Is this a real psychological disorder? (Copying of another person's movements)

This is for a short story I’m writing. In the story, one of the characters starts to copy the movements of her older sister, such as only eating when she does (and the same foods/amount of food), doing what she does when she does it (if sis is reading a book, she has to also), buying things that are the same or equivalent to things sis buys. She starts semi-stalking her (they live in the same house, so it’s not really stalking) to find out what she’s doing, so she can do it too. When sis is away, she lies in a catatonic stupor. Eventually, something science-fictional happens and you find out why she’s really copying, but until then the characters are looking for an excuse that fits in with what we know now (the story is contemporary). Is there any diagnosed psychological disorder that would seem to fit? Or will I have to make one up? I’d rather use something real.

Thanks in advance!

Sounds like an unusual form of obsessive-compulsive disorder to me.

Yeah, I considered OCD, but since it’s not a standard compulsive behavior I didn’t know if it would fit. Also, it’s not clear she’s doing this because of anxiety–the story isn’t from the copier’s VP, so as far as the rest of the family is concerned, it’s a mystery. Maybe it would be best to keep it a little vague and not co-opt a real disorder, if I can’t find one that fits exactly.

Thanks for linking that article, though, since I just learned a new word from it–clinomorphism. That one’s going to come in handy someday.

That sounds somewhat like autism. Pathological demand avoidance syndrome also fits a bit.

An analysis was made, distinguishing features which all 21 children in this first cohort shared from those which were frequent but not invariable.1,2 Some which were expected to be merely background features turned out to be held in common more than we had realised: notably symbolic play (especially doll play and role play), and at least “soft” neurological signs. The central salient characteristic of all 21, which made them strikingly difficult for their parents and teachers, was an obsessional avoidance of the ordinary demands of life coupled with a degree of sociability that allowed social manipulation as a major skill. Despite our reluctance to use the word “manipulative” in speaking of children, it was impossible not to recognise this shared quality, especially as it contrasted so clearly with autistic children.

Comfortable in role play and pretending
Still more interesting is the robustness of this feature as it survives in adulthood; only three of the 18 adults in study C did not show any of the nine types of fantasy activity listed in the survey, and all of these were male. Five showed six or more types. Ten seemed to lose touch with reality through fantasy. Seven mimicked other people’s roles from video, and seven from real life; four mimicked odd or violent behaviour. Of the “real life” role mimics, three took this to extremes so that it was “hard to know who she really is”. Seven put on an act within their own general identity, four acted out self generated stories or scripts, and four would actually record an act or role on video, audiotape, or photos in an obsessive manner. Six engaged in fantasy communications such as poison pen letters, fantasy love letters, hoax phone calls and letters, false accusations to the police, and obscene stories.

I know next to nothing about this, but my WAG would be a form of Tourette’s, based on reading something like this in Dr Oliver Sacks’ excellent book “The Man Who Mistook His Wife for a Hat”. I highly recommend the book to anyone with even a passing interest in neurology/clinical psychology. And anyone who knows more is free to dispute my suggestion.

The medical term for pathologically imitating other’s gestures is “echopraxia” (“echolalia” is repeating back what others say). You can google it to find out what disorders it’s associated with.

What you describe is a symptom, not a diagnosis of a particular disease itself. And that sort of symptom can be found in a number of diseases.

Postulate some sort of funky brain lesion if you like. Something in the basal ganglia, perhaps.

Okay, now that’s exactly the kind of word I needed! Something medical/scientific-sounding without being terribly specific and thus easily disproven. Oh, and that sounds kind of science fictional. Thanks!

It sound to me like a very common medical condition:

being a younger sibling.

And now you know the secret meaning behind the story!!! I may have to kill you.

Glad to help, but as QtM said, echopraxia wouldn’t be a diagnosis - it’s just a symptom. In other words a doctor wouldn’t say echopraxia “explains” imitating gestures - it’s just the medical term for it. So they’d still be looking for the reason why your character exhibited echopraxia - like a brain lesion as he suggested. Also I’m guessing that echopraxia is specific to motions - I have a feeling that complex behaviors like buying the same clothes wouldn’t fit. You should research it a bit.