Newly hatched domestic chicks were subjected to bilateral aspiration lesions of the anterior, dorsal, posterior or lateral regions of the forebrain and then were reared separately with one of two types of imprinting object. Between 3 and 10 days later they were tested for imprinting, pecking accuracy, visual looming and auditory startle responses. Lateral and dorsal lesion groups differed from a control group in the number of successful discriminations of their imprinting object and the lateral group was not significantly different from a random expectancy. All groups were impaired in pecking accuracy but the lateral group was the most severely affected. Looming responses and post startle freezing behaviour were reduced only in the posterior and dorsal groups which were also the least responsive in the imprinting tests. It was concluded that the lateral forebrain area is critically and specifically involved in the visual learning of imprinting being necessary for the discrimination of, but not for approach responsiveness to, imprinting objects.

Newly-hatched domestic chicks were reared separately with one of two types of imprinting object hanging in their cages. On the 5th day discrimination tests demonstrated strong preferences for the familiar object. On the 6th day the chicks were subjected to bilateral aspiration lesions of either the anterior or the lateral forebrain and their imprinting objects removed from the cage. Discrimination tests were made on the 9th and 12th days, the imprinting objects replaced, and a final relearning test given on the 14th day. The anterior lesion group was slightly impaired in the retention and relearning tests while the lateral lesion group was drastically affected, being significantly worse than the anterior group and with choices only just significantly above random expectation in the retention tests and no different from random choice in the relearning test. It was concluded that a lateral forebrain region is necessary for retention and relearning of a previously acquired imprinted preference.

No abstract

The purpose of this paper is to give a review of present-day welding in aircraft steel tubing construction. The various types of welding are discussed, together with a brief fundamental treatment of the welding process and its association with the hardenability and hardness of X4130 steel. The merits of preheating and postheat treatment are discussed.The second part of the paper deals with some considerations of the physical characteristics of steel tubing specially prepared with high proportional limits. The effect of welding on this material is also explained.

No abstract