No abstract

The reinforcing event is present aa a stimulus in the situation in which a response is acquired and is absent from the extinction situation. When extinction conditions are made more similar to those of acquisition by introducing the reinforcer unrelated to behaviour ('free' reinforcement), the extinguished response is restored. Experiments with students, pigeons, and rats are described; and an analysis of the stimulus effects of reinforcement is used to account for 'dieinhibition', ' spontaneous recovery', and speedy reconditioning after extinction.

Presented herein is a method of including density fluctuations in the equations of turbulent transport. Results of a numerical analysis indicate that the method may be used to predict heat transfer for the case of near-critical para-hydrogen in turbulent upflow inside vertical tubes. Wall temperatures, heat transfer coefficients, and velocities obtained by coupling the equations of turbulent momentum and heat transfer with a perturbed equation of state show good agreement with experiments for inlet reduced pressures of 1.28–5.83.

Blindfolded subjects moved a stylus held in the hand over a standard distance of 4.5 ins. in a given direction. They then attempted to move the same distance in a direction at right angles to the first. Eight combinations of movements were investigated. The results reveal an illusion such that the extent of movements to left or right across the body is underestimated, while the extent of movements towards or away from the body in the mid-line is overestimated. The illusion applies to speed as well as extent of movement. Movement up or down in a vertical plane is equivalent to movement towards or away from the body in a horizontal plane. The interaction of this illusion with the well-known horizontal-vertical illusion of visual perception explains a failure to find any net illusory effect where lines visually displayed in different orientations were matched for length by unseen movements in similar orientations. Whether the visual and movement illusions simply co-exist or whether they are functionally related is not yet clear.

Subjects who were instructed to form images, and control subjects, were allowed an average of 3 sec./word in Expt. I and 6 sec./word in Expt. I1 t o study a mixed list of 50 high I and 50 low I nouns. Recognition was tested upon a list containing the old words mixed with an equal Psychol. 75, 513-519. verb. Behav. 9, 529-533. Learning and Memory. NewYork: Wiley. quency. J . exp. Psychol. 61, 23-29. responses. J . exp. Psychol. 83, 244-248.similarity on recall and recognition.