on physical health has not yet been studied, but one would surmise that if heavier weights are worn for long periods of time each day over the course of years, there may be some deleterious impact on the individual s joints or physical development. The current study examined the effectiveness of wrist weights and vibratory stimulation, both in isolation and in combination, for decreasing the SIB of a child with autism and intellectual disability. In addition, the impact of vibratory stimulation on the rate of SIB was evaluated when its sensory consequences either matched the hypothesized sensory consequences of SIB, or provided unmatched sensory consequences.

5 Method Participant and Setting Taylor, a 12 year-old boy with autism and moderate intellectual disability, had a prolonged history of frequent and intense SIB. Despite receiving intensive 1:1, yearround services at a school specializing in the delivery of applied behavior analysis, Taylor s rates of SIB had remained relatively stable over the four years since his enrollment. Taylor s SIB occurred throughout the day at a high frequency, and resulted in significant tissue damage, including swelling, bruising, and lacerations. On one occasion, he required emergency care for a hematoma that developed on an area of his head that was typically targeted during SIB. Taylor s primary topography of SIB was hitting the side of his head and the cheekbone area of his face with the base of his palm, and he usually did this silently. Previous clinicians working with Taylor had attempted to reduce his SIB through the use of a helmet and, at times, major changes to his environment (such as removing all demands for a week). In addition, multiple reinforcement procedures had been attempted with little to no success. One of these programs, a differential reinforcement of other behavior procedure, provided Taylor with a variety of reinforcers contingent upon the absence of SIB for a specified duration (e.g., work tasks were shorter, breaks where Taylor could access preferred tangibles and activities were lengthened, and physical attention was given if requested). However, his rates of SIB remained high, sometimes reaching over 1,000 instances of self-injury in a day, despite intensive clinical programming. During previous extended alone conditions, Taylor, while wearing a helmet, was observed to methodically hit himself in the head at a near continuous rate while remaining in his seat, staring at the floor. These observations suggested Taylor s SIB was maintained by automatic reinforcement. At the beginning of the current study, a brief functional analysis without the use of a helmet was conducted using conditions similar to those incorporated by Iwata et al. (1982/ 1994). The results also indicated that Taylor s SIB was maintained by automatic reinforcement as evidenced by high rates of SIB across conditions. Taylor s rates of SIB per minute were highest in the Play (X062.5) and Alone (X058.5) conditions. His SIB quickly intensified during all sessions and similar to previous observations, he stared at the floor during his self-injury. Dependent Variable and Measurement SIB was defined as anytime Taylor made hand-to-head contact, excluding incidental contact such as scratching his scalp and rubbing his eyes (which never resulted in tissue damage and was not observed to occur at high rates). Each hand could produce an instance of SIB. Therefore, if Taylor hit his head with his left and right hands at the same time, this was counted as two instances of SIB. The frequency of SIB was collected across each school day, which constituted a single session and ranged from 5 to 6 h each day. If Taylor attended school for less than 5 h, the data from that day was excluded from analyses (this occurred on five occasions). The total SIB for a given session was divided by the number of hours data was collected for that particular day, to yield a measure of SIB per hour. Approximately midway through

6 the study, we discussed the value of not only reducing Taylor s SIB, but also reducing his attempts as well. We believed that if we could demonstrate that the interventions we applied reduced both SIB and attempts to engage in SIB, the treatment effects would be more convincing. In addition, if Taylor s SIB, including attempts, could be reduced to zero or near-zero rates, this might confer a greater level of independence in that he might not require a teacher to remain nearby at all times. Therefore, starting with session 121, we included SIB attempts in our operational definition. We considered an attempt to have occurred any time Taylor went to strike his head with his hand, but did not make contact. Interobserver Agreement An independent observer recorded SIB during 80 of the 286 (28 %) of sessions during min samples per session. The total amount of time in which data were collected by a secondary observer was 72 h, which was 4 % of the total amount of time in which data were collected (1,688 h). Data were organized into 30 min bins and each bin was considered an interval. The percent agreement for each bin was computed by dividing the smaller number observed by the larger number. Percent agreement for each bin was added together and divided by the total number of bins (144 total bins). Mean count per interval IOA for SIB was 97.8 % (range %). The single instance of 0 % IOA occurred during a bin in which one observer recorded one instance of SIB and the