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

Manual Sign Mand Training and Prompt Delay for Increasing Vocal Responses: A Clinical Guide

Overview & Clinical Significance

The development of vocal verbal behavior in children with autism spectrum disorder and other developmental disabilities remains one of the most important and challenging objectives in behavior analytic practice. Many children receiving ABA services demonstrate limited or absent vocal repertoires, which significantly affects their ability to communicate needs, participate in educational settings, and engage in meaningful social interactions. The research by Carbone, Sweeney-Kerwin, Attanasio, and Kasper (2010) addresses this challenge by examining whether manual sign mand training combined with prompt delay can effectively increase vocal responding.

The clinical significance of this research lies in its practical approach to a persistent problem. Many practitioners have observed that some children with autism who are taught to communicate through manual signs begin to produce vocalizations that accompany or replace those signs over time. However, this phenomenon has not always been systematically studied or reliably replicated. By examining the specific procedural variables that may facilitate the emergence of vocal behavior during sign language training, this research provides practitioners with actionable information for their clinical work.

Mand training holds a privileged position in verbal behavior programming because mands are the first verbal operant to develop in typically developing children and because they are directly motivated by establishing operations. When a child mands, they are communicating to access something they currently want or need. This motivational component makes mand training a natural starting point for communication intervention. The question of how to transition from sign-based mands to vocal mands is therefore of considerable practical importance.

Prompt delay, also known as time delay, is a well-established procedure in the behavior analytic literature. By introducing a brief delay between the discriminative stimulus and the prompt, the procedure creates an opportunity for the learner to emit the target response independently before assistance is provided. When applied to vocal behavior during sign mand training, prompt delay creates a window during which vocalizations may emerge.

For practitioners working with children who have not yet developed functional vocal communication, this line of research offers a systematic approach that is both theoretically grounded in verbal behavior analysis and practically implementable in clinical settings. The approach does not require specialized equipment, can be integrated into existing programming, and builds on skills that many practitioners already possess.

Background & Context

The theoretical foundation for this research draws heavily from B.F. Skinner's analysis of verbal behavior, which categorizes verbal operants based on their functional relationships rather than their topography. Within this framework, a mand is defined as a verbal operant in which the response is reinforced by a specific consequence and is under the functional control of relevant establishing operations. Importantly, a mand can take any topographical form, including vocal speech, manual signs, picture exchange, or device-based communication.

The use of manual signs as an initial communication modality for children with autism has a long history in the field. Sign language offers several practical advantages as a starting point for communication training. Signs are always available (the learner always has their hands), they can be physically prompted through hand-over-hand guidance, and they provide a clear, discrete response that is relatively easy to shape. For children who have not yet developed vocal imitation skills, manual signs provide an accessible entry point into functional communication.

The relationship between sign language training and the subsequent emergence of vocal behavior has been documented in the clinical literature, though the mechanisms underlying this relationship are not fully understood. Several hypotheses have been proposed. One suggests that sign training establishes a communication repertoire that reduces the frustration and escape-maintained behaviors that may interfere with vocal development. Another proposes that the motor movements involved in signing may facilitate the development of motor imitation skills that generalize to oral motor imitation. A third hypothesis draws on the concept of automatic reinforcement, suggesting that once vocal responses begin to occur alongside signs, the auditory feedback from vocalizations may become automatically reinforcing.

The prompt delay procedure has been extensively studied across multiple response modalities and populations. The basic procedure involves initially providing the prompt simultaneously with or immediately after the discriminative stimulus (zero-second delay), then gradually increasing the interval between the stimulus and the prompt. This delay creates an opportunity for the learner to respond before the prompt is delivered, thereby promoting independent responding.

The combination of sign mand training with prompt delay represents a systematic attempt to create conditions under which vocal behavior is most likely to emerge. By establishing a strong sign mand repertoire first, the learner has a functional communication system. The introduction of prompt delay then creates opportunities for vocal responses to occur and be reinforced, without disrupting the existing communication repertoire.

This research is situated within a broader movement toward communication intervention approaches that prioritize functional outcomes while working to expand response topographies over time. Rather than viewing sign language and vocal speech as competing modalities, this approach treats signs as a bridge to vocal communication.

