Using the Interval Timer for Differential Reinforcement

Alpaca’s interval timer can support clinically sound differential reinforcement procedures while preserving the integrity of interval-based data collection.

This article explains how to use the interval timer when reinforcement delivery takes time and should not be included in the observation interval.

A note to keep in mind when using intervals

In Alpaca, intervals advance automatically to support continuous observation. When using differential reinforcement, it’s helpful to think about what time you actually want counted as observation time.

Intervals are intended to capture behavior during observation, not the time spent delivering reinforcement. In many differential reinforcement procedures (DRO, DRA, DRI, DRL), reinforcement can take time and may interrupt observation.

If reinforcement time were included in an interval, it could unintentionally be counted as:

• absence of behavior

• on-task time

• a successful interval

To avoid this, clinicians can pause the interval timer during reinforcement and resume once observation can reliably continue. This helps ensure interval data reflect only true observation periods and remain clean and defensible.

Step 1: Set up your intervals

Before starting the session, configure the interval settings for the program or behavior target.

You will choose:

• Interval length (eg, 1 minute, 5 minutes)

• Time unit (seconds or minutes)

• Interval type

  • Partial interval

  • Whole interval

  • Momentary time sampling

These settings define the observation window only.

Step 2: Start interval timing

By default, Alpaca intervals auto-start and auto-advance:

• When one interval ends, the next interval begins immediately

• This supports continuous observation without gaps

This default works well for:

• Simple interval procedures

• High-rate behaviors

• Situations where reinforcement is brief (eg, verbal praise, token delivery)

Step 3: Pause the timer during reinforcement (when needed)

In many differential reinforcement systems, reinforcement:

• Takes time to deliver

• Requires transitions, setup, or a checklist

• Interrupts observation

Examples:

• Access to a preferred activity

• Token exchange

• Breaks or transitions

• Caregiver-mediated reinforcement

During data collection, you can click "Stop timer" to pause the intervals from advancing. Once you are ready for the observation window to begin again, you can click Stop Timer.

What to do in Alpaca

When reinforcement begins:

1. Stop or pause the interval timer

2. Deliver reinforcement

3. Resume the timer once reinforcement is complete and observation can reliably continue

Why this matters

Pausing the timer ensures that:

• Reinforcement time is not counted as interval success

• Data reflect only true observation periods

• Interval outcomes remain valid and interpretable

Step 4: Use Auto Start Interval intentionally

Alpaca allows you to choose whether intervals resume automatically after being stopped.

Auto Start Interval = Yes

• Intervals resume automatically

• Best for:

  • RBT-led sessions

  • Highly structured programs

  • Simple reinforcement procedures

Auto Start Interval = No

• Clinician manually restarts intervals

• Best for:

  • Complex differential reinforcement systems

  • Reinforcement with multiple steps

  • BCBA-led sessions or caregiver training

This setting gives clinicians control over fidelity without forcing a single workflow.

How interval outcomes are recorded

Each interval resolves to a binary outcome based on the selected interval type:

• Occurred / Did not occur

• Met / Not met

Reinforcement delivery does not change how the interval is scored.
It only affects when the next interval begins.

Clinical best practices

• Use shorter intervals early so learners contact reinforcement frequently

• Pair DRO procedures with a taught alternative behavior when appropriate

• Pause intervals whenever reinforcement meaningfully disrupts observation

• Avoid scoring data while reinforcement is being delivered

Example workflow

Procedure: Whole-interval DRO
Interval length: 5 minutes

1. Interval runs for 5 minutes

2. Timer ends → clinician determines if criteria were met

3. If met:

   • Timer is paused

   • Reinforcement is delivered

4. Once reinforcement is complete:

   • Interval timing resumes

   • Next observation interval begins

Reinforcement time is excluded from interval measurement.

Key takeaway

Alpaca’s interval timer is built to reflect how differential reinforcement is implemented in real clinical settings:

• Intervals = measurement

• Reinforcement = consequence

• Timer controls = fidelity protection

When in doubt, pause the timer during reinforcement to keep your data accurate and defensible.