12.1 Differential Reinforcement of Other & Low Rates of Behavior (DRO/DRL)

Differential Reinforcement of Other & Low Rates of Behavior (DRO/DRL)

Exam Tip: On the QASP-S exam, Differential Reinforcement of Other Behavior (DRO) is uniquely classified as omission training because reinforcement is contingent upon the non-occurrence of a target behavior during or at the end of a specified interval. You must know how to calculate initial DRO intervals from baseline Inter-Response Time (IRT), understand the critical difference between Interval and Momentary DRO, manage interval resetting contingencies, and recognize why DRO fails Ogden Lindsley's "Dead Man's Test." For Differential Reinforcement of Low Rates of Behavior (DRL), you must distinguish Full-Session, Interval, and Spaced-Responding subtypes and remember that DRL is strictly for behaviors acceptable in moderation—never for dangerous behaviors like aggression or self-injurious behavior (SIB).

In Applied Behavior Analysis (ABA), reducing challenging behavior while maintaining high rates of positive reinforcement is a cornerstone of ethical, client-centered intervention. When functional communication or simple extinction protocols are insufficient or must be augmented, clinicians turn to advanced differential reinforcement schedules. Among these, Differential Reinforcement of Other Behavior (DRO) and Differential Reinforcement of Low Rates of Behavior (DRL) offer specialized mechanics: DRO targets the total omission of a problem behavior, while DRL systematically lowers the rate of a behavior that is developmentally appropriate in moderation but disruptive at high frequencies.

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Conceptual Foundations of DRO (Omission Training)

First described in translational behavioral research by Reynolds (1961) and applied clinically across autism and developmental disabilities (e.g., Uhl & Sherman, 1972; Cowdery et al., 1990), Differential Reinforcement of Other Behavior (DRO) is a procedure in which a reinforcing stimulus is delivered contingent on the absence (omission) of the target problem behavior during or at specific times.

Operant Classification & The Omission Contingency

Technically, DRO is known as omission training. Unlike Differential Reinforcement of Alternative Behavior (DRA) or Differential Reinforcement of Incompatible Behavior (DRI), DRO does not specify an explicit, active replacement operant that must be emitted. Instead, the contingency is formulated as: $\text{If Target Behavior } (R_{\text{problem}}) \text{ does NOT occur for time } T \longrightarrow \text{Deliver } S^R$ $\text{If Target Behavior } (R_{\text{problem}}) \text{ occurs at any time during } T \longrightarrow \text{Withhold } S^R \text{ and Reset/Continue } T$

Because the reinforcement contingency is defined by what the learner does not do, any "other" behavior emitted during the interval is indirectly reinforced, provided the target problem behavior did not occur. This makes DRO exceptionally rapid at suppressing intense, entrenched topographies, but it introduces unique clinical challenges that require rigorous supervisory oversight.

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Variations of DRO Schedules: Interval vs. Momentary

DRO schedules are structured along two primary dimensions: (1) whether the absence requirement applies continuously throughout the entire interval (Interval DRO) or only at the specific instant the interval terminates (Momentary DRO); and (2) whether the time intervals are fixed (Fixed) or variable (Variable).

                               ┌───────────────────────────────┐
                               │    DRO SCHEDULE TAXONOMY      │
                               └───────────────┬───────────────┘
                                               │
                       ┌───────────────────────┴───────────────────────┐
                       ▼                                               ▼
          ┌─────────────────────────┐                     ┌─────────────────────────┐
          │      INTERVAL DRO       │                     │      MOMENTARY DRO      │
          │  (Absence throughout    │                     │  (Absence at the exact  │
          │   entire duration)      │                     │   moment timer lapses)  │
          └────────────┬────────────┘                     └────────────┬────────────┘
                       │                                               │
               ┌───────┴───────┐                               ┌───────┴───────┐
               ▼               ▼                               ▼               ▼
            FI-DRO          VI-DRO                          FM-DRO          VM-DRO
         Fixed-Interval  Variable-Interval               Fixed-Momentary Variable-Momentary

1. Fixed-Interval DRO (FI-DRO)

Under an FI-DRO schedule, a fixed, unchanging duration of time is established. The learner receives reinforcement at the end of the interval if and only if the target problem behavior did not occur at any point during that entire interval.

