Single-blind ABA Design — Single-blind ABA Reversal Design
Single-blind ABA Reversal Design · Also known as: single-blind reversal design, single-masked ABA design, single-blind withdrawal design, assessor-blind ABA design
The single-blind ABA design combines the three-phase reversal logic of the ABA single-subject design — baseline (A1), intervention (B), and withdrawal (A2) — with single-blind masking, in which outcome assessors are kept unaware of the current phase or treatment condition while the participant and intervention team remain aware. This blinding reduces observer bias in behavioral measurement across the three phases.
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When to use it
Use the single-blind ABA design when you need to demonstrate a functional relationship between an intervention and a reversible target behavior in an individual participant, and when observer bias is a plausible threat to measurement validity — particularly when the target behavior is rated subjectively (e.g., stereotypy, agitation, social engagement) rather than recorded by automated sensors. It is appropriate in clinical behavioral research, special education, rehabilitation, and pharmacological single-case studies where full blinding of all parties is impractical. Do not use this design when the target behavior cannot ethically be reversed (e.g., self-injurious behavior, acquired academic skills), when the logistic burden of blinding assessors (e.g., removing phase cues from video) is not feasible, or when automated objective measurement eliminates the observer bias that blinding is meant to address — in those cases a standard ABA or ABAB design may suffice.
Strengths & limitations
- Reduces observer expectancy bias in behavioral coding compared with a standard unblinded ABA design.
- Preserves the within-subject reversal logic that establishes functional relationships without a separate control group.
- Particularly valuable for subjectively rated outcomes where observer knowledge of phase could inflate or deflate estimates.
- Compatible with pharmacological single-case studies where medication condition can be concealed from assessors.
- Blinding integrity can be empirically verified, adding a transparent validity check to the study report.
- Full implementation requires that session recordings be stripped of phase cues, which may not be possible in real-time naturalistic observation settings.
- Blinding the assessor does not blind the participant or the implementer, leaving demand characteristics and intervention-delivery confounds unaddressed.
- Findings remain specific to the individual participant; generalization requires systematic replication across participants and settings.
- Ends in a withdrawal phase, leaving the participant without the intervention at study close — an ethical concern when the intervention is beneficial.
Frequently asked
What exactly is blinded in a single-blind ABA design?
In the single-blind variant, the outcome assessors — those who observe and rate the target behavior — are kept unaware of the current phase (A1, B, or A2). The participant and the person delivering the intervention are typically not blinded. This contrasts with a double-blind ABA design, where both assessors and participants (and sometimes implementers) are masked to condition.
How is blinding maintained when sessions are observed live?
Live real-time blinding is difficult; the most practical approach is to record sessions and have assessors rate randomized or de-identified clips after the fact, without access to session dates, sequence information, or phase labels. Where live observation is unavoidable, a separate assessor who was not present during intervention delivery can rate archived recordings.
Does adding single-blind masking change the reversal logic of the ABA design?
No. The three-phase sequence — baseline, intervention, withdrawal — and the reversal inference logic remain identical to the standard ABA design. Single-blind masking is a measurement-quality enhancement that reduces observer bias; it does not alter the experimental structure or the criteria for stability, phase transitions, or visual analysis.
When should I use a single-blind ABA design versus a double-blind ABA design?
Use single-blind when blinding only the assessor is feasible — for example, when the participant and therapist must know the phase for intervention delivery but session recordings can be rated blind. Use double-blind when both assessors and participants can be masked, such as in pharmacological studies where placebo conditions can credibly conceal treatment assignment from participants as well.
How do I check whether blinding was successfully maintained?
After all data are collected, ask each assessor to guess the phase assignment for each session they rated. If correct guesses do not exceed chance (approximately 33% for a three-phase design with equal phase lengths), blinding is considered intact. A significantly above-chance correct-guess rate suggests the blinding was compromised and should be reported as a study limitation.
Sources
- Baer, D. M., Wolf, M. M., & Risley, T. R. (1968). Some current dimensions of applied behavior analysis. Journal of Applied Behavior Analysis, 1(1), 91–97. DOI: 10.1901/jaba.1968.1-91 ↗
- Kazdin, A. E. (2011). Single-Case Research Designs: Methods for Clinical and Applied Settings (2nd ed.). Oxford University Press. ISBN: 978-0195341881
How to cite this page
ScholarGate. (2026, June 3). Single-blind ABA Reversal Design. ScholarGate. https://scholargate.app/en/experimental-design/single-blind-aba-design
Which method?
Set this method beside its closest kin and read them side by side — the library lays the books on the table; the choice is yours.
- ABA DesignExperimental design↔ compare
- ABAB designExperimental design↔ compare
- Multiple Baseline DesignExperimental design↔ compare
- Single-blind AB DesignExperimental design↔ compare
- Single-Subject Experimental DesignExperimental design↔ compare