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AN AUTOM ATIC SHOCKING-GRID APPARATUS FORCONTINUOUS USEB. F. SKINNER AN D S. L. CAMPBELL

Indiana UniversityReceived May 13, 1947

The usual shocking-grid consists of a series of bars w ired alternately to positiveand negative poles of the current source. The animal m ay avoid shock by stand-ing on like poles, or by shorting the grid with faeces. Constant attention isnecessary to prevent this, and the experiment must be disturbed from time totime. The apparatus here described w as designed to provide an escape-from-shock motive in connection with a lever-pressing response in rats, to permit th euse of automatic controlling and recording devices which require little or nosupervision.

In this apparatus a commutator provides a changing pattern of polarities atthe grid bars. Any two bars are of opposite poles at least once each second, andthe shorting of any one pair leaves all other pairs fu nct ion al part of the time.The grids are* also slowly rocked by an eccentric drive to clean them of faecesThe walls are part of the electrode system and the design insures equipote ntialpunishment throughout the box.The com mu tator may be seen at 2, figure I.1 Figure 2 gives a wiring diagram .The commutator consists of a hollow fiber cylinder, encircled by two metalbands. Brushes mak ing conta ct with these ban ds are wired to the secondarytransformer leads. Small brass conta cts are inserted into the cylinder in fourrows of twe lve each. Each row is wired within the cylinde r to the two bands togive a different pattern of polarities fo r each row. Twelve brushes carry ingcurrent from these con tacts are conn ected to the bars of the grid. There arethus four patterns of polarity at the grid bars during each revolution of thecommutator, and each bar is "hot" with every other bar at least once during arevolution. The co m m uta tor has a speed of 60 R.P.M.This device can be used with any of the standard sources of shocking curren t.In the model shown in figure 1, th e transformer has a secondary output of five-hun dred volts. Va riable resistors and a large fixed external resistance are inseries w ith the grid.The grids are slowly rocked through 90 degrees at the rate of 16 cycles perminute. A substitute for the eccentric drive might be a direct gear drive withfiber gears m eshing from one bar to the next, in which case the bars would makecomplete revolution s. In the appara tus sh ow n, the speed of the mo tor could bechanged with a variac in order to determine a suitable speed. The grid barsare connected with the commutator through brushes.The experimental box is similar to that which has previously been used withhunger and thirst drives (1). A seven-watt lam p is m oun ted over frosted glass1 B u i l t by Mr. Max Wastl , Lafay et te Ins t rum ent Co. , La fayet te , Indiana.

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306 B. F. S K I N N E R AND S. L. CAMPBELL

Fio. 1. E X P E R I M E N T A L Bo x AN D S H O C K I N G D E V I C E(1) t ransformer, mil l iammeter and variable resistor; (2 ) c ommut a t o r ; (3 ) motor fo rcommutator and eccentric drive; (4 ) variac fo r motor speed cont ro l ; (5 ) experimentalbox with rocking grids.

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F I G . 2. C I R C U I T D I A G R A M FOE S H O C K I N G D E V I C E(1 ) transformer (500 V., a.c . from secondary) ; (2 ) mil l iammeter ; (3 ) adjustable resistor(2-6 meg ohm s); (4) com mu tator w iring . The co mm utator has 4 series of 12 contact points,from which the current is carried off by wire brushes. These brushes ar e wired directlyto brushes at the back of experimental box making contact with th e rockin g grids.

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AUTOMATIC SHOCKING GRID 307

in the ceiling of one end of the box, and a lever projects from a wall at the oppositeend. In an earlier apparatus, the rats were observed to avoid the shockby climb-ing on the lever, hanging from crevices in the walls or ceiling, leaning betweenone grid and the wall, and sitting with hairless portions of the feet below thegrids. To complete the effect of the commutator and rotating bars, it wasnecessary to make all four walls electrodes by covering three walls with metalplates, insulated at the corners, and by putting a fine-mesh metal screen insidethe fourth one-way-vision wall. Since there were only twelve leads from thecommutator, but eighteen terminals to be wired, it was necessary to wire someof the grids and walls in parallel. Only those terminals which the rat would beunable to touch at the same time (e.g., the lever and opposite wall) were placedin parallel.

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200

3.0

100

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TIME-MINUTESFIG. 3. RECORDS OBTAINED BY CONDITIONING

Rats press a lever to eliminate shock, which recurred every 15seconds. Record A wastakenwith the present apparatus, and record B with a standard grid. Responsesare cumu-lative.This apparatus has been in use for more than 350 hours. At no time has a rat

been observed to escape punishment except by the desired response of pressingthe lever. Faeces are rocked off the grids immediately; and shock reception isinsured no matter what position the animal may assume in the box. The ap-paratus can thus be used unattended for long periods.

The records shown in figure 3 were obtained by conditioning rats to press thelever to eliminate shock. The shock recurred 15 seconds after each response, sothat at an advanced stage of conditioning (with no anticipatory responding),the curve should be a straight line with a slope of four responses per minuteFigure 3-A shows records taken with the present apparatus. A record takenwith a standard grid is shown for comparison at B. The dependability of thepresent apparatus is obvious.

REFERENCE1. SKINNER, B. F. Th e behavior of organisms: an experimental analysis.

Appleton-Century Co., 1938.New York: D.