
Handler beliefs affect scent detection dog outcomes (2011) - ColanR
https://link.springer.com/article/10.1007%2Fs10071-010-0373-2
======
daddylonglegs
Dogs are very good at reading people and if the handler wants an indication
they will get it; they may not even realise that they're influencing the dogs.
As others have said, this has been known for a long, long time. There was even
a book written taking a wry look a scent dogs (and the plans for scent bees
etc that were in vogue during the great war on terror) [1].

That said, dogs can be fantastic when used for finding threats rather than
'proving' what the handler already believes. They have a combination of nose
and brain that we can't replicate any other way and are great for search and
rescue, finding explosives and some law enforcement searching.

[1] [https://headspace-the-book.blogspot.com/2008/07/acpo-
police-...](https://headspace-the-book.blogspot.com/2008/07/acpo-police-dog-
training-and-care.html)

~~~
sneak
...and yet dog alerts (encapsulating handler biases) alone are still used to
establish probable cause in the US to strip people of their rights to privacy,
and has resulted in jail for thousands of people who do not deserve it.

~~~
dymk
It's better than absolutely no preventative measures at all

~~~
ksdale
That's very debatable. I, personally, would much rather that people in
possession of drugs go free rather than the police using the dogs as an excuse
to search people they don't like the look of.

~~~
Smithalicious
Yes, but I suspect you would also support lighter sentencing or even
decriminalization of drugs. I don't think you'd think the same if it was
concerned potential terrorists or child sexual abusers.

Basically, this kind of comment usually encodes some belief on what the law
should be rather than a belief about how it should be enforced. And that's
just not the issue at hand here.

~~~
ksdale
You're correct about how I feel about drugs, but I think the general argument
applies across the board. There are times that enforcement costs are too high,
given the crimes they prevent.

One of the most common criticisms of airport security in the US is that the
harm it is preventing is nowhere near commensurate with the burden it imposes
on the populace. That may or may not be true, but it's not a belief about what
the law should be, it's a belief that at some point, the price paid for
additional safety is too high.

Likewise with children, as a father of 4, I also understand the desire to go
to any lengths to keep our children safe, but keeping them in a bubble for
their entire lives, while certainly protecting them from many tangible harms,
will ultimately stunt their growth. Once again, the price paid for safety can
be too high.

I happen to think that drug sniffing dogs are on the wrong side of the line.
They probably do alert the police to drugs that would not have been found
otherwise, but in my opinion, they allow the police to have far too much
latitude when it comes to searches.

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seanwilson
Is this not fairly well understood? e.g.

[https://en.wikipedia.org/wiki/Clever_Hans](https://en.wikipedia.org/wiki/Clever_Hans)

> Clever Hans (in German: der Kluge Hans) was an Orlov Trotter horse that was
> claimed to have performed arithmetic and other intellectual tasks.

> After a formal investigation in 1907, psychologist Oskar Pfungst
> demonstrated that the horse was not actually performing these mental tasks,
> but was watching the reactions of his trainer. He discovered this artifact
> in the research methodology, wherein the horse was responding directly to
> involuntary cues in the body language of the human trainer, who had the
> faculties to solve each problem. The trainer was entirely unaware that he
> was providing such cues.

~~~
edoo
It should be easy to train the dogs in an environment where the trainer does
not know the intended result and must investigate each claim from the dog. All
the dog training vids I've seen have the trainer themselves knowing exactly
what lies in the course.

~~~
silveroriole
I don’t think this would be easy. For training, the reward needs to come as
quickly after/during the action as possible. Most dogs don’t have a great
mental capacity for figuring out that they’re being rewarded for something
that isn’t happening right now. If the dog has to wait even 10 seconds for the
trainer to figure out whether to reward or not, a lot of dogs are going to get
confused.

~~~
logfromblammo
During training/testing a second person, who is not visible, audible, or
smellable to the dog, and who knows the conditions of the course, observes the
pair via cameras and microphones.

