Visual acuity in the pigeon.

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Abstract
Thresholds of minimum separable acuity of homing pigeons were detd. under various conditions of accommodation by training them to react to the direction of striae. The method used was a modification of the Lashley jumping technique. The birds were required to jump from a perch to 1 of 2 platforms behind which were placed the stimuli. These were horizontal and vertical lines separated by spaces of equal width on glass plates, and were illuminated by transmitted light. In a correct choice the bird was allowed to remain on the platform a few secs.; in an incorrect choice the platform gave way causing the bird to fall to a canvas net placed below. It was found that acuity was poorer at 30 cm. than at greater distances. 4 birds tested at various accommodation distances gave the following results when jumping distance was kept at 40 cm. or less: 30 cm., 3.3-7.8 min.; 40 cm., 2.7-5.2 min.; 60 cm., 3.3r4.2 min.; 100 cm., 3.2-3.5 min. Increase in jumping distance tends to produce an increase in threshold. Differences in acuity thresholds at various accommodation distances are not great in relation to individual differences and chance errors. Nevertheless, it seems likely that the near-point of accommodation has been approached or even passed at 40 cm.

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