Monday, August 17, 2009

Dogs especially good at interpreting cues from people

In light of recent critiques of Fort Bend Deputy Keith Pikett's "scent lineups" using bloodhounds, I was interested to see this USA Today story about dogs' ability to pick up subtle cues from their handlers:
"Dogs evolved with humans, and a number of studies have suggested they are particularly sensitive to human cues," says psychologist William Roberts of Canada's Dalhousie University. Sentimental pet owners might even say their dogs know what they are thinking.
The story brings to mind an example raised by a reader in response to an earlier post: Clever Hans, a German horse from a century ago who was famously believed to be able to perform arithmetic. After extensive testing, it was determined that his trainer needn't participate for the horse to perform its trick, ruling out fraud, but that "the horse got the right answer only when the questioner knew what the answer was, and the horse could see the questioner," according to the Wikipedia entry. In other words, subtle cues about human expectations were giving away the answer, but the horse couldn't independently discover it.

My suspicion is that the same thing may also occur with Deputy Pikett's "scent lineups," which have recently generated provably false accusations that resulted in ongoing civil suits. Dogs take no oath of honesty and have no understanding of their role in the legal system. Many sniffer dogs have high error rates. To the dog this is a game - a trick performed to earn a reward. But since Rover can't sit in the witness box and tell us what he smelled, the courts have allowed dog handlers to interpret for them, ignoring the strong possibility that the dog is only telling their trainer what they want to hear.

6 comments:

Anonymous said...

No doubt dogs can pick up on cues from their owner/handler. But my understanding is that in a scent lineup, the dog's handler does not know which of 6 cans the evidence scent is in.

So if that is the case, how then could the handler cue the dog to hit on, say, Can 4, when the handler doesn't know that Can 4 holds the suspect's scent?

I'm just askin'.....

Gritsforbreakfast said...

The Clever Hans example shows that animals can cue off anybody in the room, not just the trainer. My understanding is that even if Pikett isn't told which can the evidence is in, typically prosecutors or others involved in the case are present to witness the lineups. If ANYBODY present knows which one is the evidence, that could taint the outcome.

Anonymous said...

Testimony (evidence) from a dog is questionable on its face. Although a lot of thinks done by the Criminal Justice (or shoul I say "injustice") System in Texas are questionable. Maybe the surprise in all of this is we are surprised that the scent line-up has been take seriously.

Inky said...

Hey if the dog in a scent lineup cues off the guilty guy that he is the guilty one then its not all bad.

What we need here is a water witch!

Mike Howard said...

This is yet another example of the criminal justice system lagging far behind science/medicine. How the criminal justice system intersects with mental health bares little resemblance to current medical/psych thought. Eye witness identification has been shown (by Elizabeth Loftus another many others) to be highly faulty. Intoxalyzer/breathalyzer machines have been shown to have problems. Standardized field sobriety tests are shaky. Fingerprints are anything but scientific. And common sense should tell you that dog scent evidence is not reliable enough for he high bar needed to take away someone's liberty. But all these methods are used to establish guilt in the system. IMO all this is symptomatic of a much bigger problem in the system: while our country was built upon the presumption of innocence, burden of proof, and beyond reasonable doubt standards, most Americans are squeamish about where that leads. I am daily shocked when reading the comments sections in the newspapers at how reactionary and "kill 'em all and let God sort it out" the majority of Americans are. As long as that feeling exists in the majority of Americans, they will elect similarly minded politicians who will enact laws that will continue to erode our liberties.

Simon said...

1. William Roberts is not Faculty at Dalhousie University. Mark Petter, a former student of Roberts is currently doing his Ph.D at Dal.
2. Double-blind procedures take care of the Clever Hans effect. We use them in my lab all the time.

Simon Gadbois