second observer recorded zero SIB. Preference Assessments Two preference assessments were conducted during this project to evaluate Taylor s preference for vibratory stimulation. The first preference assessment occurred at the start of the study and involved one item, a Mini ISmart Massager ( sager.com, $159.99). The unit was notable for its small, lightweight size, and its similarity to popular mini MP3 players. It easily affixes to one s arm and the wires to the electrodes can be run underneath clothing. The massager delivers varying levels of intensity in one unit increments up to a level of ten. Prior to conducting a preference assessment with Taylor, the co-authors of this paper, along with an independent senior clinician at our agency, tested out the massage unit on various parts of the body. We initially planned to place the electrodes on Taylor in the cheek bone area of his face or the base of his palm, two of the main areas stimulated when he engaged in SIB (the side of the head was not included as a potential placement site because the electrodes could not attach to the skin given the student s hair). However, all three clinicians found the stimulation of the facial area to be very painful and cause undesirable muscle contractions (e.g., eyelid muscles), even on low settings. All three clinicians found the palm area of the hand to be mildly uncomfortable, even at lower settings. Given that these two areas contain bony structures, other areas of the body were stimulated. All three clinicians reported that thicker, muscular areas of the body, such as the back muscles between the shoulder blades, delivered the most pleasant experience. Following this assessment, the facial area was ruled out as a possible location and a preference assessment was conducted with Taylor using his palm and the upper middle portion of his back.

7 After placing the electrodes on Taylor, the unit was started at an intensity level of one and vibratory input was provided for 1 min. After each minute, Taylor was asked, Do you want more? If he responded with sign language for More, he was given a gesture prompt to press the start button on the unit and the trial was scored +. If Taylor did not respond within 5 s, responded with sign language for All done, or attempted to take off the electrodes, the trial was scored -. Ten trials were administered at each level and the highest level in which Taylor indicated he wanted more stimulation during 100 % of the trials was chosen as the level of input for intervention. The results of this preference assessment indicated that Taylor did not prefer stimulation on the wrist area (he took the electrodes off prior to a minute expiring for each of the first three trials). When the electrodes were placed on Taylor s back, the highest level of intensity he selected was five. By the end of the preference assessment, Taylor was able to independently turn the massager on and off. Following an initial treatment evaluation of this massager, an additional preference assessment was conducted. It was hypothesized that perhaps one of the reasons vibratory stimulation of the initial massager did not result in lower rates of SIB was because the sensory consequences did not match the sensory consequences believed to occur following SIB. The second preference assessment, therefore, involved an evaluation with five items that could produce sensory consequences that matched the consequences thought to be maintaining SIB. The ISmart Mini Massager was included for comparison purposes, making for a total of six items in this assessment. The procedures employed were similar to those described by Piazza et al. (2000). However, rather than presenting one item at a time, a multiple stimulus without replacement assessment (MSWO) was conducted. Once an item was selected, it was activated and presented to Taylor for 3 min. Matched stimulation, non-matched stimulation, and SIB were coded using a 10-s partial interval recording system. No consequences for SIB were provided. Matched stimulation was defined as using the item in a manner that resulted in contact with any area of Taylor s head or palm (a + was scored if it did, a - if it did not), whereas non-matched stimulation was defined as using the item in a manner that resulted in contact with any area of the body other than Taylor s head or palm (a + was scored if it did, a - if it did not). Three MSWO sessions were conducted on three separate days. Results from this assessment indicated that the most preferred item was an OSIM ucrown 2 Head Massager ( stone.com, $199.99), which alternates between providing tension in a band that wrapped around the head and vibration. Use of this item also resulted in the greatest amount of access to matched stimulation (three session average of 83.3 % of intervals) in comparison to the other items, and low rates of SIB (three session average of 9.3 % of intervals). All instances of SIB when accessing this item occurred when Taylor was not wearing the unit. No other items were accessed in a manner that produced large amounts of matched stimulation (the next highest item average was a percussion style massager at 29.6 % of intervals). The item that produced the greatest amount of unmatched stimulation was the ISmart Mini Massager (96.3 % of intervals). It was also associated with low rates of SIB (three session average of 3.7 % of intervals), but was one of the least preferred items in the assessment.

