Behavioral Interventions Behav. Intervent. 16: 111±125 (2001) DOI: 10.1002/bin.79 FUNCTIONAL ASSESSMENT AND TREATMENT OF PICA: A SINGLE-CASE EXPERIMENT John T. Rapp*, Claudia L. Dozier and James E. Carr University of Nevada, Reno, Nevada, USA The pica of a 6-year-old girl diagnosed with autism was initially shown to persist in the absence of socially mediated consequences. In an attempt to provide a competing source of oral stimulation, we used a stimulus preference assessment to identify food items that were subsequently presented noncontingently. However, the noncontingent schedule could not be thinned to a practical variation while still maintaining reductions in pica. A subsequent multielement evaluation of response blocking and verbal reprimands demonstrated that neither intervention both produced and maintained low levels of pica. Verbal reprimands were then used in conjunction with noncontingent food presentation, but this intervention did not produce signi®cant reductions in pica. Suppression of pica was ultimately obtained in both a clinic setting and in the child's natural environment using contingent, varied auditory stimulation. The results are discussed in the context of the `least restrictive alternative' model of treatment selection. Copyright # 2001 John Wiley & Sons, Ltd. INTRODUCTION Aberrant behavior maintained by automatic reinforcement has been deemed inappropriate for a variety of reasons (e.g., interference with educational training); however, such behavior is sometimes permitted in controlled contexts (see, e.g., Charlop, Kurtz, & Greenberg-Casey, 1990; Rapp, Dozier, Carr, Patel, & Enloe, 1999). However, pica, a behavior often found to occur in the absence of social consequences, is not acceptable at any level in any stimulus context due to health risks. These risks include intestinal blockage, poisoning, and parasitic infection (Fisher, Piazza, Bowman, Kurtz, Sherer, & Lachman, 1994; Foxx & Martin, 1975; Moncrieff, Koumides, Clayton, Patrick, Renwick, & Roberts, 1964). Therefore, successful assessment and treatment of automatically reinforced pica is of particular importance. Historically, however, this behavior problem has been dif®cult to treat. As it is typically classi®ed, the behavior of pica involves the ingestion of a wide range of inedible items. The variability in ingested stimuli might contribute to the dif®culty in treating this behavior. *Correspondence to: John T. Rapp, Psychology Department, University of Florida, Gainesville, FL 32611, USA. E-mail: jrapp@u¯.edu Copyright # 2001 John Wiley & Sons, Ltd. 112 J. T. Rapp et al. Piazza et al. (1998) recently conducted a multiphase study with three individuals who exhibited severe pica. After a functional analysis suggested that each participant's pica was maintained (at least in part) by a source of automatic reinforcement, the authors conducted stimulus preference assessments with food items that were similar (i.e., `matched') or dissimilar (i.e., `mismatched') to objects the individuals typically ingested. During subsequent treatment evaluations, continuous (i.e., noncontingent) access to matched stimuli reduced pica to nearzero levels for each participant. Similarly, Piazza, Hanley, and Fisher (1996) provided noncontingent access to a preferred food item in an attempt to reduce the cigarette pica of one participant. However, reductions in cigarette pica were observed only after the addition of a mild punishment procedure (i.e., response interruption), which was paired with the presentation of a purple card. In the presence of this card, pica reductions maintained across four generalization settings. In the present investigation, we ®rst conducted a functional analysis (Iwata, Dorsey, Slifer, Bauman, & Richman, 1982) to determine the variable(s) maintaining the pica of a young girl diagnosed with autism. Subsequently, we conducted a stimulus preference assessment to identify food items that might compete with pica. Finally, we attempted to treat the participant's pica using a noncontingent food (NCF) procedure similar to that reported by Piazza et al. (1996). After this intervention failed to eliminate pica, we evaluated the use of a variety of punishment procedures according to the `least restrictive alternative' model of treatment selection (Johnston & Sherman, 1993). Consequently, treatment progressed through the following interventions based upon level of intrusiveness: (a) NCF (®xed-time (FT) schedule delivery of a preferred food item) without punishment, (b) response blocking, and (c) verbal reprimands (evaluated in a multielement design), (d) NCF combined with contingent verbal reprimands (a `mild' punishment procedure), and (e) various levels of contingent auditory stimulation (a more `intense' punishment procedure). The result of this progression was the reduction of pica to near-zero levels across multiple stimulus conditions. PHASE 1: FUNCTIONAL ANALYSIS Method Participant and Dependent Variable Marisa was a 6-year-old girl diagnosed with autism who received 