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From: gary@ur-cvsvax.UUCP (Gary Sclar)
Newsgroups: net.pets
Subject: Re: Re: The six senses of a cat
Message-ID: <231@ur-cvsvax.UUCP>
Date: Thu, 10-Oct-85 10:17:45 EDT
Article-I.D.: ur-cvsva.231
Posted: Thu Oct 10 10:17:45 1985
Date-Received: Mon, 14-Oct-85 04:05:55 EDT
References: <160@cadsys.UUCP> <4371@alice.UUCP> <612@tellab1.UUCP>
Distribution: net
Organization: Center for Visual Science, U. of Rochester
Lines: 93

> In article <4371@alice.UUCP> ark@alice.UucP (Andrew Koenig) writes:
> >>  I read in net.bizarre that cats are
> >> deaf and partly blind - in the sense that they cannot hear and that they
> >> cannot see stationary things.
> >
> >I don't believe that cats cannot see stationary things -- if so, they
> >would bump into things.
> 
> True, cats can see stationary things. However, they rely on the detection of
> movement more than primates (like us) do.
> 
> Primates have stereoscopic vision. This means that their eyes work in close
> coordination to produce a three dimensional image. Other animals do not have
> much in the way of depth perception, though many of them do have higher powers
> of sight, in other areas, than primates. For example, dogs can see much better
> in low light than we can.
> 
> So, this lack of depth perception in animals other than primates means that
> they sometimes find it difficult to distinguish a stationary object from its
> surroundings, but have no such difficulty when it is moving.
> 
> Of course, most mammals (again, excluding primates) do not have color vision.
> This adds to this difficulty in seeing stationary objects, in that being able
> to distinguish colors would help to distinguish objects from surroundings.
> 
> For example, if a red ball is laying among green bushes, being able to
> distinguish between red and green would help you see the ball. If, however,
> both colors appear to you as grey, it would be harder to see the ball among
> the bushes, since you would be relying on shape alone to make the distinction
> between the ball and the bushes around it.
> 
> Thought ya might like ta know.
> 
> 
> 				       Barth Richards
> 				       Tellabs, Inc.
> 				       Lisle, IL
> 
> 				       "Ford, do you realize that robot
> 					can hum like Pink Floyd?"
>                                        -Arthur Dent
> 
> p.s. ALWAYS take what you read in net.bizarre with a pound of salt.


1) cats can clearly see stationary objects; we know because cells in the
cats visual system (at least some of them) respond to standing (stationary)
contrasts; there are many cells, however, that seem specialized to detect
moving stimuli, especially things moving at high speeds; neurophysiologists
(like me)
refer to these, for a variety of reasons, as "Y" cells

2) cats do make eye movements, but not of the same amplitude or frequency
as those made by humans; rather they prefer to fixate an object by moving
their heads

3) cats possess excellent depth perception; do you think they'd be able to
jump off high shelves and stuff and not kill themselves without it? roughly
90 % of the cells in the cat's visual cortex normal receive and combine
inputs from the two eyes and almost all of these, one way or another, are
sensitive to binocular disparities (ie- the differences in the images
received by the two eyes from objects at different distances and directions
relative to the observer); the ability to perceive depth is a
characteristic of all predator animals, not just primates, and the hallmark
of this ability are the forward facing eyes of they possess; things like
rabbits, which aren't predators, don't have this; other things, which are
not mammals but are predators do (owls falcons eagles)

4) cats do see better in the dark then we do; the cat retina is based,
primarily, on a type of photoreceptor specially engineered for sensitivity
in the dark; these are called rods; we also have them, but rely more on the
other type (cones); cats also have some cones, but a much smaller
percentage; also, it is thought that cats only have, at best 2 kinds of
cones; 3 {blue, green and red}
are required for full blow trichromatic color vision; cats have
some ability to distinguish colors, but much poorer then our own; other cat
specializations for night vision a) their pupils are much larger then ours
and the special shape also helps- admits more light, 
b) the front surface of their eyes have
much more light gathering power c)they have a reflective layer in the back
of the eye (called the tapetum) that gives light a second chance to pass
through the photoreceptors

5) cat vision is poorer then our own in the sense that it is not as acute-
they can't see things with as fine a grain as we can; in other words the
cats world would look, i think, slightly out of focus to us; but its fine
for them; being closer to the ground they dont have to see things as far
away as we do; their vision is scaled to their needs- things that are
closer subtend a larger visual angle, so vision need not be so acute

 g. sclar @ Center for Visual Science; University of rochester

	{decvax,seismo, other!rochester!ur-cvsvax!gary}