Acquisition of the Token-Reward Habit in the Rat

Apparatus and procedure for establishing tokens as conditioned reinforcers in laboratory rats are described. Five rats were initially trained to deposit tokens (marbles) into a receptacle with each deposit response producing primary reinforcement. The rats then underwent discrimination training during which deposit responses were reinforced only in the presence of a clicker and localized illumination of the receptacle. Errorless performance was obtained within one to three sessions. The rats were next trained to press a lever in order to obtain the tokens from a dispenser. Initially, each lever-press response produced token delivery, and each token was immediately exchangeable for food. The schedules of token delivery were gradually increased to fixed-ratio and variable-interval schedules. Performance under these schedules was comparable to performance under similar schedules of primary reinforcement.

The Location of the Photoperiodic Receptors in the Aphid Megoura Viciae Buckton

1. The site of the photoperiodic receptors controlling the production of sexual and parthenogenetic females in the aphid Megoura has been identified by exposing adult apterae to supplementary periods of localized illumination. 2. The microilluminators devised for this purpose could be attached to the insects. In one type, the light beam was contained in a metal capillary; in another, light was conducted to the required site by means of a fine plastic filament. 3. Photosensitivity is confined to the head of the aphid, the central region of the dorsum being particularly important as a light pathway. The compound eyes are not involved, although stimulation of the eye by a relatively intense beam can elicit the response, probably because of light scattering. 4. The response is unimpaired if the eyes are covered with opaque paint, and often persists after they have been cauterized. 5. The photoperiodic mechanism in the embryo is actuated by light transmitted through the body wall of the parent. 6. The apparent absence of distinctive morphological features in the cuticle and epidermis of the dorsum suggests that the photoperiodic receptors are located in the underlying protocerebrum. Neurosecretory cells, possibly in the pars intercerebralis, may be implicated both as receptors and as humoral effectors.