When the dog hits on something, the observer presses a button, indicating
which target or decoy was indicated, or that an unexpected other object was
indicated. The observer may also indicate when the dog seems distracted, or
especially attentive to the handler.

A computer takes the buttons as inputs, and if its intermittent reinforcement
program indicates it, the handler receives an instruction to reward the dog.
The program may also reward the dog for misses, or just for paying attention
to handler instructions, so the handler is not able to associate rewards with
accurate hits. The handler then still has to investigate the hit to determine
what the dog found.

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praptak
I've heard this mentioned a few years ago in a TV report on dogs used in labs
that test evidence for criminal trials. Their procedure was to let the dog
_alone_ into a special scent-free room that contained the sample being tested,
plus a few control ones. The samples were placed into containers that only let
the smell out (no visual cues, even though the samples were identical-looking
cotton swabs).

Also, I vaguely remember a high-profile case where the evidence was dismissed
precisely because the procedures for gathering and testing the samples were
not followed.

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praptak
In this context it is ridiculous that a dog test is considered a probable
cause for a police search: news.ycombinator.com/item?id=10942196

~~~
Smithalicious
Is it really? Probable cause doesn't need to be a high bar, in my opinion.
Contrary to what people here seem to think, I don't think a police search is
_that_ invasive and I'd rather we perhaps search some people on shaky grounds
than we let people with drugs/bombs/whatever walk free.

~~~
htek
So you're cool with a cop that is biased against black people using their dog
as a pretense to search them? Oh, and, yes, a police search is invasive and
demeaning. I suggest you try it before you discount it.

~~~
Smithalicious
No I do not support people doing bad things. That does not mean that I am
against everything that could possibly be used for evil. This is an absolutely
inane accusation.

Are you fine with black communities being ruined by crack cocaine because
police can't search people? Of course not, that'd be a ridiculous thing to
think.

~~~
htek
What you're saying is that it's okay to treat all black people as if they're
criminals because a small subset of them engage in criminal activity. It is
well established that black and white people use illegal drugs at about the
same rate. Where's the call for stop-and-frisk of all white people? Or doesn't
that fit your think-of-the-black-community veil over your racism?

------
ptah
does this imply that the dogs perform a similar role to dowsing rods in this
situation?

~~~
693471
This is the analogy I've been looking for.

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the-dude
Up to 2006 'scent identification' ( linking persons to objects ) was used as
evidence in Dutch courts.

It turned out the test weren't done 'blind' and the practice has been
abolished.

------
tiku
Well it is not far fetched that they can smell the excitement or anxiety of
their owners as they approach the evidence they believe is the correct one?

~~~
anon9001
> For scent detection dog handlers, beliefs that scent is present might result
> in either sufficient inadvertent postural and facial cues so that dogs will
> respond regardless of the absence of scent

I don't know how good dogs are at pose detection, but it's definitely
plausible that they can tell when an alert is expected.

~~~
bayesian_horse
A less subtle cue would be how they treat the "suspect".

It's less about the handler's pheromones and more about movement, speech and
posture.

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tanepiper
I've been doing detection classes with our Polish Hunting Spaniel and she's
quite the natural, but the hardest part of it is training the human (i.e. me)
to NOT give off any queues about where I think things may be.

Of course, these are fun classes and in no way controlled environments - but
the best thing you can do is to trust the dog's judgement.

------
your-nanny
I think the more likely explanation is that the handler's sensitivity to dog
alerts changes with handler's beliefs, a possibility they raise in the paper's
discussion.

------
mgarfias
would have been better to use SAR dogs.

------
truths33k3r
how is this nonsense even getting published?

tiny sample size, n=18 dogs 5 different breeds of dogs large variance of dog
age

~~~
BlackFly
This shouldn't surprise you, but if the effect is large and real, you don't
need large sample sizes to prove something. As an example, a loaded die that
always comes up with 6. After 18 straight 6's in a row, you are more than
assured that you have a loaded die. I imagine that a rational person is
convinced long before the 18th 6.

