The influence of the experimenter’s expectancy in the results of the assessment of appeasing pheromones in stress of police dogs during training 

© J. Dehasse*, S. Schroll

3 avenue du Cosmonaute, 1150 Brussels, Belgium
Speech given at the 5th International Veterinary Behavioural Meeting, Minneapolis , USA, July 14, 2005

[Full text] [Abstract]



The purpose of this preliminary study was to reduce the stress of police dogs during a training course with the use of dog appeasing pheromones (DAP), the DAP being released from a collar the dogs were wearing all the time.

After a family life with their owner (member of the police force) and basic education for one and a half year, police dogs are separated from their families and gathered at a dog training center to undergo with their owner two intensive training courses of 7 and 8 weeks (with a 3 to 6 weeks break) at the end of which they pass tests deciding on their future career. Several dogs may come back for more specialized training sessions. The dogs stay in kennels at the training centre during the week and go back to their families for the week-ends.

Dozens of previous training courses have shown that the dogs are stressed as witnessed by symptoms such as barking at night, insomnia, weight loss, diarrhea, salivation, loss of concentration, exhaustion, poor performance… The experience is also very stressful for the owners (police staff) who are trained with their dog and whose dog will be judged apt or inapt to continue as police dogs. The experience was stressful enough to trigger the Ministry of Interior Affairs and the Police Corp to mandate this preliminary experiment.


Materials and methods

The experimental setup was devised as a double blind placebo-controlled 4 week study; of nine police dogs undertaking the training course, five dogs were wearing DAP collars and 4 dogs were wearing placebo collars. As indicators of stress levels, weight, (salivary) cortisol and different physiological and psychological parameters were evaluated at the beginning, during and at the end of the trial.

The Ministry, Police officials and dog owners were informed of the experimenters’ expectations of reducing stress, and were educated on stress indicators.



Data analyses were made with the Mann-Whitney, the Wilcoxon and the Fisher-Yates tests, using the SPSS program. Nearly significant results were found for the weight loss in the placebo group (p=0,069 n=4) and significant results for the difference of saliva cortisol level between placebo and DAP groups in the second week (p=0,016), the placebo dogs showing cortisol elevation but not the DAP dogs. One dog in each group barked 10 minutes a few nights and one placebo dog was found panting several mornings, but overall the dogs slept amazingly peacefully, contrary to the best expectations. There was no significant difference in sleep quality and (lack of) vocalization between placebo and DAP dogs.



The sleep quality and lack of nocturnal vocalizing caught our attention. The reduction of barking and insomnia at night was expected somewhat in DAP dogs, but not at all in the placebo dogs. And a high quality of sleep was not expected at all and never documented in the 15 years this facility was run (two to three times a year). There were always sleep problems linked to barking at night and the trainers even had to use anti-barking collars to reduce the problem. One dog was at the facility for the 3rd time and was well known as a relentless barker.

The tranquillity of (placebo and DAP) dogs at night is not easily explained. It made us think of the Hawthorne , Pygmalion and Experimenter effects. These effects can be measured in experimental designs but the rationale behind them is still speculative.

The Hawthorne effect is defined by Draper as “an experimental effect in the direction expected but not for the reason expected; i.e. a significant positive effect that turns out to have no causal basis in the theoretical motivation for the intervention, but is apparently due to the effect on the participants of knowing themselves to be studied in connection with the outcomes measured”. Owners and trainers were under observation and may have been subjected to the Hawthorne effect. The problem with the Hawthorne effect is that it is unpredictable and only observed a posteriori. “So as a methodological heuristic (that you should always think about this issue) it is useful, but as an exact predictor of effects, it is not: often there is no Hawthorne effect of any kind.” (Draper).

The Pygmalion (or Teacher) effect is a change in the performance from subjects in experimentation in the direction expected by the experimenter. Typically, said Draper, “if teachers were led to expect enhanced performance from some children, then they did indeed show that enhancement”. Even if not yet scientifically documented in animals, dogs might be submitted to the Pygmalion effect by their owners and trainers.

The Experimenter’s effects are positive or negative effects linked to expectations acquired consciously or not from the researcher (particularly in behavioural research). Prophesying an effect might create this effect or its opposite. Talking about the experimenters’ expectations to the police officials, dog owners and trainers may have influenced the outcome of the training results and the well being of the dogs. But nobody ever expected the effects to be better than the prophecy, as in this case.

Another possible effect could be related to a distant healing effect as significantly evidenced for example by Sicher and Targ in a triple-blind 6 months trial on human patients with end-stage AIDS (significant differences in favour of the treated group, healthier in every parameter from days in hospitalization, to new AIDS-defining illnesses, to improved mood, etc.). Healers included multiple philosophies and religions such as Christian, Lakota Sioux shaman, Qi Gong Master, Jewish Cabbalist, Buddhist, etc.; they were asked to hold an intention for the health and well-being of the patient for an hour a day, six days a week, for ten weeks (with alternate weeks off for rest), without the patient being aware he was submitted to this intention.

Having a focused intention for a patient to heal and be well already has significant effects on his well-being.

We are not trying to explain how (loving) intentions might work, just that they might have an effect on the health of a patient and that we should take this effect in consideration in experimental trials and, also, in therapy. This “Intention effect” may be part of the placebo effect. In science, we might not be interested to analyse the different components of the placebo effect and we may be just satisfied with the difference between the treated group and the placebo group. But in clinical practice, the placebo effect is part of the benefits the patient gets from the treatment; we may therefore have better results when we intend a patient to heal than when we do not believe in its healing. We still do not know how much of the therapeutic effect is due to the counsellor or to the conviction of the owner that the animal will improve, but we are now conscious it has an effect.



In conclusion, we cannot exclude the hypothesis that the beliefs of the experimenter may affect the results of experimentations and, by extrapolation in a clinical therapeutic approach, we might hypothesize that the beliefs of the counselor and of the owner might affect the results of the treatments. 



  • Draper SW 2005 (Feb 5) The Hawthorne effect and other expectancy effects: a note. [WWW document] URL (visited 2005 March 23)

  • Schroll S, Dehasse J 2005 The use of a DAP collar to reduce stress during training of police dogs, a preliminary study. Proceedings of the 5th International Veterinary Behavioural Meeting, Minneapolis , USA , July 14-16.

  • Sicher F, Targ E, Moore D, Smith H. A Randomized  Double-Blind Study of the Effect of Distant Healing in a Population With Advanced AIDS: report of a small scale study. Western Journal of Medicine, 168 (6): 356-363.


Key words

DAP, Healing, Intention, Stress 


© Dr Joël Dehasse - Behaviorist veterinarian - 05-12-11