Case Study

Reducing Incidents of Pica and Object Mouthing

ABA Therapy Case Study – 5-year-old girl

Behavior Plan: Reducing Incidents of Pica and Object Mouthing


Pica often occurs in individuals with developmental disabilities. Differential reinforcement procedures have been shown to decrease incidents of pica with some limited research. This case study examined the use of a A-B-A-B-C-B reversal design to decrease incidents of pica and object mouthing.  The reversal design comprised of a baseline phase, an intervention phase, a return to baseline, an intervention phase, an introduction to a second intervention phase, followed by a return to initial intervention.   


The Learner is a 5-year-old girl diagnosed with autism. She is currently receiving 18-hours of Intensive Behavior Intervention (IBI) per week. She has demonstrated repeated instances of pica (chewing and swallowing any inedible substance) and object mouthing (rubbing nonfood items on lips, teeth, or placing in mouth but not swallowing. These maladaptive behaviors occur while the Learner is engaged in various activities such as making a craft, playing with sand or playdough, etc.  The purpose of the intervention was to decrease incidents of pica and object mouthing.


The study was conducted using an A-B-A-B-C-B reversal design.

Baseline Data Summary

The pre-intervention assessment was conducted using two fundamental measures; count and interresponse time. Results demonstrated the amount of time that elapsed between the end of one occurrence of the response class and the beginning of the next was 7 minutes.  During baseline, the Learner engaged in pica and object mouthing over 50 times a day.  

Data Collection / Management

Baseline data was collected using the PortiaPro app.  Duration per occurrence data type was used to determine how long each incident persisted. As soon as the instructor therapist began the session she commenced the timer and ended the timer promptly contingent on the Learner engaging in the targeted behaviors.  During the intervention phase each fixed-interval trial was collected as well as a count of the maladaptive behaviors. The total count of incidents of pica and object mouthing per day were graphed.


The case study used a reversal design, which used repeated measures of behavior in a given setting that required an initial baseline phase, an intervention phase, a return to baseline, a reintroduction of the intervention phase, a second intervention phase, followed by a return to the preliminary intervention phase.

During baseline, the independent variable was absent. The behavior technicians  collected a total count of pica and object mouthing. The interresponse time was measured as well, which guided a suitable fixed interval for intervention. At the beginning of the session, the behavior technicians set the timer for the duration of the fixed interval and reinforcement was administered contingent on the absence of pica and object mouthing.  Reinforcement during the initial intervention was an edible (chips).  During this phase, if the Learner engaged in pica or object mouthing the timer was stopped, an edible was not provided and the technician blocked and redirected the Learner.

Lastly, the second intervention phase entailed the identical procedure as the preliminary intervention however, a different potent reinforcer (iPad) was delivered. The second phase was introduced to test whether or not a non edible reinforcer would maintain treatment effects. Throughout this phase when the Learner was successful for the fixed interval, a 30-second video clip on the iPad was presented to the Learner as a reinforcer.


Reducing Incidents of Object Mouthing and PicaDuring the initial baseline the Learner engaged in pica and object mouthing 50 and 55 times per day. Following the introduction of the DRO procedure, a 4-minute time interval, a significant decrease was observed with 13 instances recorded on the first day of the intervention. A return to baseline caused an increase of incidents however, not as elevated as the incidents in the initial baseline phase.  When we returned to the intervention (chips) a steady decrease of incidents was observed. A second intervention (iPad) was implemented on days 11-13 which sustained the steady decreased level of target behaviors.  During the final condition the independent variable (chips) remained in contact with the behaviors and a stable trend continued at a lower rate than baseline.


The results indicate that the use of a fixed-interval differential reinforcement of other behavior contingent on the absence of problem behavior decreased the total frequency of pica and object mouthing per day, regardless of whether the reinforcer was edible or nonedible. The potency of the reinforcer was most important.  One important implication to consider are possible sequencing effects as a result of the preceding condition. As we did not return back to the baseline phase before executing the second intervention we may have confounding influences on the total incidents of pica and object mouthing during the second intervention. It should be pointed out that returning to baseline levels of responding before introducing the second treatment condition reduces the threat of sequence effects. Future intervention to thin the fixed interval DRO is in progress as the trend in the current data is not showing any further deceleration. Extinguishing pica and object mouthing can be challenging as it is not possible to completely sanitize the  natural environment for competing items for ingestion or mouthing.  Further consideration around implementing a DRI (Differential Reinforcement of Incompatible Behavior) procedure in addition to the DRO are in progress and recommendations have been made for testing to rule out any nutritional deficiencies.


Cooper, J. O, Heron, T.E & Heward, W. L. (2007). Applied Behavior Analysis, 2/E. Pearson Education Inc

Young, S. (2011).  Craving Earth: Understanding Pica: the Urge to Eat Clay, Starch, Ice, and Chalk. New York: Columbia University Press.



Margherita Curcio
Charlene Gervais, M.ADS, BCBA
Clinical Director, The Portia Learning Centre



The information in this case study is for general information purposes only and is not intended to provide any type of professional advice. Portia does not guaranty the accuracy or reliability of any information contained in this case study from third party sources. You should consult a Board Certified Behavior Analyst or other qualified professional for specific advice. Portia International assumes no responsibility for any reliance made on or misuse or omissions of the information contained in this blog.

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