When the Owner Feels Better: Understanding Bias and Placebo Effects in Veterinary Treatment

Exploring Cognitive Bias, Observer Bias, and Non-Specific Treatment Effects in Companion Animal Care

In human healthcare, the placebo effect is well established. But what happens in veterinary care, where the patient can’t speak? While animals may not experience placebo in the traditional sense, the caregiver placebo effect, observer bias, and non-specific treatment effects all play significant roles in shaping perceptions of success in veterinary treatment.

What is the psychology behind these effects? How they can influence both clinical decision-making and owner satisfaction, and what evidence tells us about reducing bias in animal care.

The Caregiver Placebo Effect: When Owners Perceive Improvement

Animals may not expect a treatment to work, but their caregivers often do — and those expectations can shape what they think they see.

A placebo-controlled study of dogs with osteoarthritis found that while 56% of owners reported improvement in their dog’s condition, only 8% showed objective improvement using force-plate gait analysis (JAVMA, 2012).

This discrepancy highlights how owner belief and hope can lead to overestimation of treatment effectiveness, especially in conditions involving chronic pain or subtle behavioral changes.

Cognitive Biases in Clinical Practice

Veterinary professionals are not immune to bias either. Cognitive biases affect how information is interpreted and can lead to confirmation of what a clinician expects to find.

Key types of bias include:

• Confirmation bias: The tendency to seek or interpret evidence in ways that affirm pre-existing beliefs
  
  
• Anchoring bias: Relying too heavily on initial impressions or diagnoses, even when new evidence arises
  

These biases are subtle but powerful. A review by McKenzie, (2014) in the Journal of the American Veterinary Medical Association emphasised how they can influence clinical reasoning and lead to overconfidence in unproven interventions (ResearchGate).

Observer Bias in Animal Studies

In studies involving animals, observer bias can lead to misinterpretation of subtle changes in behaviour, gait, or attitude.

A 2014 paper in Applied Animal Behaviour Science showed that observer expectations could significantly distort data collected during behavioral research, especially when outcomes are subjective (ScienceDirect).

Blinding observers to treatment groups is one way to mitigate this, but it’s not always feasible in real-world practice.

Non-Specific Treatment Effects: More Than Just the Medicine

Non-specific effects refer to any improvement not directly caused by the therapeutic agent — for example, the act of doing something, increased attention to the animal, or changes in routine.

A 2017 meta-analysis from BMC Veterinary Research compared conventional veterinary medications with homeopathy and found that non-specific treatment effects contributed significantly to owner-perceived improvements, even when the therapy itself was biologically implausible (PMC).

These findings support the need to separate true treatment efficacy from the “halo” created by the therapeutic encounter itself.

What Can Practitioners Do About It?

Veterinary clinicians and allied professionals can take several steps to minimise bias:

• Use objective measures: Where possible, rely on tools like force plate analysis, range of motion goniometry, or validated pain scales
  
  
• Blind assessments: Even informal blinding (e.g., different clinicians assessing progress) can reduce bias
  
  
• Manage expectations: Be transparent with clients about expected outcomes and the potential for bias
  
  
• Commit to continuing education: Awareness is the first step toward clinical objectivity
  

Implications for Canine Practitioners, Equine Specialists, and Animal Osteopaths

Understanding the influence of bias and non-specific effects is especially important for manual therapists like osteopaths, who often work in close partnership with animal owners. In canine and equine osteopathy, treatments typically involve subtle changes in mobility, comfort, and behavior; areas that are inherently difficult to measure objectively and highly susceptible to observational and caregiver bias.

For animal osteopaths:

• Client education is key. Owners may perceive improvement simply because they believe in the practitioner's skill or the hands-on nature of treatment. Transparent communication about what signs of change to look for and what timeframes are realistic, helps manage expectations.
  
  
• Objective baselines and reassessment tools, such as video gait analysis, behavioural logs, or validated pain scoring systems, can help practitioners more accurately assess changes over time.
  
  
• Referral and collaboration are vital when progress stalls or red flags appear. Maintaining a clear boundary between manual therapy and medical diagnosis ensures professional integrity and patient safety.
  

Whether you're working on a warmblood with sacroiliac pain or a Labrador with lumbosacral discomfort, grounding your practice in evidence and awareness of bias strengthens both outcomes and trust.

While animals don’t experience placebo effects directly, their humans, and sometimes their practitioners, do. Understanding and addressing caregiver placebo, cognitive biases, and observer effects is essential in making veterinary or manual treatment, such as osteopathy more objective, ethical, and evidence-based.

References

1. Conzemius, M. G., & Evans, R. B. (2012). Caregiver placebo effect for dogs with lameness from osteoarthritis. Journal of the American Veterinary Medical Association, 241(10), 1314–1319. https://pubmed.ncbi.nlm.nih.gov/23113523/
   
2. Brennen A. McKenzie, MA, VMD. (2014). Veterinary clinical decision-making: Cognitive biases, external constraints, and strategies for improvement. Journal of the American Veterinary Medical Association 244(3):271-6 .https://www.researchgate.net/publication/259768660_Veterinary_clinical_decision-making_Cognitive_biases_external_constraints_and_strategies_for_improvement
3. Sorge, R. E., & Oliver, M. H. (2014). Observer bias in animal behavior research. Applied Animal Behaviour Science, 158, 1–6. https://www.sciencedirect.com/science/article/abs/pii/S000334721400092X
   
4. Bergh, A., Lundin, F., & Pettersson, K. (2017). Evidence of placebo effects in veterinary homeopathy: A systematic review and meta-analysis. BMC Veterinary Research, 13, 301. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5738587/
   
   

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