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

Teaching Matching-to-Sample: Visual Discrimination and Early Learning Skills in ABA

Overview & Clinical Significance

Matching-to-sample (MTS) is a foundational discrimination learning procedure in which the learner is presented with a sample stimulus and selects the comparison stimulus that matches it from an array. In applied behavior analysis, matching is one of the earliest and most important prerequisite skills in skill acquisition programs — it provides the perceptual and cognitive infrastructure for reading, categorization, mathematics, and symbol-based communication systems including PECS and AAC devices.

For learners with autism spectrum disorder and related developmental disabilities, matching skills assessed through the VB-MAPP provide a window into the learner's visual discrimination capabilities, attentional focus, and readiness for more complex academic and communicative learning. A learner who cannot reliably match identical objects cannot reliably distinguish between PECS picture cards, letter tiles, or number symbols — making matching mastery a clinical prerequisite for a broad range of subsequent instructional goals.

From a verbal behavior perspective, matching-to-sample is the behavioral basis for categorization and for understanding the equivalence relationships between stimuli — relationships that underlie the development of derived stimulus relations and, by extension, generative language. A learner who can match on the basis of category membership is demonstrating a form of conceptual behavior that reflects emerging language-related repertoires.

For RBTs and ABATs implementing matching programs, the VB-MAPP framework provides a developmentally sequenced roadmap: from identical object matching, to non-identical object matching, to picture-to-object matching, to picture-to-picture matching, to matching by category, function, or abstract property. This sequence reflects the typical developmental progression and guides the clinical sequencing of matching targets in individualized skill acquisition programs.

Background & Context

The experimental study of matching-to-sample has a long history in the behavior analytic literature, dating back to studies of generalized identity matching, conditional discrimination, and stimulus equivalence. Sidman's foundational work on stimulus equivalence demonstrated that organisms trained to match stimuli in specific configurations would, without additional training, demonstrate new matching relationships — a finding with profound implications for understanding the development of symbolic behavior and language.

In applied settings, matching-to-sample procedures have been validated as effective instructional tools for teaching a wide range of discrimination skills to learners with developmental disabilities. The VB-MAPP includes matching milestones at multiple developmental levels, recognizing matching as a prerequisite skill that develops in tandem with early vocal and non-vocal language. The ABLLS-R similarly includes matching as a foundational category.

The concept of derived stimulus relations — emergent matching performances that arise from training on a smaller set of stimulus relations — has significant clinical implications. A learner trained to match spoken words to pictures and trained to match pictures to objects may, without additional training, demonstrate the ability to match spoken words to objects. This derived relation represents a fundamental mechanism of language learning and is the applied basis of language-based matching interventions.

Error analysis in matching programs provides important information about the learner's discrimination capabilities. Position preferences — consistently selecting the rightmost or leftmost comparison — indicate that the sample stimulus is not controlling the matching response. Perseverative errors — selecting the same comparison regardless of the sample — suggest that the matching instruction is not establishing stimulus control. These patterns guide instructional modifications.

For supervisors, matching programs are often the earliest programs implemented with new clients and new RBTs. Because matching provides a foundation for so many subsequent skills, implementation errors — inconsistent array arrangement, failure to rotate positions, reinforcing incorrect responses during correction, premature advancement — can create discrimination problems that impede progress across multiple skill areas.

Clinical Implications

Matching instruction progresses through a developmental hierarchy. Identical object matching is the earliest and most concrete form, requiring discrimination on the basis of three-dimensional physical similarity. Non-identical object matching requires discrimination on the basis of category membership rather than identical appearance. Picture-to-object matching requires cross-modal discrimination between a 2D representation and a 3D referent. Picture-to-picture matching requires discrimination within a visual array. Each step represents an increase in abstraction and requires mastery of the preceding level.

Array size and discrimination difficulty are the primary variables controlling task complexity. Programs begin with identity matching with a single comparison and systematically increase the array size as the learner demonstrates accurate discriminating. Similarly, the similarity of distractors to the target is the primary manipulation for adjusting discrimination difficulty within a given array size.

Position rotation is a procedural control that prevents position biases from developing. When the correct comparison stimulus is always in the same position, the learner may match by position rather than by stimulus features. Systematically rotating the positions of all array items across trials ensures that position is not a reliable cue, forcing the learner to respond on the basis of the sample stimulus.

