Can not see vertical lines. And vice-versa. Whether or not they want to. If food is placed on the opposite side of a surface with vertical lines the cat will 'see' nothing but empty space and will not try to get the food (if it is too far to jump).
first online source I could find to back this up - http://jn.physiology.org/content/41/4/896.abstract
Otherwise the book 'The Three-Pound Universe' explains this phenomenon well.
Daily Paul cured my abibliophobia.
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