Climbing suppression: Passive avoidancein the turtle1

IRWIN M. SPIGEL2 AND KENNETH ELLIST EMPL E UNIVERSIT Y

TABLE IMean Number of Seconds per Trial for each Shock Group in

Five E xtinc ti on Trials

Group Trial

2 3 4 5

O- volt 200.2 155.8 296.2 436.0 460.0

3D-volt 161..5 279.8 310.6 550.5 288.545-volt 360.0 481.1 363.3 414.0 495.660-volt 458.7 724.8 380.0 651.7 326.790-volt 404.8 321.3 305.1 340.7 348.0

was attained. Five daily 1/2-hr. shock-free extinctiontrials follwed.

ResultsFunctions relating both number of trials to criterion

and mean second's of climbing per trial to criterion,to shock level are shown in Fig. 2. One S in the 0 volt(control) group failed to zero out and trials werearbitrarily halted after the 50th day. Analysis of varianceacross shock intensities are highly significant in thecase of both acquisition measures (F=6.9, p< .01;F=19.2. p< .01, respectively; df=4). Although the dif­ference between the O-volt and 30-volt groups is notstatistically significant in number of trials to criterion,the difference between these groups with respect tomean second's per trial to criterion is highly significant.

With regard to the five extinction trials, neither totalclimbing time nor mean second's of climbing statisti­cally differentiated the groups. The latter values aregiven in Table 1.

DiseussionPassive avoidance, in the form of a suppression of

the turtle's natural response to climb from a walledenclosure, was obtained without difficulty, and shownto vary with shock intensity in a negatively acceleratedmanner. The persistence of this response is reflectedin the high mean second's per trial for Ss in the O-volt

MERCURYSWITCH(.n~)

115VAC

CLOCK

115vRELAY

reiCAGE

FlOOR ~ARIACCAGEWAll

115 VAC

Fig. 1.

AbstraetThe persi stent effor t by the turtle Cnrys cmys to

cli mb from a walled enclosure is utilized in a situationwhich allows for the study of passive avoidance inthi s sp eci es. A parametric examina tion of the effectsof shock intens ity on this behavior produced the expectedgr adie nts for two measures of avoidan ce ac quis iti on ,but failed to yie ld differences in extinction.

ProblemThe ave rsive nature of walled confinement to turtles

of the species ClitYSf III YS pi c (a ha s been previouslyr eported by the author in connect ion with studies ofdetou r lea rning (Spi ge l , 1964) . When confined in suchfashion. Ss a re apt to spend much of their time a t­te mpti ng to climb out of the enclosure. The currentexper iment was designed to explore the possibility ofutili zing th is natural climbing response in the examina­tion of pa ss ive avoidance in Chrysc mys. Specifically,the suppress ion of th is r esponse as a function of shockinte ns ity was investigat ed with appa ratus in which theS's nat ur al r esponse produced the noxious cont ingency .

Subj.·.·.sTwenty mal e and 10 female Chrys etnys were em­

ploye d . Ss wer e divided se mi- r andomly into five groups,the rcs tr icti on being the a ssignment of two females toeac h. Ss we re be tween 3 and 4 yr. of age as estimatedfr om ca ra pace length .

\pparutusA ci r cu lar metabolism ca ge , 8-1 /2 in high and 8 in in

diameter was wired into the c ircuit shown in Fig. 1. Amercu r y switc h was taped to the forward decline of theS's ca rapace such that when a lie of approximately 200

was attained , a shock circuit was completed by Sbet ween the floor and wire wall of the cage which hadbeen insul at ed from one another. Closing the switcha lso s imult aneous ly ac ti va ted a clock. Both circuits werebroken by a r eturn of the S to the horizontal. In thismann e r. Ss r eceiv ed shock only while climbing, and ar eco rd of total climbing time (and seconds of shock) wasobtained. Shoc k level was controlled by a variabletran sformer. A square sc r een , 14 in ona side and 12 inhigh sur r ounded the climbing cage. Flexible wire wasused for the mercury switch connec tion and drawn up­ward through the wire cover of the cage with sufficientslac k to allow complete freedom of movement for the S.Proeeduri'

Fiv e shock inte ns iti es were employed: 0,30,45,60 ,and 90 volts AC, one group of Ss exposed to each. Sswere given 1/2 hr. sessions daily in the apparatus untila c r ite r ion of one full se ssion totally free of climbing

Psych on Sci. 1965. Vol 3 215

z 35 ---- TRIALS TO CRITERION 1050co

OF CLIMBING;c 0-- - -0 SEC:S;: 30 850 ~... ..'" ze 25 650 ...... ...

!'"~ 20 , 450 ...;,... ,, ~... 15 \ 250 &... ,

\...

"" \ ;;z

10 \ 50 ...z 'b...c '"... ":. " 25

''''0--------

30 45 60 90

SHOCK INTENSITY (volts)

F i g. 2. Functions relating two measures of passive avoid anceacqui si tion to shock intensi ty .

group, which is in essence an habituation contro l. OneS in this group never did reach zero and could notcontribute to the extinction data.

Though two measures of acquisition were found tobe sensitive to differential shock level, the five-trialextinction procedure failed to produce differences in

216

mean second's of cli mbing. It is pos sible that an extendedseries of exti nction trial s may yie ld differences rel atingto performance during ac quisition.

The need for fur ther study of both extinction per­formance and the use of shock as an aver s ive stimulusfor the turtle is also sugges ted by the fact that O-voltand 30-volt Ss differed with r espect to amount ofclimbing, a s expe cted, but not in number of trial s tocriterion. This findin g may be analogous to the obs erva­tion in operant s ituati ons of reduction in response ratebut not in tot al number of responses when a mildlypunitive s ti mulus is introduced (Skinner , 1938).

In any case, the procedure de scribed appears en­tirely feasible for further study of passive avoidancein a reptile species, and especially us eful for psycho­pharmacological investigation.

ReferencesSpige l , I. M. Detour l earni ng, ret enti on and di srupt i on in the fresh

water turtle . J . compo physio/. Psuch ol ., 1964 , 57 , 108-11 2.Skinn er , B . F . The behavior of organi sms: an experim ental anal-

ysis. New York : Appleton-Century-Crofts , 1938 .NoteI. T hi s resea rc h was supported by Grant No. MH-08679 from t he

USPHS.2. Now at the Uni versi t y of T oronto

Psychon . sct ., 1965, Vol. 3