Category-based and function-based matching extends the matching repertoire from perceptual similarity to conceptual organization. Teaching a learner to match a fork to a plate and a cup on the basis of mealtime function requires that the function category has been established as a controlling variable. This form of matching underlies the organization of knowledge and the categorization skills that support academic and social learning.

Data collection in matching programs should track both accuracy and, where relevant, latency. Accurate but very slow matching may indicate that the learner is searching the array rather than responding under stimulus control of the sample. Review of error patterns — which distractors are most frequently selected incorrectly — guides modifications to the array and the instructional sequence.

Ethical Considerations

Code 2.01 supports the use of matching-to-sample procedures as empirically supported discrimination training methods. The evidence base for MTS in establishing visual discrimination and supporting symbolic behavior development is extensive, spanning both experimental and applied research.

Code 2.09 applies to the physical arrangement of matching tasks. When matching involves placing objects, physical guidance may be used during initial instruction. This guidance must be delivered with the minimum contact needed and faded systematically. Programs using physical guidance for matching should specify the prompt fading procedure in writing.

Code 1.05 (cultural responsiveness) is relevant to stimulus selection. The objects, pictures, and categories used in matching programs should reflect the learner's cultural context and daily life. Using stimuli from the learner's home environment — common household objects, foods familiar in the learner's culture, family photographs — increases the functional relevance of matching instruction and supports generalization to natural settings.

Code 4.05 requires that supervisors train and observe RBTs implementing matching programs before approving independent implementation. Matching programs may appear simple, but position biases, array rotation failures, and incorrect error correction procedures are common errors. Direct observation and specific procedural feedback are prerequisites for reliable implementation.

Assessment & Decision-Making

VB-MAPP Matching assessment provides a developmental map of the learner's current matching repertoire, identifying which forms are mastered and which represent instructional targets. The milestones specify matching skills at developmental levels from 0-18 months through 48 months, allowing BCBAs to identify the learner's profile and select targets at the next appropriate complexity level.

Pre-instructional assessment of reinforcer potency is relevant to matching programs because effectiveness depends on the availability of reinforcing consequences for correct responses. Matching programs implemented without potent reinforcers will produce poor acquisition regardless of procedural correctness.

Error pattern analysis guides instructional modifications. If the learner shows consistent position biases, the first modification is more frequent position rotation and potentially presenting only two-item arrays. If the learner shows consistent distractor errors to a specific foil, the array should be modified. If the learner shows inconsistent responding with no clear pattern, stimulus salience should be evaluated.

Decision rules for advancing through matching levels should specify mastery criteria that include generalization to novel stimuli. A learner who matches correctly only with the specific training objects has not demonstrated the generalization of the matching concept. Probes with novel stimuli should be built into the program plan.

What This Means for Your Practice

Matching programs are a cornerstone of early ABA skill acquisition, and their quality determines the foundation on which subsequent reading, math, categorization, and AAC skills are built. Invest supervisory attention in both the technical accuracy of implementation and the clinical sequencing of targets. A learner who has robust generalized identity matching, strong picture-to-object matching, and emerging category-based matching is far better positioned for literacy and academic instruction than one who has only trained a small set of specific matching pairs.

Position biases are among the most common matching program problems and the easiest to prevent. Require RBTs to document array arrangements across trials and demonstrate systematic position rotation during supervision observations. Reviewing data graphs for perseverative correct responding — high accuracy sustained even when the sample changes — is a quick way to detect position biases inflating accuracy data.

Generalization probes should be built into every matching program from the beginning. Using novel objects and pictures — not only training stimuli — for periodic probes tests whether the learner is matching on the basis of the targeted stimulus features or only familiar objects. When generalization probes show poor performance, the program needs multiple-exemplar training using a broader range of stimuli.

Connect matching skills explicitly to subsequent programming. When a learner masters picture-to-picture matching, immediately begin building toward the discrimination skills needed for PECS Phase III. When a learner masters category-based matching, begin using those categories in intraverbal programming and receptive identification tasks. Matching is infrastructure for the communicative and academic repertoires that follow.

Use the VB-MAPP matching profile when communicating with families and IEP teams. The developmental framework provides a shared language for describing the complexity of matching instruction that makes the clinical rationale for target selection accessible to caregivers and non-ABA team members.