Some aspects of visual discrimination in the golden hamster

Abstract

This research was concerned with visual discrimination in the golden hamster. Relevant literature on the rat suggests that discrimination of simple geometrical shapes is determined by the isolation of a distinctive figural element; this is normally the base line. Learning of solid shapes is transferred to outlines and size alterations, but not to rotated figures and figure-ground brightness reversals. Some of these results may be experimental artifacts produced by the technique of investigation, in which the main flaws appear to be the use of large figures and a fixed choice distance. In the series of experiments reported here on form discrimination in the golden hamster, techniques were developed to meet these criticisms. The major experiment of this series indicated that golden hamsters were able to learn a brightness discrimination rapidly. Form discrimination of a triangle from a circle was more difficult and learning slow. However, all animals achieved discrimination scores above the 0.01 level of significance. Transfer tests showed that, as with rats, the response was to the positive figure and not to the negative.Generalisation extended to rotated figures, to both the tops and bases of figures, and to all alterations in size except the smallest (0.25 cms.); a behavioural measure of visual acuity had evidently been reached at this point. The results indicated that the animals were responding to the figure as a whole rather than to its parts. A complete breakdown in discrimination occurred when the figure-ground brightness relationship was reversed. A subsidiary experiment showed that hamsters were capable of perceiving depth. The results obtained on rotated figures and the parts of figures suggest either that form discrimination in the golden hamster is substantially different from that in the rat, or that they are due to the smaller figures used and the freedom of scrutiny allowed.