Re: Object Constancy

From: Harnad, Stevan (
Date: Thu May 01 1997 - 17:06:00 BST

> From: Minnett-Westwood, Della <>
> > > > (16) Object Constancy is:
> > > > A. *seeing something as the same whether near or far
> > > > C. seeing something as the same whether big or small
> > >
> > > I took C. to mean "seeing something as the same whether it's image on
> > > your retina is big or small" ie. a blow-up of a picture to A3 being the
> > > same as the original on A4, or whatever. It's a bit confusing. Why is
> > > C. wrong?
> >
> > Because object constancy is about seeing something as the same THING
> > whether near or far, upside down or right-side up, rotated or unrotated,
> > etc.
> >
> > Seeing a shape as the same shape whether bigger or small is not object
> > constancy (and actually we would not speak about it as a constancy at
> > all), because a big thing and a little thing, even if their shape is the
> > same, is not the same thing. They're only the same KIND or thing (or,
> > better, the same SHAPE, but not the same thing).
> Surely A and C are both right? For instance, you see that Big Ben is
> Big Ben whether you are standing right next to it
> (i.e. near) or if you are looking across the Thames at it (i.e. far).
> Therefore A is right. But when you are standing next to it, Big Ben
> looks pretty big, because it is near, and from across the Thames it
> looks smaller, because it is further away. But you still recognise it
> as Big Ben. Surely C and A are linked - if something is far away then
> it is small, and if it is near then it is big?

They're only linked in that the size of the retinal projection is the
same: small when the object is small, or far; large when the object is
big, or near. But as an object approaches us from a distance, we do not
see it as growing, we see it as coming closer (and staying the same
size)! And that constancy is COMPLETELY inpenetrable cognitively. The
only way you can see it as growing as it comes near is if you eliminate
all depth cues (say, you use a lit sphere in the dark: then you will
see it as growing rather than remaining constant in size and coming

Big Ben doesn't swell as you move towards it: it looks the same size,
but nearer, and that's exactly what object constancy is!

> > Here are two events that will cast exactly the same "shadow" on your
> > retina: (1) a faraway sphere, moving closer and closer; (2)
> > a small sphere, growing bigger and bigger. You would see the first thing
> > as being the same size, despite the growth of its shadow on your retina,
> > but you would see the second thing as growing (and that's not a
> > constancy!).
> I know that (2) is not a constancy as it is changing from a small
> sphere to a big sphere, but so is (1) - I'm afraid I don't agree that I
> would see (1) as being the same size, because my image of it would be
> growing. However, I would be able to recognise it as the same thing.
> This is very confusing!! Minnett-Westwood, Della.

Actually, the remarkable thing is that although the shadow on the retina
grows and shrinks in both cases, we do not see it as growing and
shrinking but as moving nearer and further in one case, but not the

This archive was generated by hypermail 2b30 : Tue Feb 13 2001 - 16:23:52 GMT