The point is: large samples are only needed to measure small effects. Most
studies nowadays need large samples because the large effects are low hanging
fruit and were noticed quickly (in the past). Meanwhile, finding a single
black swan proves that not all swans are white.

This study proves that in even a small selection of scent dogs, you are going
to have dogs which are highly affected by handler signals. You might be able
to use the methods of the paper to exclude dogs which pick up on handler
signals and therefore improve the training regimen of scent dogs, there is no
evidence to support this possibility however.

------
corodra
18 dog teams? What a thorough experiment. Sounds like the infamous chocolate
weight loss study that was pushed to the media that made them look stupid.

To a small degree I can agree to this. But I have k9 officer friends and I
know their dogs. Good luck with this. It means a bad and impatient handler
rather than an ineffective dog. But it's alright, police baaaaad. Evidence is
evil.

------
jaclaz
The observation seems logical, but I wonder what is actually the relevance of
the study in practice.

I mean, there are three common situations where these dogs are used:

1) airports, stations, traffic stops etc. where the influence of the trainer
might be relevant (i.e. the trainer, even if involuntarily, may influence the
dog if the person that is sniffed - or their belongings/looks/behaviours/etc.
- look suspicuous to the trainer)

2) search in buildings for drugs or explosives

3) screening of mail, packages, containers, etc.

I believe that among these only in activity #1 the trainer might have some
pre-constituted suspect that would "trigger" the influence on the dog.

But in any case the dogs are only used as a means of "triage" of sorts, so at
the most this influence leading to false positives will cause some time
wasted.

Still in case #1 (and possibly in case #3) the issue might be that if there
are too many of these false positives, while the attention of the
trainers/policemen is drawn to the "false target" some other one (actually
carrying drugs or explosives) will "go through".

~~~
bayesian_horse
I have heard the term "search warrant on four legs".

In many jurisdictions, including the US, police officers are not allowed to
search anybody or their cars, even if they are black.

So if the dog learns to please his handler by indicating contraband, they have
a chance to at best inconvenience anyone they (dis)like.

~~~
jaclaz
>So if the dog learns to please his handler by indicating contraband, they
have a chance to at best inconvenience anyone they (dis)like.

Sure, but (of course it depends on countries and local Laws) it is only one of
the possible ways (excuses) that can be used to target someone.

Of course if in the car there is no drugs (or explosives) the only net result
is a waste of time of both the policemen and the "target".

It would seem to me much more relevant to know how many cars searched after a
dog sniffed something ended up as being actually contraband free (false
positives) and how many actually turned out as actually containing some drugs
or whatever.

If the dogs (in experiments without the influence of the trainer) have an
accuracy of - say - 90% and with the influence of the trainer (or whatever
other reason causes on field differences) this drops to - still say - 55% then
there will be an issue as we would be nearing the flipism convenience, but if
the overall accuracy remains in the 80 or 85% range then the effect - even if
noticeable - would be not much relevant in practice.

Or, if you prefer, I completely agree that a trainer can induce a dog to sniff
something even when there isn't any, but the relevance of the fact depends
only on how often this happens.

~~~
cbanek
For less reputable police, they might just say the dog alerted when it didn't.
What's a layman to say? No it didn't? And courts usually give the benefit of
the doubt to police, even if they technically shouldn't. Because police don't
need probable cause to use a dog to search your car means it is the de facto
way to escalate to a probable cause search, and even if a dog isn't present,
bringing one there usually makes people uneasy, leading to claims of
"suspicious behavior", and allows the police to detain someone until it
arrives.

Sadly, I don't think the false positive alert rate is something the police are
looking at or trying to reduce. In my cynical opinion, they are just looking
for more reasons to find you a criminal, even if you aren't one. If they view
you as a criminal to start, that's a huge burden to overcome.

~~~
jaclaz
>For less reputable police, they might just say the dog alerted when it
didn't. What's a layman to say? No it didn't?

Exactly.

~~~
whenchamenia
Odd, I raised that objection and a warrant to search my car was still issued.
There are many, many shady cops. My guilt had alredy been assumed, and they
were just hunting for justification.