Clinical Implications

The clinical implications of this research extend across multiple dimensions of practice, from assessment and treatment planning to intervention implementation and progress monitoring.

At the assessment level, practitioners must evaluate the child's current vocal repertoire, including any existing vocalizations, vocal imitation abilities, and the contexts in which vocalizations occur. This assessment informs decisions about whether manual sign mand training with prompt delay is an appropriate intervention approach. Children who produce some vocalizations, even if inconsistent or non-functional, may be particularly good candidates because the prompt delay procedure can capture and reinforce these existing vocal behaviors.

Treatment planning should consider the selection of initial mand targets carefully. Items and activities with high motivational value should be prioritized because strong establishing operations increase the likelihood of mand responding. The vocal models provided during training should be simple, typically one or two syllable words, to maximize the probability that the child can approximate them. Practitioners should also consider the phonemic composition of target words, selecting words that include sounds the child has demonstrated the ability to produce.

Implementation requires careful attention to procedural fidelity. The prompt delay interval must be implemented consistently, and the differential reinforcement contingencies must be clearly established. When the child produces a vocal approximation during the delay interval, it should be reinforced immediately and enthusiastically, with the requested item or activity provided without requiring the sign. When the child produces the sign without a vocalization, the item is still provided, but the reinforcement may be of lesser magnitude or duration. This differential reinforcement arrangement shapes vocal responding without punishing the existing sign communication.

Generalization planning is essential from the outset of intervention. Vocal responses that emerge during structured mand training sessions must be programmed to generalize across settings, communication partners, and establishing operations. This may involve conducting training in multiple locations, involving multiple therapists and caregivers, and varying the specific establishing operations used to evoke mands.

Progress monitoring should track multiple dependent variables simultaneously, including the rate of sign mands, the rate of vocal mands, the rate of combined sign-plus-vocal mands, and the topographical accuracy of vocalizations. These data allow practitioners to evaluate whether the intervention is having the desired effect and to make data-based adjustments to the procedure.

Practitioners should also be prepared to modify the intervention if vocal responses do not emerge within a reasonable timeframe. The prompt delay interval may need to be adjusted, the reinforcement differential may need to be increased, or additional procedures such as echoic prompts may need to be introduced. Clinical judgment, guided by ongoing data analysis, is essential for making these decisions effectively.

Ethical Considerations

The ethical dimensions of communication intervention for children with limited vocal repertoires are substantial and deserve careful consideration. Several provisions of the BACB Ethics Code are directly relevant.

Code 2.01 requires informed consent before services are initiated. For communication intervention involving manual signs, practitioners must ensure that caregivers understand the rationale for the approach, including why sign language is being used as an initial communication modality and how it relates to the goal of developing vocal communication. Some caregivers express concern that teaching signs will reduce motivation to develop speech. Practitioners have an ethical obligation to address this concern directly and honestly, presenting the available evidence while acknowledging the limits of what can be predicted for any individual child.

Code 2.14 addresses the selection of least restrictive procedures. In the context of communication intervention, this standard supports approaches that build on existing strengths and expand communication options rather than restricting the child's current communication repertoire. Using manual sign training as a bridge to vocal communication is consistent with this standard because it adds communication capabilities without removing any existing skills.

Code 2.09 requires that treatment programs include provisions for ongoing modification based on data. This is particularly important in communication intervention, where progress may be slow and practitioners must be prepared to adjust procedures based on objective outcome data. Continuing an intervention that is not producing meaningful progress when alternatives are available would be inconsistent with this standard.

Code 1.05 on scope of competence is relevant because communication intervention requires specialized knowledge in verbal behavior analysis, augmentative and alternative communication, and developmental speech and language processes. Practitioners who lack sufficient training in these areas should seek additional education and supervision before implementing communication interventions, or should refer to colleagues with more specialized expertise.

Code 3.01 emphasizes acting in the best interest of the client. In communication intervention, this means that decisions about communication modality should be guided by the individual child's needs, abilities, and progress rather than by theoretical preferences or organizational convenience. If a child is making good progress with signs but not transitioning to vocal communication, the ethical response is to continue supporting effective communication through signs while exploring additional strategies for vocal development, not to withdraw sign language support in an attempt to force vocal communication.

