Glossary
Placebo.
Direct answer
A placebo is a dummy treatment matching the product under test in appearance, taste and mode of administration, while lacking the supposed active component. It serves to separate the contribution of the active substance from everything the care situation itself produces: attention, observation, routine and expectation.
The placebo effect is not one single phenomenon: it mixes genuine expectation-driven change with natural course, measurement variation and altered husbandry. A placebo arm therefore does not measure the power of belief; it simply supplies the correct comparison value for the analysis. Without that value, any claim of effectiveness remains a mere assertion.
In horses it is more accurate to speak of a caregiver placebo effect: work on lameness assessment shows that people perceive improvement under dummy treatment that objective measurement systems do not confirm. The animal expects nothing, but the way it is moved, watched and judged changes. That is where the apparent success arises.
Control groupBlinding (single and double)Randomised controlled trial
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