By Matt Harrington, BCBA · Behaviorist Book Club · April 2026 · 12 min read

AAC Modalities for ASD: PECS, SGDs, and Apps in Functional Communication Training

Overview & Clinical Significance

Functional communication is one of the highest-priority outcomes in ABA services for individuals with autism spectrum disorder. When individuals cannot communicate their needs, preferences, and aversive experiences, problem behavior frequently fills that function. The selection of an appropriate augmentative and alternative communication modality — whether the Picture Exchange Communication System, a speech-generating device, a tablet-based app, or some combination — is therefore not merely a speech-language decision. It is a behavior analytic one with direct consequences for the individual's quality of life, their learning trajectory, and the safety and effectiveness of their environment.

Dr. Andy Bondy brings a distinctive perspective to this question: as the co-developer of PECS, he has both deep theoretical investment in one modality and extensive clinical experience observing its strengths and limitations relative to alternatives. This course benefits from that dual vantage point — it is not a promotional account of a single system but a clinically grounded examination of what different modalities offer and what questions practitioners must answer before recommending one over another.

For BCBAs, this topic sits directly at the intersection of scope of practice, competence, and functional communication training. The field has moved toward increasingly sophisticated AAC options, and practitioners who have not kept pace with the evidence base risk making recommendations that are based on familiarity rather than function. Conversely, practitioners who understand the behavioral mechanisms behind different modalities can make better individualized decisions, collaborate more effectively with speech-language pathologists, and set more meaningful communication targets across the full range of learners they serve.

Background & Context

The Picture Exchange Communication System was developed by Lori Frost and Andy Bondy in the late 1980s and published formally in the 1990s. PECS was designed specifically for individuals who lacked functional speech and who had not acquired communicative behavior through traditional language intervention approaches. The system teaches communication as an operant behavior from the outset — the first phase trains the individual to physically exchange a picture card with a communicative partner to request a preferred item. This exchange-based approach sidesteps the prerequisite of eye contact or verbal imitation that had blocked many nonspeaking individuals from accessing other communication systems.

Speech-generating devices (SGDs) have evolved substantially from early dedicated hardware to include sophisticated software running on tablets and smartphones. The behavioral mechanisms that make SGDs effective are similar to those underlying PECS — they provide a means of emitting a communicative response that produces access to reinforcers — but the output modality differs: SGDs produce synthesized or recorded speech, which may increase the likelihood of natural social reinforcement from communication partners unfamiliar with picture-based systems.

App-based AAC systems occupy a complex middle ground. The hardware (tablets, phones) is often less durable and more distracting than dedicated SGDs, but the cost is dramatically lower and the availability is far greater. The behavioral evidence base for specific app-based AAC systems is thinner than for PECS or dedicated SGDs, though research is growing. BCBAs must distinguish between the mechanism of action of AAC as a category — providing a means to emit communicative behavior that produces reinforcement — and the specific implementation characteristics of each system, which affect ease of acquisition, stimulus discrimination, and generalization.

Clinical Implications

The clinical implications of AAC modality selection extend well beyond the choice of system. Before any modality is selected, a functional communication assessment should identify what communicative functions the individual currently has — requesting, rejecting, commenting, labeling — and at what level of complexity. The mand, in Skinner's verbal behavior framework, is the primary target in early communication intervention precisely because it produces direct access to reinforcement: the individual asks, the reinforcer is provided, and the communicative behavior is strengthened. AAC systems that efficiently train the mand — that make it easy to emit the communicative response and ensure that response reliably produces the reinforcer — are the most appropriate starting points.

Scope of practice is a critical clinical consideration. BCBAs who recommend AAC systems without adequate competence in AAC assessment and selection may be operating outside Code 2.01 (Providing Effective Treatment) and Code 1.06 (Maintaining Competence). Collaboration with speech-language pathologists, who have graduate-level training in AAC assessment and intervention, is typically required for comprehensive AAC services. The BCBA's role often focuses on the behavioral acquisition procedures and the functional communication training framework, while the SLP contributes expertise in device selection, vocabulary organization, and symbol-based communication.

For learners who use problem behavior as a primary communicative function, AAC selection intersects directly with functional behavior assessment. If aggression functions as a request for escape, and the individual has no alternative means of requesting escape, the communication system must include vocabulary that allows that function to be expressed. AAC systems selected without reference to functional assessment may build communicative vocabulary that does not address the most pressing communicative needs — leaving the conditions that maintain problem behavior largely intact.