30 h of individual training per week in a university-sponsored program. Her receptive language skills consisted of approximately 100 words, while her expressive language was limited to Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) Functional assessment and treatment of pica 113 approximately eight words and several pictorial mands. Marisa had an extensive history of engaging in pica, which involved the ingestion of inedible objects (e.g., rocks, dirt, grass, balloons). Such objects were detected in Marisa's feces as often as three times per week. For the purposes of this investigation, pica was de®ned as the insertion of simulated pica objects (which were placed on the ¯oor) into the participant's mouth. Because of the potential dangers of consuming inedible objects, and the absence of medical staff supervision, we chose to bait Marisa's therapy room with edible objects (i.e., broken pieces of animal crackers) that resembled inedible objects found in Marisa's therapy room (e.g., pieces of ceiling tiles). Data Collection and Interobserver Agreement All sessions in this phase were conducted in Marisa's therapy room (9 feet12 feet) and were 5 min in duration. Data were collected with a video camera and scored using a real-time recording (RTR) procedure (Rapp, Carr, Miltenberger, Dozier, & Kellum, 2001). RTR involves the second-by-second recording of target behavior(s) and relevant events by scoring the exact time (from the VCR counter) of onset and offset of the events. With this method, videotaped sessions were scored on a secondby-second basis for occurrence and nonoccurrence of the target behavior using a scoring sheet marked for 300 s. Two independent observers scored 33% of the videotaped sessions in this phase. The mean point-by-point interobserver agreement (IOA) scores for occurrences and nonoccurrences of pica were 97% (range, 93.3% to 100%) and 99.5% (range, 99.3% to 100%), respectively. Experimental Design and Procedures A functional analysis (Iwata et al., 1982) was conducted to assess the variable(s) that possibly maintained Marisa's pica. A multielement design was used to assess levels of pica under four different experimental conditions. These conditions were no interaction, attention, demand, and a control (play) condition. For each session, the room was baited with approximately 50 items that could be ingested. All sessions were conducted in the same room. During the no-interaction condition, Marisa independently played with toys while a therapist read Marisa's therapy book. The therapist did not interact with Marisa (i.e., no consequences were provided for pica). This condition assessed levels of pica in the absence of social consequences. In the attention condition, Marisa was also given access to several toys while a therapist read Marisa's therapy book. Contingent on instances of pica, the therapist delivered a verbal reprimand (e.g., `Marisa, not in mouth'). This condition evaluated social positive reinforcement in the form of Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) 114 J. T. Rapp et al. attention as a potential variable maintaining pica. During the demand condition, a therapist presented Marisa with a nonpreferred academic training task (i.e., one that was frequently correlated with problematic behavior). Contingent on each instance of pica, the therapist withdrew the training task, turned away from Marisa, and withheld academic instructions for 20 s. Following this break period, the therapist re-initiated the task. Correct responses were followed by brief verbal praise, while other behavior was ignored. The purpose of this condition was to evaluate whether social negative reinforcement, in the form of the removal of a nonpreferred academic task, was a variable maintaining pica. The control (play) condition involved providing Marisa continuous access to toys in her room, as well as social interaction on an FT 15 s schedule. Results and Discussion Figure 1 shows high and undifferentiated levels of pica across the no-interaction (M7.3 per min), control (M6.9 per min), and demand conditions (M4.3 per min). In addition, slightly lower levels of pica were observed in the attention condition (M2.6 per min) in which verbal reprimands were provided contingent on instances of pica. Within-session analysis suggests that contingent social disapproval Figure 1. Occurrences of pica across functional analysis conditions. Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) 115 Functional assessment and treatment of pica may have served as a mild punisher, which increased the mean interresponse time (IRT) of Marisa's pica during this condition. Similarly, Marisa was initially compliant with prompts early in the demand condition sessions (e.g., for the ®rst minute), but eventually engaged in pica. This initial compliance may account for the slightly lower level of pica observed in this condition. Based on the functional analysis, we concluded that Marisa's pica was maintained by non-socially mediated variables (i.e., automatic reinforcement). PHASE 2: STIMULUS PREFERENCE ASSESSMENT Method Dependent Variables The de®nition of pica was the same as in phase 1. Food ingestion (scored separately for each food item) was de®ned as the placement, with subsequent chewing and swallowing, of a piece of food into Marisa's mouth. Data Collection and Interobserver Agreement Data collection, session length, and scoring were the same as in phase 1. In addition, IOA was calculated in the same manner as in phase 1. A second observer scored 30% of the sessions of this phase. The mean IOA score for nonoccurrences of pica was 100% (no pica occurred during this analysis). Similarly, the mean IOA scores for occurrences and nonoccurrences of food ingestion were 96% (range, 93% to 99%) and 99.2% (range, 98.9% to 100%), respectively. Procedure A paired-stimulus preference assessment (Fisher, Piazza, Bowman, Hagopian, Owens, & Slevin, 1992) was conducted to identify food items that might compete with the reinforcement produced by pica. Eight food items (graham crackers, carrot sticks, bread sticks, strawberry gelatin, un¯avored gelatin, banana, rice cakes, and tofu) were selected for this assessment based upon whether these items were similar (e.g., hard, crunchy) or dissimilar (e.g., soft, chewy) to the various non-food items Marisa typically ingested (similar to Piazza et al., 1998). These food items were cut or broken into comparably sized pieces and then presented three times (on a plate), in quasi-random pairings, across three separate days. For each session, the two food items were presented to Marisa (after she was seated at her dining table) on separate plates (side presentation was altered randomly). In Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) 116 J. T. Rapp et al. addition, pica objects were placed on the ¯oor on both sides of Marisa to determine whether the food items would compete with reinforcement produced by pica. During these sessions the number of food and pica items ingested was recorded. Results and Discussion The results from the stimulus preference assessment show that Marisa consistently selected and ingested rice cakes (M3.0 pieces per min), followed by strawberry gelatin (M2.7 per min), graham crackers (M2.3 per min), bread sticks (M1.0 per min), and tofu (M0.3 per min). Pieces of carrot sticks, banana, and un¯avored gelatin were never selected. The data indicate that Marisa consistently selected rice cakes, thus suggesting that she had a relative preference for this food item. Interestingly, although pica objects were available, and Marisa did not interact with some pairs of items (neither item was selected), she did not engage in pica during any of these sessions. Based on these results, rice cakes were used during the subsequent NCF phase. It is unclear why Marisa did not engage in pica when she was presented two food items with which she did not interact. Because of the brevity of these sessions, it is unknown how long Marisa would have remained seated in her chair and abstained from pica (in the presence of what appeared to be two nonpreferred food items). Based on clinical observations and the results obtained in the demand condition (see phase 1), Marisa typically did not remain seated for periods greater than approximately 5 min. During the demand condition, once Marisa left her chair, she always engaged in pica. As such, we speculate that the absence of pica during the paired-food sessions might have been the result of a prior history of receiving preferred foods (when less preferred items were refused), close supervision and prevention of pica during meals (when seated at a table), or both. In short, the absence of pica during these sessions appeared to be the result of stimulus control of sitting and proximity of the therapist, rather than the presence of two nonpreferred food items. PHASE 3: TREATMENT EVALUATION After conducting stimulus preference assessments for three individuals who exhibited automatically reinforced pica, Piazza et al. (1998) provided noncontingent access to the item identi®ed as most preferred for each. We attempted to systematically replicate this outcome by providing Marisa access to rice cakes (the most preferred food item from the stimulus preference assessment) on a dense schedule to compete with pica. After obtaining reductions with a dense food Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) Functional assessment and treatment of pica 117 presentation schedule, we then attempted to thin the schedule. When thinning was ineffective for producing zero levels of pica, more intrusive interventions were applied. The use of contingent auditory stimulation (e.g., 110±130 dB) has been shown to function as both a positive punisher and a negative reinforcer (Azrin, 1958). More recently, less intense contingent auditory stimulation has been utilized via the awareness enhancement device (AED) to eliminate automatically reinforced handto-head behaviors, such as hair pulling (Rapp, Miltenberger, & Long, 1998), and digit sucking (Ellingson et al., 2000). When worn by the respective individual, the AED emits an auditory stimulus (78 dB) contingent on the placement of the individual's hand within 6 inches of his or her head. Because the AED delivers the prescribed consequence independent of a social agent, it appears to be useful for reducing behavior maintained by automatic reinforcement. However, the AED delivers a contingent tone only after the behavior occurs for 1±2 s and, therefore, it is optimally applied to hand-to-head behaviors (e.g., hair pulling, digit sucking) that occur for extended periods of time. By contrast, pica is most often (as in the present case) a discrete hand-to-head behavior. Due to this fact, the AED currently does not lend itself well to detecting and delivering an auditory consequence for occurrences of pica. Therefore, in this phase of the investigation, an auditory stimulus that was controlled by a therapist was applied contingent on instances of pica during sessions when Marisa was alone. Method Dependent Variables The de®nition of pica was the same as in previous phases. Pica attempts were de®ned as the movement of either hand that contained a potential pica object above Marisa's waistline. Pica approaches were de®ned as a combination of the following behaviors: (a) Marisa moving either of her hands toward a pica object, (b) Marisa looking down toward a pica object, (c) Marisa leaning forward toward a pica object, and (d) Marisa bending at the knees when pica objects were at her feet. Data Collection and Interobserver Agreement Data collection and scoring were the same as in previous phases. In addition, IOA was calculated in the same manner as in previous phases. A second observer scored 28% of the sessions. Mean IOA scores for the occurrences and nonoccurrences of pica, pica attempts, and pica approaches (combined) were 93.6% (range, 92.5% to 100%), and 99.6% (range, 97.9% to 100%), respectively. Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) 118 J. T. Rapp et al. Experimental Design and Procedures Treatment sessions were conducted in Marisa's training room and were 5 min in duration. Marisa's therapy room was baited with the same simulated pica objects that were used in previous phases. Although toys were present in this room (placed in bins and shelves), these items were not readily accessible to Marisa until the second auditory stimulation phase was implemented. This alteration was made following our observation that Marisa attempted to acquire these items after experiencing the auditory stimulus (contingent on an instance of pica). Near the end of our treatment evaluation, 15±20 min probes were conducted in Marisa's training room and in the backyard of her home (a problematic setting for pica). A multielement design (to evaluate the milder punishers) with a series of reversals was used to evaluate the effects of four different treatments on the occurrence of pica. Baseline. The no-interaction sessions conducted during the functional analysis constituted the baseline phase. During these sessions the room was baited with simulated pica objects and a therapist was seated at a desk engaged in work activities. No consequences were provided for pica. Noncontingent food (NCF). During the NCF condition, a therapist presented a piece of a rice cake (determined in phase 2) on an FT schedule to Marisa during nointeraction sessions (a therapist interacted with Marisa only to provide the food item). Based on the mean IRT observed during baseline, we initially presented the food item on an FT 10 s schedule. We attempted to thin this schedule by 10 s when the level of pica was at or below 0.2 per min for two consecutive sessions. The schedule was made denser (i.e., returned to a previous schedule value) following two consecutive sessions above the same criterion. Attempts to thin the schedule were terminated following the failure of the initially thinned schedule (FT 20 s) to achieve the criterion, a return to the original NCF schedule (FT 10 s), and a subsequent failure of the thinned schedule. Response blocking. In this condition, the therapist physically guided Marisa's hand away from her mouth contingent on attempts to engage in pica. Otherwise, the therapist did not interact with Marisa or provide consequences for other behavior. Verbal reprimand. In this condition, the therapist delivered a statement of disapproval (as in the attention condition during phase 1) to Marisa contingent on pica attempts. Otherwise, the therapist did not interact with Marisa or provide consequences for other behavior. Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) Functional assessment and treatment of pica 119 NCFVerbal reprimand. This phase was conducted to assess the effects of a combination treatment that consisted of verbal reprimands and NCF. Although both NCF and verbal reprimands produced reductions in pica when implemented alone, neither resulted in the elimination of pica. Given that response blocking and verbal reprimands produced similar reductions in Marisa's behavior, the latter was selected for use with NCF due to its relative ease of implementation. Based on the results obtained during NCF, the criterion for thinning during this phase was altered depending on the schedule in place. We initially started with same response criterion used in NCF, but then reduced the rate requirement to zero for ®ve consecutive sessions at FT 10 s. Thereafter, we attempted to thin this schedule by 5 s when the level of pica was at or below 0.2 per min for three consecutive sessions. Alone. This condition was conducted to assess levels of pica when Marisa was alone. During these sessions, Marisa was alone in her therapy room and was viewed by two graduate students via a small glass window and TV monitor. No social consequences were provided for pica. Contingent auditory stimulation After NCF, response blocking, and verbal reprimands were evaluated, our treatment consisted of three separate phases of contingent auditory stimulation. During these phases, a 4 inch6 inch speaker was placed on the wall in Marisa's training room. Because a therapist was not required to dispense edibles on an FT schedule, these phases of the study took place when Marisa was alone. Marisa was observed on a monitor by a graduate student who controlled a CD player that contained a disc of pre-recorded tones. During each session, Marisa wore a yellow wristwatch that was intended to obtain inhibitory stimulus control over pica (similar to Piazza et al., 1996) based on its pairing with the auditory stimulus. However, it should be noted that the effectiveness of the wristwatch in obtaining stimulus control over pica was not experimentally evaluated in this study. In the ®rst auditory stimulation phase (AS1), an 83 dB tone was presented for 2±3 s (on an FR-1 schedule) contingent on instances of pica and pica attempts. During the second auditory stimulation phase (AS2), the tone and the target behaviors remained the same; however, the volume of the tone was increased to 90 dB. In addition, during the third session of this phase, although levels of pica began to subside, it became apparent that once an object was in Marisa's hand, she would ingest it (despite the contingent auditory stimulus). As placement of the item in Marisa's mouth appeared to be the terminal (reinforced) response in a chain of behaviors, we decided to deliver the auditory consequence for pica approaches (behavior that occurred earlier in the response chain) in order to prevent the terminal pica response. Finally, it appeared that the wristwatch had not developed stimulus control properties (i.e., Marisa engaged in pica while wearing the watch); therefore, Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) 120 J. T. Rapp et al. we attempted to increase the salience of this stimulus object by placing it in a freezer (to decrease its surface temperature) for several hours prior to each session. Although Marisa would look at the watch after it was placed on her wrist, its temperature did not appear to cause her any discomfort. In the third auditory stimulation phase (AS3), the target behaviors remained the same, but the auditory stimulus was changed such that four distinct tones were presented in a quasi-random order during the 2±3 s delivery. This was similar to the stimulus variation procedure reported by Charlop, Burgio, Iwata, and Ivancic (1988). Due to the use of varied tones, the volume ranged from 90 to 94 dB during this phase. Assessment/Treatment probes. After producing zero rates of pica in Marisa's therapy room, we assessed the effectiveness of the AS3 intervention during ®ve extended probe sessions. Based upon caregiver report, the most problematic setting in which Marisa engaged in pica was in her backyard during unsupervised playtime. This playtime was typically provided for 15±20 min periods each day. Naturalistic probes were initially 5 min in duration and were extended to 20 min. Next, we simulated Marisa's backyard (in her therapy room) by providing stimuli that she commonly ingested, as well as appropriate play objects, from that environment and assessed the effectiveness of the AS3 intervention under these conditions. Marisa's training room was furnished with one square foot of dirt, 40 square feet of sod, a small trampoline (to simulate a larger trampoline that was in her backyard), and several toys that were often available in her backyard. Finally, a naturalistic probe was conducted in the backyard of Marisa's home. If pica was observed during any of these sessions, the auditory stimulus was delivered as described in the AS3 condition. This was done to help promote generality of the response suppression. Results and Discussion Figure 2 shows that following high levels of pica during the initial baseline (M7.7 per min), NCF (M0.9 per min) on an FT 10 s schedule produced an immediate reduction to near-zero levels of pica. However, this reduction failed to maintain after the NCF schedule was twice thinned to FT 20 s. Moreover, to be of clinical signi®cance, a