“It must work because it works on animals and children” is a very common claim that is used to support the idea that various alternative remedies work. The reasoning is that animals and children do not understand the placebo effect, and perhaps that they're even being treated, therefore they will be immune from placebo responses; so any resulting improvement in their condition must be due to the alternative remedy working.
The crux of this argument is whether knowing they're being treated is necessary for placebo effects to occur in such patients and whether placebo responses are limited to the recipient of the medication.
In our article what is the placebo effect? we explain that there's no such thing as “the” placebo effect, it's better to think of it as an umbrella term for a collection of effects that are not specific to the medication given: some real, most not. So in order to assess this claim, it's necessary to realise that it's not simply a case of there being a placebo effect that either occurs or it doesn't, but that there may be many reasons for an alleged improvement in a condition in response to a remedy.
The scope of responses to medication
An assumption that's made in this argument is that responses to medication can only occur in the child or animal who's received it. This may be the case with physical responses to active ingredients when present in the medication but is it also true for placebo or other responses?
Claims of this nature are usually anecdotal but research has been carried out on giving medication to children where placebos were given to the control group. For example, Johnston et al. (2000) looked at the effect that giving Ritalin to children who had been diagnosed with ADHD had on their mothers' responses to their children's subsequent behaviour. The mothers made more positive evaluations regarding their children's behaviour when they knew their children were on medication – even when, unknown to them, their child was in the placebo group. This shows that a person's conclusion about how well a medication is working is at least partly influenced by their own expectation and interpretation.
Studies have also shown that the attitude and behaviour of the parent (caregiver, teacher, doctor, etc.) toward the patient can affect how the patient reacts. This effect is often called the “placebo effect by proxy”. It shows that a patient can be influenced by the mental state (positive attitude, etc.) and physical state (less stressed, etc.) of people interacting with them.
These findings are supported by a psychological feedback loop known as the “transactional model of interaction” which is a framework for explaining how one person's attitudes and behaviours can affect a second person's whose resulting behaviour affects the first's whose resulting behaviour affects the second's... and so on. It's usually invoked to explain how bad behaviour in children can be exacerbated by this sort of vicious cycle of interaction with their parents, but the model is applicable to all interactive situations.
This can explain how someone who's treated their child, baby or pet with a remedy that is unlikely to work (e.g. homeopathy) can become convinced that any resulting improvement (perceived or real) was caused by the remedy when in fact there may have been no change (the improvement is an expectation/reinterpretation effect in the parent/owner) or the change was brought about by a transactional interaction – or indeed, a bit of both.
What about professionals who use alternative remedies?
There are also claims from professionals such as doctors and vets who claim that alternative treatments work – often using their clients' anecdotes as their evidence. Can the claims of vets, for example, be treated in a similar way as just described?
It turns out that they can. The interactive model introduced above also applies to professionals; with the added factor of their authoritative position to be taken into account.
Vets, like doctors, hold a lot of power over their clients so when a vet tells a client that a remedy is working, the client has little reason to disbelieve them. It may seem unlikely that a healthcare professional would be fooled by ineffective remedies but being a doctor or a vet doesn't shield them from magical thinking and beliefs.
An example of a vet describing his own experience of veterinary homeopathy can be seen here in this letter that was published in the Veterinary Times: http://www.vetpath.co.uk/voodoo/edwards1.html
This letter illustrates, among other serious concerns, just how much influence professionals can have over their clients – something that will be enhanced if the client sought them out because they too believe in the alternative remedy.
Conclusion
The claim that certain alternative or complementary treatments must work because they work in animals and children seems like a convincing argument at first sight. However, it's not simply a case of “the” placebo effect not being present because of the child's or animal's lack of knowledge; there is a multitude of possible effects that could be pertinent as well as the interactive process and/or the practitioner's influence as described above.
Placebo effects can be induced (by proxy) in patients who are incapable of understanding or comprehending them, and psychological placebo responses can occur in people involved with the patient too. These effects can be enhanced when the authoritative influence of a professional is also present.