People With Capgras Recognize The Faces Of Their Own Family

Yet They Say Those Relatives Are Impostors

They Have Plenty Of Evidence That It Is The Same Person

The Belief Is Still Accepted As True

In Lab Tests A Parent's Photo Got The Same Reaction As A Stranger's

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OKAY BACK FROM THE TESTING ROOM 🧪

Five People Believed Someone Close To Them Had Been Replaced

People With Capgras Say The Impostor Looks Almost Identical

Researchers Measured How These Five Reacted To Faces

They Used A Measure Called Skin Conductance

Sensors On The Skin Record The Activity Of Sweat Glands

Two Of The Researchers Had Made A Prediction In 1990

They Suggested Capgras Comes From Damage In The Brain

The Damaged System Would Be One That Responds To Faces That Matter

If So These Patients Would Respond Weakly To Familiar Faces

The Team Set Out To Test That Prediction

Five Members Of The General Public Took The Same Test

So Did Five Psychiatric Patients On Similar Antipsychotic Drugs

The Researchers Also Played All Of Them A Series Of Tones

Those With Capgras Reacted Normally To That Sound

Their Reaction Also Faded At A Normal Rate As The Tones Repeated

With Faces The Results Were Different

Only The Faces Failed To Trigger A Normal Skin Response

A Familiar Face Produced The Same Skin Reading As A Stranger's

A Man Was Shown The Faces Of His Own Family

He Could Not Say Who A Single One Of Them Was

His Condition Was Prosopagnosia Which Is Also Called Face Blindness

He Was Also Shown The Faces Of Famous People

Every Face In The Test Belonged To Someone Familiar

The Famous Faces Were Just As Unknown To Him

A Researcher Named Bauer Gave Him Five Names Per Face

One Of The Five Names Was Correct

His Guesses Were No Better Than Chance

Sensors Recorded His Skin Conductance The Whole Time

His Skin Responses Were Far More Accurate Than His Guesses

Bauer Wrote That This Suggested He Recognized The Faces Physically

Bauer's Paper Proposed Links From Visual Areas To The Limbic System

The Method Was Based On The Guilty Knowledge Test

Bauer Said It Could Help Find Recognition Left After Brain Damage

This Man's Result Was The Reverse Of The Capgras Result

His Skin Reacted To Faces He Could Not Name

In Capgras People Recognize Faces Without That Skin Reaction

A Man With Capgras Accepted His Mother And Father On The Phone

In Person He Called Them Impostors

His Skin Reacted No More To His Parents' Photos Than To Strangers'

Three Other Researchers Asked Why Anyone Accepts A Belief Like That

They Split The Problem Into Two Questions

The First Is What Brought The Idea To Mind In The First Place

For Capgras The Weak Reaction To Faces Is One Proposed Cause

Their Second Question Is Why The Idea Is Accepted As True

Such A Belief Is Bizarre And Plenty Of Evidence Contradicts It

The Researchers Named A Second Factor To Explain That

It Is A Failure To Reject The Belief

In Their Account Both Problems Are Needed For A Delusion

A Weak Reaction To Faces Alone Would Not Be Enough

The Three Also Listed Five Difficulties With Their Own Account

They Tried To Deal With Each One

Their Two Factor Account Is Still A Proposal

They Applied It To Six Different Kinds Of Delusion

Beliefs Like These Are Seen In Schizophrenia Brain Injury And Dementia