• Example: In an FI 3-minute DRO for severe vocal screaming, the technician sets a timer for 3 minutes. If the learner emits zero screaming across all 180 seconds, reinforcement is delivered at the 3-minute mark. If screaming occurs at second 42, the reinforcer is withheld, and the timer is immediately reset for a new 3-minute interval.
• Clinical Utility: FI-DRO is the most widely utilized initial DRO protocol for rapid behavior reduction because of its predictable structure and strong behavioral suppression effects.

2. Variable-Interval DRO (VI-DRO)

Under a VI-DRO schedule, reinforcement is delivered following the absence of the target behavior throughout intervals of varying lengths, which average to a predetermined mean duration.

• Example: In a VI 5-minute DRO, intervals might fluctuate semi-randomly across 3, 4, 5, 6, and 7 minutes (mean = 5 minutes). The learner must exhibit zero problem behavior for the duration of whichever interval is currently running.
• Clinical Utility: VI-DRO creates high resistance to extinction and prevents "scalloped" behavioral patterns where a learner misbehaves right after receiving reinforcement and calms down only when the next timer lapse approaches.

3. Fixed-Momentary DRO (FM-DRO)

Under an FM-DRO schedule, reinforcement is delivered at the conclusion of a fixed interval contingent solely upon whether the target behavior is absent at the precise moment the timer expires.

• The Critical Distinction: If the learner screamed during minute 1 and minute 2 of an FM 3-minute schedule, but is completely quiet at the exact instant the 3-minute chime sounds, the reinforcer is delivered!
• Clinical Utility: FM-DRO does not require continuous observation. It is exceptionally valuable in inclusive classrooms, group homes, or multi-student ABA settings where a teacher or technician cannot watch a client every single second. However, FM-DRO is significantly less effective for initial behavior reduction than Interval DRO.

4. Variable-Momentary DRO (VM-DRO)

Under a VM-DRO schedule, the technician checks for the absence of problem behavior at variable, unpredictable moments throughout the session. If the behavior is not occurring at that specific check, reinforcement is provided.

• Clinical Utility: Excellent for long-term maintenance and schedule thinning in natural community environments.

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Empirical Calculation of Initial DRO Intervals

A critical competency for the QASP-S supervisor is calculating the initial DRO interval using baseline behavioral data. Setting an arbitrary interval (e.g., guessing "5 minutes") almost always leads to treatment failure: if the interval is too long, the client cannot remain calm long enough to contact reinforcement, resulting in extinction of the intervention and behavioral resurgence.

The Baseline Inter-Response Time (IRT) Standard

The evidence-based standard requires setting the initial DRO interval at or slightly below the learner's mean baseline Inter-Response Time (IRT) (typically 80% to 90% of mean IRT).

$\text{Mean Baseline IRT} = \frac{\text{Total Duration of Baseline Observation}}{\text{Total Number of Target Problem Behaviors Emitted}}$

$\text{Initial DRO Interval} = \text{Mean Baseline IRT} \times 0.80 \text{ to } 0.90$

Step-by-Step Clinical Calculation Vignette:

• Clinical Case: A 9-year-old client with autism engages in intense skin-picking (excoriation) during independent table tasks.
• Baseline Data: During a 45-minute (2,700 seconds) baseline observation period, the behavior technician records exactly 15 discrete episodes of skin-picking.
• Step 1: Calculate Mean Baseline IRT: $\text{Mean IRT} = \frac{2,700 \text{ seconds}}{15 \text{ episodes}} = 180 \text{ seconds (3.0 minutes)}$ Interpretation: On average, the client engages in skin-picking once every 3 minutes. If the initial DRO interval were set at 5 minutes, the client would almost never succeed.
• Step 2: Set the Initial DRO Interval: Applying the 80% empirical buffer: $\text{Initial DRO Interval} = 180 \text{ seconds} \times 0.80 = 144 \text{ seconds (approximately 2 minutes, 20 seconds)}$ Clinical Decision: The QASP-S establishes an FI-DRO 2.5-minute (150-second) or FI-DRO 2-minute (120-second) schedule. Setting the interval slightly below the mean IRT guarantees that the client contacts reinforcement on approximately 85% to 90% of intervals, establishing immediate stimulus control.