The ethical obligation to consider the social validity of interventions is also relevant. Communication interventions should produce outcomes that are meaningful to the child and family in their daily lives, not merely statistically significant changes in laboratory-like conditions. Practitioners should regularly assess whether the communication skills being developed are functional, generalized, and valued by the child and their communication partners.

Assessment & Decision-Making

Effective clinical decision-making regarding the implementation of manual sign mand training with prompt delay requires a comprehensive assessment framework that addresses multiple domains.

The initial assessment should include a thorough evaluation of the child's current communication repertoire. This includes an inventory of existing vocalizations and vocal approximations, assessment of vocal imitation skills at various levels of complexity, evaluation of manual motor imitation abilities, assessment of current functional communication across all modalities, and identification of high-preference items and activities that can serve as mand reinforcers.

The Verbal Behavior Milestones Assessment and Placement Program (VB-MAPP) or similar criterion-referenced assessments can provide useful baseline data across verbal operants. However, practitioners should supplement standardized assessments with direct observation of communication behavior in natural settings, as some children demonstrate communication skills in natural contexts that may not be captured in structured assessment conditions.

Decision-making about whether to implement this specific intervention should consider several factors. First, does the child have a sufficient manual motor imitation repertoire to learn signs, or will motor imitation need to be established first? Second, does the child produce any vocalizations that could potentially be shaped into functional vocal mands? Third, are there strong establishing operations that can be leveraged for mand training? Fourth, is the child's learning history consistent with the ability to benefit from prompt delay procedures?

Once intervention has begun, ongoing assessment should drive all procedural decisions. The practitioner should establish clear decision rules in advance, specifying the conditions under which the prompt delay interval will be increased, decreased, or maintained. For example, if the child consistently produces vocal responses during the delay interval across three consecutive sessions, the delay may be increased. If vocal responses decrease or signs begin to deteriorate, the delay may need to be reduced.

The assessment of generalization should be built into the monitoring system from the beginning. Data should be collected not only during structured training sessions but also during natural communication opportunities throughout the day. Probes across settings, communication partners, and items should be conducted regularly to assess whether vocal mands are generalizing beyond the training context.

Decision-making should also address the question of when to consider alternative or supplementary approaches. If vocal responses have not emerged after a reasonable period of systematic implementation with good procedural fidelity, the practitioner should consider whether additional procedures are warranted, whether augmentative communication devices should be introduced, or whether the intervention goals need to be revised.

Caregiver input should be integrated into the assessment and decision-making process throughout intervention. Caregivers observe their child across a wider range of contexts than any clinician and may notice vocalizations or communication attempts that occur outside of structured sessions. Their observations and priorities should inform clinical decisions.

What This Means for Your Practice

For practitioners working with children who have limited vocal repertoires, this research provides a structured framework for using manual sign mand training as a stepping stone to vocal communication. Here are the key takeaways for implementation.

Begin by conducting a thorough baseline assessment of both vocal and motor imitation skills. This assessment will help you determine whether the child is a good candidate for this approach and will provide the comparison data you need to evaluate progress. Document the frequency and topography of any existing vocalizations, no matter how rudimentary.

When selecting initial mand targets, prioritize items with strong establishing operations and choose vocal models that are phonemically simple and include sounds the child has been observed to produce. This maximizes the probability that vocal approximations will emerge during the prompt delay interval.

Implement prompt delay systematically, starting with a zero-second delay to establish reliable sign manding, then gradually introducing delays that create opportunities for vocal responding. Be consistent with your differential reinforcement contingencies, providing more robust reinforcement for vocal responses while still reinforcing sign-only responses to maintain the existing communication repertoire.

Collect data on multiple response topographies simultaneously. Track sign-only mands, vocal-only mands, and combined sign-plus-vocal mands. This multi-dimensional data set allows you to identify trends and make informed procedural adjustments.

Involve caregivers from the beginning. Teach them the prompt delay procedure so that opportunities for vocal responding are created throughout the child's day, not only during structured therapy sessions. Caregiver involvement is often the factor that determines whether vocal responses generalize to natural communication contexts.

Finally, maintain realistic expectations while remaining optimistic. Not every child will transition from signs to vocal communication, and the timeline for this transition varies considerably across individuals. The goal is to provide the best possible conditions for vocal development while ensuring that the child always has access to functional communication.