8 Experimental Design and Procedure The effects of wrist weights and vibratory stimulation on the rate of SIB, either in isolation or in combination, were evaluated using a multiple treatments reversal design. Vibratory stimulation either matched the hypothesized sensory consequences of SIB (OSIM ucrown 2 Head Massager) or provided unmatched sensory consequences (Mini ISmart Massager). Baseline Given the frequency and intensity of Taylor s SIB at the start of this study, baseline sessions were not devoid of treatment for the sake of Taylor s safety. Upon any attempt to engage in SIB, the teacher working with him blocked the attempt, maintained neutral affect, and continued with the task at hand. Blocking of SIB also occurred in each of the various treatment conditions which are described below. Given the intensity and rapidity of Taylor s SIB, Taylor was able to engage in high rates of this behavior even when his teachers responded quickly. Once the teacher began blocking, Taylor continued to attempt to hit himself, twisting and turning his body away from his teacher and becoming aggressive as well. Given the vigor with which Taylor engaged in SIB and his resistance to the blocking procedure, he was still able to accumulate a high frequency of SIB with this treatment strategy in place. Wrist Weights Treatment began by placing a 1.81 kg (4 lb) hard weight (Leadex Group, $12.00) housed in Velcro straps on each of Taylor s wrists. During the course of the study, the weights were reduced to 0.91 kg (2 lb), 0.68 kg (1.5 lb), 0.45 kg (1 lb), 0.23 kg (0.5 lb), and 0.11 kg (0.25 lb) increments. If an escalating trend was observed at a given weight, a heavier weight was reintroduced. If Taylor s rate of SIB remained stable or declined, a lower weight was introduced. The 1.81 kg (4 lb) wrist weights were observed to interfere with some of Taylor s adaptive skills and were removed during lunch time. Given this undesirable side effect, no weight greater than 1.81 kg (4 lb) was used in this study. Although adaptive skills were not formally measured, observations by both authors of Taylor engaging in various adaptive activities, interviews with his teachers, and a review of his performance on academic tasks indicated that the 0.91 kg (2 lb) wrist weights and lower value weights did not interfere with Taylor s ability to perform adaptive skills. Unmatched Vibratory Stimulation During this condition, the leads from the Mini ISmart Massager were placed on Taylor s back and the unit was activated at the level determined during the preference assessment. After 1 min of access, the massager was turned off. Taylor was permitted to independently turn the massager back on, but if he did not, the unit remained off until Taylor turned it back on himself or a prompted trial occurred. Prompted trials were conducted at the start of each hour of the school day (e.g., 10 am, 11 am, 12 pm, etc.) if Taylor was not accessing the massager at time. During prompted trials Taylor was reminded, Remember, you can turn on your massager, and the teacher activated it for him. Matched Vibratory Stimulation During this condition, Taylor was provided access to the OSIM ucrown 2 Head Massager contingent upon a functional communication response which was established in the lead author s office during a two-week prior to

9 the massager being available in the classroom. Functional communication training (FCT) sessions occurred once per day and consisted of ten trials using errorless teaching (most-to-least prompting). During training sessions, the massager was set approximately 1 m away from Taylor during each trial. A green card with a picture of the massager on it was affixed (using Velcro ) to the cover of a small three-ring binder with a shoulder strap that Taylor could use to carry the card to and from the classroom. Contingent upon Taylor handing over the green card, the massager was placed on his head and activated for 1 min. Once Taylor independently exchanged the card 10 out of 10 trials for three consecutive sessions, the unit was brought to the classroom for an additional training session in that setting. Taylor demonstrated the ability to request the item during the first session (he independently requested it using the card 10 out of 10 trials), and thus the next day, treatment using matched vibratory stimulation began. During treatment, the massager remained within 3 ft of Taylor at all times. After exchanging the green card, Taylor was provided 1 min of access to the massager. After 1 min, the unit was removed from his head and remained off until Taylor requested it again, or until a prompted trial was conducted (in the same manner as described in the unmatched sensory consequences section). If Taylor engaged in SIB while accessing the massager, or attempted to engage in SIB, the green card was removed from the binder cover and replaced with an equivalent size red card. When the red card was present, any requests for the