Two predictions derived from the frequency theory of verbal discrimination (VD) learning were that both reduced percentage occurrence of reinforcing information (% ORI) and an increase in presentation rate would retard VD learning. A third prediction was that % ORI would interact with presentation rate, resulting in a greater retardation of VD learning at the faster rate under reduced %ORI. Three levels of % ORI (100%, 50%, and 2S% ORI) were combined factorially with two levels of presentation rate (2:1 and 2:4 sec.). Six independent groups of 15 college students each were used. All three predictions were confirmed.

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A simple, inexpensive, and reliable apparatus for photocell detection and amplification is described. The sensitivity, voltage and current amplification, and speed of this apparatus, make it well suited to application in latency measurement in animal mazes. The apparatus can be used in any sort of application where a resistive type of transducer is needed to trigger some other event at higher voltage and current levels than can be done directly by the transducer alone.Studies of animal learning in maze apparatus often use measures such as latencies or their derivatives, running speed, which depend upon the .sensing of the animal's movement through the maze in an unobtrusive manner. Typically, these measuring devices involve the use of a photocell. Among the features of the photocell detector described here are: high-input impedence, enable function, reset/disable function, sequential operation, high-current ou tput for driving solenoids or relays, single power supply operation, and simplicity of construction. The apparatus can be built for under $50, including all parts.to the comparators has a common collector transistor configuration and therefore a very high resistance. This makes the inputs capable of detecting low-current photocell signals without appreciably influencing the signals. The outputs of the comparators are connected to a flip-flop (F-F) which provides a memory. The output transistor is capable of handling currents up to 200 rnA. The device then, serves the following functions: voltage sensing, memory, wave shaping, and current amplification. The specified range of operation is from 5 to 18 V.The basic photocell detector is made by forming a

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