SOME ELECTRONIC CONTROL UNITS FOR OPERANT BEHAVIORSTUDIES: II. A RANDOM RATIO GENERATOR'

W. N. SCHOENFELD, W. W. CUMMING, A. G. SNAPPER,and P. HAAS

COLUMBIA UNIVERSITY

We present below an apparatus used in our laboratory, in conjunction with the translatordescribed in an earlier note (Schoenfeld et al., 1960), for generating programs of randomratio reinforcement.The general principle underlying the operation of this generator involves a high fre-

quency pulse, the duration of which is manipulable (without changes in the frequency). Thismakes possible a temporally defined reinforcement schedule with the tD + t1A cycle madevery short with respect to the minimal inter-response time of the organism. The coincidenceof response with tD yields reinforcement, and the probability of this coincidence is definedby the ratio tD/(tD + tI) because of the small values of the time parameters in-volved (see also Brandauer, 1958). The properties of ratio schedules generated in this wayinclude: (a) equal probability of reinforcement for each response; and, (b) independence ofthe probability of reinforcement (coincidence) and inter-response time.The circuit diagram of the random ratio generator is given in Fig. 1, which is accom-

panied by an index of components. The operation of this circuit may be traced as follows:(1) A 100 cps wave is squared (E,) and sent to a flip-flop (E2) for frequency division

by two. In our laboratory, we have used the 100 cps output of a Hewlett-Packard secondaryfrequency standard, but both the frequency and the source may be varied without sub-stantial change in the circuit. As divided by E2, 50 complete cycles per second are avail-able, each constituting a tD + tA cycle with tD occurring at the beginning ofeach cycle and continuously variable from less than 10 microseconds up to the full cyclelength of 20,000 microseconds.

(2) The output of E2 passes through a pulse amplifier (E3) giving an 80 volt negativepulse of 50 microseconds' duration for each input pulse. The output of the amplifier is fedto: (a) an additional amplifier (involving tubes T4 and T5), and thence to the translatorearlier described, where it initiates fD; (b) a phantastron circuit.

(3) The phantastron (E4) and its related components operate to produce a delayed outputby generating a positive gate. The duration of this gate is variable by means of C3 and R2,the output being finally used (after differentiation) for the initiation of tj.

(4) Operation ot this random ratio generator requires a well-regulated power supply.When desired, calibration by a high quality oscilloscope against a standard time base willgive a high degree of precision.

Calibrated delay generators of good quality are commercially available and may be sub-stituted for the phantastron circuit used here.

REFERENCES

Brandauer, C. M., The effects of uniform probabilities of reinforcement upon the response rate of the pigeon.Unpublished doctor's dissertation, Columbia University, 1958.

Schoenfeld, W. N., et al., Some electronic control units for operant behavior studies: 1. A response and reinforce-ment contingency translator, J. exp. anal. Behav., 1960, 3, 17-20.

'This apparatus was developed in conjunction with research supported by the National Science Foundationunder Grants G-3408, G-5517, and G-8671.

Received December 1, 1959

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SCHOENFELD, CUMMING, SNAPPER, and HAAS

Figure 1. Circuit diagram of the random ratio generator. The outputs, labeled tD and t A are negative pulsesof 180 volts (at an impedance of approximately 47 K ohms); these pulses are of approximately 50 microseconds'duration, with rise time less than 3 microseconds.

INDEX

C,-0.001 mf., 400 v.

C2-0.01 mf.,400v.C3-variable, 22 mmf. to 0.001 mf., 400 v.

C4-0.02 mf., 400 v.

C5-0.l mf., 400 v.

C6-0.1 mf.,400v.C7-0.02 mf., 400 v.

C8-0. I mf., 400 v.

C9-0.1 mf., 400 v.

E,-EECO squaring circuit Z-90001*E2-EECO flip-flop Z-8342*E3-EECO pulse amplifier Z-8489*E4-EECO phantastron Z-8771 *E5-EECO pulse amplifier Z-8489*B+ = +200v. D.C.

R,- I megohm, 0.5 wattR2-0.47 to 3 megohm (variable), 0.5 wattR3-l00Kohm,0.5 wattR4-3.3 K ohm, 0.5 wattRs- I megohm, 0.5 wattR6-47 K ohm, 0.5 wattR7-100 K ohm, 0.5 wattR8-3.3 K ohm, 0.S wattR9_- megohm, 0.5 watt

R1o-47 K ohm, 0.5 watt

T,-6AL5 tubeT2-one-half 5963 tubeT.-one-half 5963 tubeT4-one-half 5963 tubeT5 one-half 5963 tube

*All EECO plug-in circuits are manufactured and sold by the Engineered Electronics Co., 506 East First Street,Santa Ana, California.

a +

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