massager using the red card were ignored (the green card was in the teacher s possession when removed, out of Taylor s view). After Taylor was absent of SIB for 1 min, the red card was removed from Taylor s sight, the green card was placed back on his binder cover, and requests for the massager using the green card were granted. Results Taylor s rate of SIB across conditions is displayed in Fig. 1 (a closer view of sessions can be seen in Fig. 2, which also includes SIB attempts). The data collected during the lunchtime weights-off period are not depicted in either figure. As can be seen in Fig. 1, Taylor s average rate of SIB across the initial ten baseline sessions was high, at 83.5 per hour. When 1.81 kg (4 lb) weights were added to each arm, his rate of SIB dropped substantially to an average of 1.7 per hour (16.7 per hour during the 30 min lunchtime weights-off period). During a no-weights reversal condition, Taylor s rate of SIB spiked up to an average of 86.5 per hour (this condition was only kept in place for 2 days given the disparity of the treatment effect and in consideration of Taylor s safety). When 1.81 kg (4 lb) weights were put back in place, Taylor s average rate of SIB dropped significantly again to 7.1 per hour, resulting in a replication of the treatment effect. During the lunchtime weights-off period of this phase, Taylor s average rate of SIB was 50.5 per hour. An attempt was then made to fade the weights. Initially, the weights were halved to 0.91 kg (2 lb) per arm. Taylor s average rate of SIB remained low despite this decrease in weight (3.3 per hour). Therefore, the weights were halved again to 0.45 kg (1 lb) per arm. During the seven sessions comprising this condition, Taylor s average rate of SIB continued to remain low at 7.9 per hour.

10 160 BL 4 lb 2 lb 4 lb 1 lb 1 lb + UVS 2 lb 1.5 lb 1 lb 0.5 lb 0.25 lb 0.5 lb 0.5 lb + MVS 0.5 lb Velcro Straps RESPONSES PER HOUR Velcro Straps + MVS 0.5 lb + MVS BL BL UVS Only 0.25 lb SESSIONS Fig. 1 Rate of self-injurious behavior across all phases and sessions. The data depicted for sessions include attempts in the operational definition for SIB. BL 0 Baseline; UVS 0 Unmatched vibratory stimulation; MVS 0 Matched vibratory stimulation At this time, unmatched vibratory stimulation was introduced in addition to the 0.45 kg (1 lb) weights, with the hope that Taylor s SIB might be eliminated completely with both interventions in place. During this phase, Taylor s average rate of SIB was similar (9.1 per hour) to the previous weights only condition. Given that Taylor s rate of SIB was largely the same during these two conditions, we wondered if the massager by itself might be as equally effective as the wrist weights in reducing SIB. Therefore, a brief return to baseline was performed (Taylor s rate of responding spiked to 36.3 SIB per hour), followed by an access to unmatched vibratory stimulation session. Given that Taylor s rate of SIB remained high (39.0 per hour) and was at a level much higher than the highest data point observed during any of the previous phases with weights, this phase was discontinued and an attempt was made to fade Taylor s weights in a more gradual manner. During this component of the study, Taylor s weights were reduced from 0.91 kg (2 lb) to 0.23 kg (0.5 lb) by half pound increments. During each of these phases Taylor s rate of SIB remained low and stable. As a result, the weights were faded to 0.11 kg (0.25 lb). However, as can be seen in Fig. 2, following a period of low and stable responding, Taylor s rate of SIB began to sharply increase. Therefore, the 0.23 kg (0.5 lb) weights were reintroduced. Taylor s rate of SIB decreased again to a level consistent with the level of responding observed in the previous 0.23 kg (0.5 lb) phase. However, Taylor had yet to complete a session without engaging in SIB, and thus, there was still the possibility that further clinical gains could be made. In the

11 50 0.5lb 0.25lb 0.5lb 0.5lb + MVS 0.5lb 0.25lb Velcro Straps RESPONSES PER HOUR Velcro Straps + MVS 0.5lb + MVS SESSIONS Fig. 2 Rate of self-injurious behavior, including attempts, for sessions BL 0 Baseline; MVS 0 Matched vibratory stimulation next phase, the 0.23 kg (0.5 lb) weights were kept in place and contingent access to matched vibratory stimulation was added as a complementary intervention. Taylor s SIB decreased further in comparison to the 0.23 kg (0.5 lb) wrist weights condition and multiple days of zero SIB were observed. Following this phase, an attempt to verify the previous level of responding with 0.23 kg (0.5 lb) wrist weights was made. However, responding continued to be low with multiple zero days of SIB during this phase, and a subsequent phase in which 0.11 kg (0.25 lb) weights were used. When the weights were removed, and Taylor only wore the Velcro straps that housed the weights, his rate of SIB increased. Contingent access to matched vibratory stimulation was then allowed while Taylor