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Resetting Contingencies: Interval Reset vs. No-Reset Rules

When implementing Interval DRO, the Behavior Intervention Plan (BIP) must explicitly define what technicians must do the moment problem behavior occurs.

1. Continuous Interval Reset Rule (Resetting DRO)

• Protocol: The instant the target problem behavior occurs, the technician immediately pauses and resets the timer back to zero. The client must demonstrate a full, unbroken interval free from problem behavior before receiving reinforcement.
• Behavioral Effect: Produces the most rapid and dramatic behavioral reduction because the client experiences immediate, direct consequences: every response directly delays reinforcement by the full interval duration.
• Clinical Example: In an FI 2-minute DRO for aggression, the client strikes the table at 1 minute and 45 seconds. The technician immediately resets the timer to 2:00. The previous 105 seconds of calm behavior are negated; the client must now go a full 2 minutes without aggression.

2. No-Reset Rule (Non-Resetting DRO)

• Protocol: If problem behavior occurs, the timer continues running to its conclusion. However, at the end of the interval, reinforcement is withheld. The timer then restarts for the next interval.
• Clinical Application: Used when continuous timer resets induce severe behavioral agitation, frustration, or catastrophic aggression in learners who track visual timers closely.

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The "Dead Man's Test" Caveat & Adventitious Reinforcement

While DRO is a potent tool in the behavior analyst's armamentarium, it carries two profound clinical hazards that every QASP-S supervisor must navigate.

Ogden Lindsley's Dead Man's Test

In 1965, pioneer behaviorist Ogden Lindsley articulated the Dead Man's Test: "If a dead man can do it, it is not behavior."

• A corpse can refrain from screaming, refrain from hitting, refrain from biting, and refrain from running away. Therefore, the non-occurrence of a behavior is not an operant response.
• DRO reinforces an absence, not an active skill. It creates a behavioral vacuum. While the client is not emitting problem behavior, they are not necessarily learning functional, prosocial, communicative, or academic repertoires.

Adventitious (Superstitious) Reinforcement of Secondary Maladaptive Behavior

Because DRO delivers reinforcement whenever the target behavior is absent, any other behavior occurring at the moment of reinforcement delivery will be strengthened by temporal contiguity.

• Clinical Scenario: A child is on an FI 3-minute DRO targeting severe aggression (hitting others). The child does not hit anyone during the 3-minute interval. However, at minute 2:58, the child begins spitting on the floor and ripping a textbook. At minute 3:00, the timer beeps. If the technician delivers the reinforcer because "no hitting occurred," the technician has adventitiously reinforced spitting and property destruction!
• Supervisory Protocol: The QASP-S must include an explicit "clean window" or secondary exclusion clause in the BIP: "If the client engages in any other severe challenging behavior (e.g., spitting, property destruction, flopping) within 15 seconds of timer expiration, withhold reinforcement and delay delivery until 15 seconds of appropriate behavior is demonstrated."
• Best Practice Mandate: Under QABA ethical guidelines, DRO should never be implemented as an isolated, standalone intervention. It must always be combined with Differential Reinforcement of Alternative Behavior (DRA) or Functional Communication Training (FCT) so the learner acquires constructive, functional replacement operants.

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Differential Reinforcement of Low Rates of Behavior (DRL)

In many clinical and educational situations, the target behavior is not inherently dangerous or socially unacceptable; rather, it becomes problematic solely due to its excessive frequency or rapid rate.

• Examples include: raising a hand in class to answer questions, asking the teacher for reassurance, blowing one's nose, requesting bathroom breaks, or eating food at a dangerously rapid pace (shoveling food).
• Completely extinguishing these behaviors using DRO or extinction would be clinically inappropriate and socially invalid. Instead, the clinician uses Differential Reinforcement of Low Rates of Behavior (DRL) to lower the rate of responding to an acceptable, socially normative level.

