Evaluating the Effects of Compound Stimuli on Stimulus Control in Match-to-Sample Learning

Introduction

Teaching new concepts effectively is a priority for many behavior analysts, especially those working with individuals with developmental disabilities. One widely used teaching method is match-to-sample (MTS), where learners match stimuli based on shared characteristics. However, how we present stimuli within these tasks can significantly impact learning outcomes.

A recent study by Grey, Morris, Perrin, and Oliveira (2024) explored how compound stimuli—a combination of two or more visual elements—affect stimulus control in MTS procedures. Their findings highlight potential challenges and provide guidance for designing more effective instructional strategies.

In this blog, we’ll break down the key concepts, summarize the study’s findings, and discuss what behavior analysts can take away from this research to enhance their teaching methods.

What Are Compound Stimuli?

In behavior analysis, compound stimuli are used to teach concepts by simultaneously presenting multiple elements, such as a picture paired with a word. These combinations are common in educational settings, particularly for learners who require extra support in acquiring new skills.

Potential Benefits of Using Compound Stimuli:

1. Enhanced learning efficiency – Presenting related stimuli together may help learners grasp concepts more quickly.
2. Facilitation of emergent relations – Learners may develop connections between stimuli that were not directly taught.
3. Flexibility across instructional settings – Compound stimuli are easily incorporated into various learning environments.

Risks and Challenges:

1. Restrictive stimulus control – Learners may become reliant on one component of the stimulus rather than responding to both elements.
2. Overshadowing effects – One part of the compound stimulus may dominate the learner’s response, preventing full understanding.
3. Blocking effects – Exposure to a compound stimulus may hinder the learner from independently recognizing its individual elements.

These risks emphasize why behavior analysts must carefully evaluate stimulus control when using compound stimuli in teaching.

Why Is Stimulus Control Important?

Stimulus control occurs when behavior is influenced by the presence of a particular stimulus. In effective teaching, learners should respond correctly to relevant stimuli and generalize learned skills across different contexts.

When using compound stimuli, however, issues can arise:

• Learners may respond only to certain features (e.g., relying on pictures while ignoring words).
• They may fail to demonstrate emergent relations, meaning they do not generalize their learning to new situations.
• If restrictive control develops, learners may struggle with independence when trained stimuli are no longer presented together.

Recognizing and addressing these issues is crucial for designing effective interventions.

The Study by Grey et al. (2024): Goals and Methods

Study Objectives

The researchers aimed to:

1. Assess whether learners demonstrated restrictive stimulus control when learning with compound stimuli.
2. Determine if knowledge generalized to individual stimulus components (e.g., could learners still identify words when pictures were removed?).

Participants

The study involved six learners, ages 10–16, from a special education setting. All participants had developmental disabilities, including Autism Spectrum Disorder and Down Syndrome.

Materials and Experimental Setup

Stimuli included three main types:

1. Compound stimuli – A picture paired with a printed word.
2. Picture-only stimuli – Pictures presented without words.
3. Word-only stimuli – Words presented without pictures.

Learning sessions involved:

• Baseline training with compound stimuli.
• A stimulus component evaluation phase, testing whether participants could respond accurately when stimuli were presented separately.
• A multi-element design to compare performance across different stimulus formats.

Key Findings

1. Baseline Performance: When presented with compound stimuli (picture + word), all six participants demonstrated at least 80% accuracy in selecting the correct matches.

2. Stimulus Component Evaluation: Accuracy declined significantly when stimuli were presented in isolation.

   • Word-only stimuli were the most challenging; most participants performed below the accuracy threshold.
   • Picture-only stimuli led to better performance, but some participants still struggled.
   • One participant showed difficulty responding to both words and pictures individually.

3. Conclusions: Many participants relied exclusively on picture features when compound stimuli were used in teaching. As a result, stimulus control did not transfer effectively when words were presented on their own.

Implications for Behavior Analysts

This study raises important points for anyone designing instructional programs that use compound stimuli.

Key Takeaways:

1. Identify and assess restrictive stimulus control early on – Before assuming a learner has acquired a skill, test their ability to respond to each stimulus component independently.
2. Consider fading compound stimuli systematically – To ensure generalization, start with compound stimuli but gradually introduce single components.
3. Use generalization probes – Regularly test whether learners apply their learning when stimuli are presented in different formats.
4. Don’t assume successful MTS responses indicate full learning – Just because a learner responds correctly to a compound stimulus doesn’t mean they understand the individual components.

Behavior analysts working with individuals with developmental disabilities can improve outcomes by ensuring that instruction leads to flexible, generalized learning rather than reliance on specific stimulus configurations.

Final Thoughts

The research by Grey et al. (2024) highlights the importance of evaluating stimulus control when training learners with compound stimuli. While combining pictures and words can be beneficial, we must also ensure that learning generalizes beyond the training context.

By applying these findings, behavior analysts and educators can design better interventions that promote true skill acquisition, flexible responding, and independence for their learners.

For further details, you can read the full study here:
📖 DOI: 10.1007/s40617-024-00990-6