wore the Velcro straps to evaluate whether that combination might result in a similar level of responding as was observed when access to matched vibratory stimulation was paired with the 0.23 kg (0.5 lb) wrist weights. After an initial decrease in SIB, Taylor demonstrated an accelerating trend in SIB. Therefore, the most successful intervention, 0.23 kg (0.5 lb) wrist weights with contingent access to matched vibratory stimulation, was reintroduced. During this phase, Taylor s rate of SIB declined to a level similar to the first time this intervention package was implemented, concluding with repeated sessions of zero SIB. Discussion The findings of the current study serve as a replication and extension of the previous literature examining the effectiveness of wrist weights and vibratory stimulation to

12 treat self-injury. Consistent with the literature regarding the use of wrist weights, SIB declined substantially when the weights were applied as a noncontingent antecedent intervention. In addition, we were able to fade the weights to a value of 0.23 kg (0.5 lb) and treatment gains were observed over a more extensive period of time (5 6 h per session) than previous studies have demonstrated. Although Taylor exhibited zero rates of SIB for the first time when wrist weights and matched vibratory stimulation were delivered as a treatment package, the current data set precludes reaching definitive conclusions regarding the role matched vibratory stimulation played in Taylor s reduced SIB during these phases. For example, low rates and a decreasing trend of SIB during the 0.23 kg (0.5 lb) phase (sessions ) that preceded the first 0.23 kg (0.5 lb) and matched vibratory stimulation phase (sessions ), suggests that repeated exposure to the weights may have resulted in greater decreases in SIB over time. In addition, when the matched vibratory stimulation was withdrawn, Taylor continued to display reduced SIB, including zero rate days, during the subsequent 0.23 kg (0.5 lb) (sessions ) and 0.11 kg (0.25 lb) wrist weight phases. Given the possibility that matched vibratory stimulation did indeed play a role in reducing Taylor s rate of SIB, future investigations may wish to assess its value as a treatment component in a manner which confers greater internal validity. Future evaluations of matched vibratory stimulation in isolation or combination with other interventions may expand the variety of treatments available to practitioners as they seek ways to improve the lives of those with developmental disabilities who engage in chronic SIB. As Piazza et al. (2000) stated, although unmatched stimuli may provide reinforcing consequences, a building state of deprivation for the sensory consequences related to problem behavior may ensue. As a result, unmatched stimuli may not effectively contribute to the reduction of problem behavior, particularly over long periods of time. In the context of these findings, there are several other limitations that warrant further discussion. Although previous investigators have demonstrated that adaptive behaviors are not negatively impacted by the introduction of wrist weights (e.g., Hanley et al. 1998; Van Houten 1993), we did not measure Taylor s adaptive behavior. Taylor s teachers did report that Taylor was much better able to participate in class activities as his rates of SIB decreased. At the start of the study, they reported, Taylor s SIB was so frequent and intense that a good portion of the day was spent addressing his clinical behavior, which interfered with his ability to complete academic tasks and engage socially with his peers and teachers. With regard to our experimental design, some of the phases in the study were brief, but we tried to balance having enough data to establish experimental control with our concern for Taylor s safety when less effective treatments were in place. If a given phase yielded an immediate increase in SIB, along with a clear change in the level of SIB, we discontinued the phase quickly. In terms of our measurement system, the percentage of sessions in which IOA was collected was adequate, but the percentage of total time in which IOA was collected was low relative to conventional standards. In terms of the mechanism underlying the effectiveness of wrist weights, there appears to be three leading explanations. Similar to Van Houten (1993), there was an immediate reduction in SIB following the first application of wrist weights, lending credence to the hypothesis that decreased rates of SIB are at least partially the result of increased response effort. However, if the effectiveness of wrist weights were