Ethical Considerations

Code 2.01 (Providing Effective Treatment) requires that practitioners recommend interventions, including communication systems, that are supported by current evidence and appropriate for the individual's needs. The AAC literature is rich and specific enough that general familiarity is insufficient — BCBAs need working knowledge of the evidence base for PECS, SGDs, and app-based systems, including what learner characteristics predict stronger outcomes with each.

Code 1.06 (Maintaining Competence) has direct application when practitioners are asked to implement AAC systems that are unfamiliar or that require technical knowledge they have not developed. Receiving training in a specific AAC system before implementing it — and seeking consultation from SLP colleagues when assessment complexity exceeds current competence — is an ethics requirement, not a professional courtesy.

Code 2.09 (Least Restrictive and Most Effective Practices) applies to AAC in a nuanced way. Some practitioners default to lower-tech AAC options (picture cards, simple boards) because they are more familiar and less expensive, without adequately assessing whether the learner would benefit from a higher-tech system that produces more natural social reinforcement and greater communicative flexibility. The principle of least restrictive practice does not mean defaulting to the simplest system — it means selecting the system that best supports the individual's communicative development with the resources available.

Consent and assent are particularly important in AAC decisions. Individuals with complex communication needs may have strong preferences about the modality they use to communicate, and those preferences constitute meaningful data. Where assent cannot be expressed verbally, practitioners should observe engagement and avoidance patterns across different modalities as proxy indicators of preference.

Assessment & Decision-Making

AAC modality selection should begin with a comprehensive assessment that addresses four questions. First: What communicative functions does the individual currently have, and which are most critical for quality of life? This determines what vocabulary and functions must be accessible in the system. Second: What are the individual's current motor, sensory, and cognitive characteristics, and how do these affect access to different modalities? Physical access to touch screens, manipulation of picture cards, and operation of device switches are all affected by individual motor profiles. Third: What are the communication partners' characteristics — their familiarity with the system, their capacity to respond consistently to communicative attempts, and their environment's capacity to support the system? A technically superior AAC system that communication partners cannot or will not use consistently will not produce functional communication. Fourth: What are the resources available — financial, technical, and in terms of training — to support implementation of different options?

The feature-matching approach to AAC selection evaluates different systems against the specific characteristics of the individual and their communication environment. BCBAs contributing to this process should be able to articulate the behavioral mechanisms by which each candidate system produces communicative behavior, what acquisition procedures are supported by evidence for each system, and what the research shows about generalization and maintenance for learners with profiles similar to the individual being assessed.

For PECS specifically, phase-based assessment determines where instruction should begin and what prerequisite skills are present. For SGD and app-based systems, feature assessment examines vocabulary organization, symbol type, motor access requirements, and speech output characteristics. These assessments should be conducted collaboratively with SLP colleagues for learners with complex profiles.

What This Means for Your Practice

For BCBAs working with nonspeaking or minimally verbal individuals with ASD, the most immediate practice implication is a commitment to evidence-based AAC decision-making rather than default to familiar systems. If your default recommendation for every nonspeaking learner is the same AAC approach, examine whether that recommendation is driven by evidence or by what you were trained on. Individual differences in motor profile, learning history, communication partner characteristics, and reinforcer accessibility mean that no single AAC system is optimal for all learners.

Functional communication training (FCT) — the process of teaching communicative behavior that replaces problem behavior serving the same function — should always be conducted within an AAC framework for learners who lack verbal speech. This means that the FCT vocabulary selected for each learner must match the function of their problem behavior. If the FBA indicates that aggression is maintained by escape from demands, the first communicative target in the AAC system must be a reliable means of requesting a break. Vocabulary that does not address functional needs will not produce the reinforcement contingencies needed to sustain communicative behavior and reduce problem behavior.

Collaboration with SLPs is not optional for comprehensive AAC practice. The BCBA who attempts to conduct full AAC assessments, device programming, and vocabulary selection without SLP involvement is operating beyond their scope of practice. The productive model is collaborative: SLP expertise in language, symbol systems, and device features pairs with BCBA expertise in behavioral acquisition procedures, functional assessment, and reinforcement-based training. Together these competencies produce more effective AAC services than either profession can deliver alone.

Finally, stay current with the app-based AAC evidence base. This is a rapidly evolving area where new products appear frequently and research lags commercial development. Critically evaluating new systems — asking what evidence supports them and whether their behavioral mechanisms are sound — is a professional responsibility in a field where families are often drawn to novel technology marketed with more enthusiasm than evidence.