reduction to zero levels of pica was desirable. After a return to baseline resulted in highly variable levels of pica (M2.0 per min), neither response blocking (M0.8 per min) nor verbal reprimands (M0.7 per min) produced clinically signi®cant reductions in pica (the ®nal sessions of each condition indicated increasing trends). After the third baseline phase (M4.3 per min), NCF combined with verbal reprimands produced reductions in pica to near-zero levels during dense schedules of NCF. However, similar to the original NCF phase (without verbal Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) 121 Functional assessment and treatment of pica Figure 2. Occurrences of pica across baseline and treatment conditions. reprimands), gradual thinning of the NCF schedule, even with FR-1 verbal reprimands, did not maintain near-zero levels of pica. Following high levels of pica during the ®rst baseline phase in which she was alone (M7.3 per min), the implementation of AS1 failed to reduce Marisa's pica (M11.1 per min). In fact, it is possible that the tone used in this condition positively reinforced pica, evidenced by the higher-than-baseline rates that resulted. An increase in the intensity of the auditory stimulus during the AS2 phase resulted in a gradual reduction to zero rates of pica (M0.2 per min). A baseline probe conducted after AS2 resulted in an immediate increase in pica to a mean of 4.4 per min. The reimplementation of AS2 was marked by an initial decrease in pica; however, a return to zero rates of pica was not achieved. Problems with the auditory equipment during this phase resulted in a variable schedule of punishment that closely resembled a variable-ratio-3 schedule. It is speculated that the schedule produced by equipment failure, the possibility that Marisa habituated to the tone, or both, accounted for the persistence of Marisa's responding during this phase. It should also be noted that both the use of the cold watch and the presentation of the auditory stimulus for `approaches' began during the third session of this phase. This fact combined with equipment problems renders interpretation of the data from this phase dif®cult. Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) 122 J. T. Rapp et al. The introduction of AS3 was marked by the immediate and sustained reduction of pica to zero or near-zero rates (M0.01 per min). In addition, extended probes of 15 min and 20 min also resulted in zero rates of pica. Similarly, 15 min probes that were conducted in the training room with dirt and sod, and a naturalistic probe that was conducted in Marisa's backyard, resulted in zero and near-zero rates of pica. We hypothesized that zero rates of pica, as well as pica attempts (the auditory stimulus was not presented), during the naturalistic probe may have been due to inhibitory stimulus control exerted by the wristwatch. However, this effect was not experimentally assessed during this investigation. Although toys were accessible (they were in bins on shelves) prior to the AS2 phase, Marisa never manipulated objects that were present in her room when pica objects were simultaneously available. However, once reductions in pica were produced with contingent auditory stimulation, the percentage duration of object manipulation increased during the AS2 (M56.6%) and AS3 (M77.2%) phases, and maintained during the extended sessions (M51.4%) and naturalistic context probes (M94%). Moreover, following the contingent presentation of the respective auditory stimulus, Marisa began to manipulate an object within 7 s (the time required for her to walk across the room) for 43.8% of pica approaches, attempts, and occurrences. This may suggest that pica was a highly preferred behavior in Marisa's repertoire and that pairing the auditory stimulus with this behavior made it less preferred (through punishment); thus, an increase in another highly preferred behavior was observed. Put differently, when pica was unavailable to Marisa, toy manipulation became a preferred stimulus event. Alternatively, object manipulation may have been associated with the absence of the tone, though this position is less tenable as Marisa did attempt to engage in pica while simultaneously manipulating objects. GENERAL DISCUSSION This study illustrates the progression from less to more intrusive interventions for the persistent pica of a young child diagnosed with autism. When NCF, response blocking, and verbal reprimands produced inadequate reductions in pica, a contingent and varied auditory stimulus was utilized, which resulted in the suppression of pica. However, there were at least four limitations of the treatment evaluation that are worthy of discussion. First, the effects of the ®nal auditory stimulus intervention (AS3) were not replicated. A withdrawal and a subsequent reimplementation of the AS3 intervention would have provided stronger evidence for attributing the clinically signi®cant reductions of pica to this intervention. In addition, a conclusion about the effectiveness