13 solely the result of engendering increased response effort, a dose-dependent effect should have materialized when the weight magnitude was reduced. In other words, one would expect SIB to be higher in the 0.91 kg (2 lb) condition in comparison to the 1.81 kg (4 lb) condition, and higher in the 0.45 kg (1 lb) condition in comparison to the other two higher weight conditions. However, this was not the case. Rates of SIB remained fairly consistent when the weights were gradually reduced. At a certain point, however, responding increased when lowering (as in the first 0.25 lb phase) or eliminating weights (as in the Velcro housing phase), and subsequently decreased when a heavier weight was reinstituted. It may have been that the use of wrist weights changed the response-reinforcer relationship between SIB and sensory consequences in that Taylor was not as able to generate as much force per blow given the increase in weight. Over time, if SIB resulted in degraded reinforcer value, Taylor may have become less motivated to engage in self-injury. It is also possible that the combination of wrist weights and the Velcro straps resulted in stimulus control over Taylor s responding. When some of the stimulus properties changed enough (e.g., the amount of pressure from the weights declined), the stimuli may have had less control over Taylor s responding. In terms of the matched vibratory stimulation, it appears that the massage unit provided sensory consequences in the same stimulus class as the effects of SIB, but we did not evaluate which component of the sensory stimulation (tension provided by the band or vibration) was most effective or necessary for potential treatment gains. Nonetheless, when Taylor had contingent access to matched vibratory stimulation and was wearing the 0.23 kg (0.5 lb) wrist weights, SIB was lower than the preceding two phases in which he was wearing only the 0.23 kg (0.5 lb) wrist weights (although the concerns related to internal validity that were previously discussed must be kept in mind). However, even with this package in place, Taylor did not exhibit a stable rate of zero SIB. In the early stages of each phase with the massager, Taylor may have attempted to produce high value sensory consequences by engaging in SIB while the massager was activated. Given that SIB in this context was punished by a time-out from access to the massager, Taylor s rate of SIB may have declined as he gained repeated contact with this consequence. In addition, it is likely that the massager itself did not fully match the sensory consequences of SIB given the lack of stable zero rates of responding and the less than satisfactory results when the massager was accessible when no weights were being worn (when Taylor was only wearing the Velcro straps). If Taylor also had access to vibratory stimulation that could be applied to the base of his palm and the cheekbone areas of his face (the other main areas stimulated when Taylor engaged in SIB), stable rates of zero responding may have been observed. Lastly, although the data suggest that matched vibratory stimulation can augment interventions that incorporate wrist weights, it is unclear how effective this type of stimulation would have been at the start of treatment, when Taylor was engaging in very high rates of SIB. Future investigations may wish to evaluate multiple forms of vibratory input that can more completely match the hypothesized sensory consequences of SIB maintained by automatic reinforcement. Acknowledgements The authors would like to thank Nicole Heal, Frank Bird, and Jill Harper for their input and support during the course of this project.

14 References Bailey, J., & Meyerson, L. (1970). Effects of vibratory stimulation on a retardate s self-injurious Behavior. Psychological Aspects of Disability, 17, Hanley, G. P., Piazza, C. C., Keeney, K. M., Blakely-Smith, A. B., & Worsdell, A. S. (1998). Effects of wrist weights on self-injurious and adaptive behaviors. Journal of Applied Behavior Analysis, 31, doi: /jaba Iwata, B. A., Dorsey, M. F., Slifer, K. J., Bauman, K. E., & Richman, G. S. (1994). Toward a functional analysis of self-injury. Journal of Applied Behavior Analysis, 27, (Reprinted from Analysis and Intervention in Developmental Disabilities, 2, 3 20, 1982). doi: /jaba O Reilly, M. F., Murray, N., Lancioni, G. E., Sigafoos, J., & Lacey, C. (2003). Functional analysis and intervention to reduce self-injurious and agitated behavior when removing protective equipment for brief time periods. Behavior Modification, 27, doi: / Piazza, C. C., Adelinis, J. D., Hanley, G. P., Goh, H., & Delia, M. D. (2000). An evaluation of the effects of matched stimuli on behaviors maintained by automatic reinforcement. Journal of Applied Behavior Analysis, 33, doi: /jaba Sandler, A. G. (2001). Sensory reinforcement strategies for the treatment of nonsocially mediated selfinjury. Journal of Developmental and Physical Disabilities, 13, Van Houten, R. (1993). The use of wrist weights to reduce self-injury maintained by sensory reinforcement. Journal of Applied Behavior Analysis, 26, doi: /jaba Wells, M. E., & Smith, D. W. (1983). Reduction of self-injurious behavior of mentally retarded persons using sensory-integrative techniques. American Journal of Mental Deficiency, 87,