The Three Subtypes of DRL

                               ┌───────────────────────────────┐
                               │         DRL SUBTYPES          │
                               └───────────────┬───────────────┘
                                               │
         ┌─────────────────────────────────────┼─────────────────────────────────────┐
         ▼                                     ▼                                     ▼
┌─────────────────────────┐           ┌─────────────────────────┐           ┌─────────────────────────┐
│    FULL-SESSION DRL     │           │       INTERVAL DRL      │           │  SPACED-RESPONDING DRL  │
│  Reinforcer delivered   │           │  Session divided into   │           │  Reinforcer delivered   │
│  at end of session if   │           │  equal intervals; $S^R$ │           │  following a response   │
│  total responses <=     │           │  delivered if responses │           │  ONLY IF IRT >= minimum │
│  predetermined criterion│           │  within interval <= max │           │  temporal threshold     │
└─────────────────────────┘           └─────────────────────────┘           └─────────────────────────┘

1. Full-Session DRL

Under Full-Session DRL, reinforcement is delivered at the conclusion of an entire instructional session or observation period if the total number of target responses emitted during that session is equal to or less than a specified criterion.

• Clinical Example: A 7-year-old student raises his hand and calls out to the teacher 25 times per 45-minute reading period, monopolizing instructional time. Baseline rate is 25 per session. The QASP-S establishes a Full-Session DRL criterion of 10 or fewer hand-raises. If the student raises his hand 9 times during the 45-minute class, he receives preferred computer time at the end of the lesson. If he raises his hand an 11th time, reinforcement is withheld.

2. Interval DRL

Under Interval DRL, the total session is divided into a series of smaller, equal intervals. Reinforcement is delivered at the end of each individual interval if the learner emitted a number of responses equal to or below the predetermined criterion for that specific interval.

• Clinical Example: In a 60-minute session, the time is partitioned into six 10-minute intervals. The criterion is set at no more than 1 request for adult reassurance per 10-minute block. If the client asks 0 or 1 time during Interval 1, they receive a token at minute 10. If they ask a second time during that block, no token is earned for that interval, but Interval 2 begins with a fresh opportunity to earn.

3. Spaced-Responding DRL

Under Spaced-Responding DRL, reinforcement is delivered immediately following an occurrence of the target behavior, provided that a specified minimum Inter-Response Time (IRT) has elapsed since the preceding response.

• The Operant Mechanism: Spaced-responding DRL directly reinforces longer IRTs. If the learner responds too quickly (before the IRT requirement elapses), the response is not reinforced, and the IRT timer is reset to zero, requiring the learner to wait the full duration before their next response will produce reinforcement.
• Formula: $\text{Target IRT} > \text{Baseline Mean IRT}$
• Clinical Example (Rapid Eating Pace): A 14-year-old adolescent with autism eats food at a dangerously rapid rate, taking bites every 2 seconds (mean baseline IRT = 2s), creating severe choking hazards. The QASP-S implements a Spaced-Responding DRL with an IRT criterion of 15 seconds. The technician guides the client: after taking a bite, the client must wait at least 15 seconds before taking another bite. If the client waits 16 seconds and takes a bite, reinforcement is delivered (verbal praise and access to the bite). If the client reaches for a bite at second 8, the technician blocks the attempt, and the 15-second timer resets back to zero!

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Clinical Indications and Contraindications for DRL

The QASP-S must demonstrate clear clinical judgment regarding when DRL is appropriate versus when it is clinically dangerous.

Clinical Indications for DRL:

• Behaviors that have social validity and utility when emitted at moderate frequencies.
• Hand-raising, asking questions, contributing to classroom discussions.
• Greetings (saying hello to peers once, rather than repeatedly every 30 seconds).
• Self-advocacy and requests for assistance.
• Ingestion pacing (chewing food, sipping beverages).

Absolute Contraindications for DRL:

• Self-Injurious Behavior (SIB): Eye-gouging, head-banging, self-biting. It is medically and ethically unconscionable to implement DRL for SIB (e.g., "reinforcing a client for only banging their head 3 times per hour"). SIB must be reduced to zero.
• Physical Aggression: Hitting, kicking, or biting others. Zero tolerance is required to preserve bodily safety.
• Property Destruction & Fire-Setting: High-risk behaviors that threaten environmental safety.
• Elopement: Running into parking lots or leaving supervision.

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DRO vs. DRL Subtypes Comparison Matrix

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Clinical Decision Workflow for DRO vs. DRL