of the AS3 could have been more Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) Functional assessment and treatment of pica 123 convincing if the intervention had been carried out for a longer period of time. Likewise, as with the AS2 intervention, it is possible that the suppressive effects obtained with this intervention may have been lost following a return to baseline. However, this intervention was conducted in a clinic setting, which involved time constraints as well as caregiver opposition to an additional reversal. Second, the delivery of the auditory stimulus contingent on `pica approaches', beginning in the AS2 phase, was inconsistent with the response topography that resulted in auditory stimulus delivery in previous phases. It is possible that blocking and verbal reprimands may have been more effective had they been provided earlier in the chain of behavior (i.e., contingent on pica approaches rather than pica attempts). However, the treatment evaluation was conducted to reduce the occurrence of a potentially dangerous behavior while still permitting other behavior; this alteration was made to increase the potential effectiveness of the procedure. Third, the use of simulated pica objects (i.e., edible objects) may have made it dif®cult for Marisa to distinguish between objects that were consumable and items deemed unacceptable (because they were on the ¯oor) for ingestion. However, Marisa was only allowed to eat food items that were either delivered to her by a therapist or were placed on a plate while she was seated at a table. In addition, Marisa engaged in speci®c behaviors when she picked up objects from the ¯oor (actual pica objects or baited food) that she did not when she retrieved objects from her plate or from a therapist. These behaviors included jumping around the pica objects before reaching to the ground, then quickly grabbing the object and running to a corner of the room (presumably to avoid detection or a reprimand) to ingest it. These particular behaviors suggest that Marisa discriminated between these `edible' objects and inedible ones. Finally, the acceptability of the procedures utilized in this study was not evaluated. As a number of punishment procedures were used during the treatment evaluation, assessment of treatment acceptability would have provided further support of the use of more intrusive procedures for life-threatening behavior. In light of this limitation, it should be emphasized that Marisa's guardian was always aware of and approved of the programmed contingencies for Marisa's pica. The results of this investigation contribute to the literature in several ways. First, the use of NCF was shown to be ineffective for eliminating pica with schedules thinner than FT 10 s. Data from this study suggest that even highly preferred stimuli, provided on response-independent schedules, may not effectively compete with automatically reinforced pica. Second, this study is one of very few to use varied consequences (tones) to eliminate a target response. More speci®cally, this study adds to growing literature on the use of contingent auditory stimulation to eliminate automatically reinforced behavior. Third, the use of `natural stimuli' (i.e., dirt and sod) represents a novel attempt to integrate relevant stimuli into analogue Copyright # 2001 John Wiley & Sons, Ltd. Behav. Intervent. 16: 111±125 (2001) 124 J. T. Rapp et al. assessments in order to evaluate the generality of behavior suppression. Finally, as a whole, this study provides a logical progression from less to more intrusive interventions for life-threatening behavior. Although reinforcement-based procedures are obviously preferred approaches, the use of punishment procedures may become necessary when less intrusive measures fail to eliminate dangerous behavior. Unfortunately, unlike many behaviors maintained by socially mediated consequences, a rich and effective reinforcement-based technology for behavior that is incompatible with pica has yet to be developed. Future research could evaluate the bene®ts of and guidelines for using mild aversive interventions for life-threatening behavior that is resistant to less intrusive procedures. Similarly, research could focus on evaluating the presence of response hierarchies (e.g., Green & Striefel, 1988) so that suppression of the aberrant behavior, as seen in this investigation (with more intrusive interventions), might actually increase more socially desirable behavior (e.g., toy manipulation). ACKNOWLEDGEMENTS John Rapp and Claudia Dozier are now at The University of Florida. James Carr is now at Western Michigan University. The authors thank Kimberley Enloe and Ryan Pabico for their assistance with data collection. REFERENCES Azrin NH. 1958. Some effects of noise on human behavior. Journal of the Experimental Analysis of Behavior 1: 183±200. Charlop MH, Burgio LD, Iwata BA, Ivancic MT. 1988. Stimulus variation as a means of enhancing punishment effects. 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