Respuesta a Diferentes Grados de Novedad

RESPONSE TO DIFFERENT DEGREES OF NOVELTY:THE INCIDENCE OF VARIOUS ACTIVITIES'

DALBIR BINDRA and NAHUM SPINNER

MCGILL UNIVERSITY

When a rat is exposed to a novel situation, it engages in a variety of activities. It"freezes," walks around, sniffs at things, approaches toward or withdraws fromthings, grooms itself, lies down, and so on. These activities also occur in familiarsituations; however, the relative frequencies of their occurrence seem to be differentin unfamiliar situations. Recent studies of rat behavior in novel situations havegiven two of these activities special attention. One of them is locomotion throughthe new situation, or approaching the unfamiliar elements in a familiar situation,and has been labelled "exploratory" behavior (Berlyne, 1955; Montgomery, 1953);the other is withdrawal from or avoidance of certain parts of the situation, and hasbeen referred to as "fear" behavior (Montgomery, 1955; Montgomery & Monk-man, 1955). In these studies, little or no attention has been paid to the other ac-tivities (e.g., grooming, sniffing, freezing) which the rat is also likely to perform ina novel situation. The present investigation is concerned with a more detailed ana-lysis of the behavior of the rat in such situations. It is prompted by the assumptionthat the various specific questions posed by exploratory and fear behaviors are spec-ial cases of one general problem: In what way do the responses of animals changewhen they are exposed to situations of varying degrees of novelty? This formulationis here proposed as an alternative to the traditional view which links each differenttype of reaction to novelty with a specific "explanatory" construct such as "ex-ploratory drive" or "fear drive." (See DISCUSSION.)The general plan of this investigation involved observing rats in three situations

varying in degree of novelty, and recording their behavior in terms of the followingexhaustive categories of response: sniffing (S), locomotion (W), grooming (G),"freezing" or sitting motionless (F), lying or sitting (L), and miscellaneous (M).Degree of novelty was defined independently of the animals' response. Rats lived incages.that possessed certain visual, tactual, and auditory characteristics, and wereobserved (tested) under conditions where these characteristics had been altered.Each test condition provided a different amount of stimulus change from the livingcages; the amount of such stimulus change defined the degree of novelty.

METHODSubjects

Thirty male hooded rats, about lQO days old, served as subjects in this experi-ment. They were obtained from the rodent colony maintained by the Royal VictoriaHospital in Montreal and, on arrival at the psychology laboratory, were immedi-ately transferred to specially prepared living cages.

Living and Testing ConditionsEach living cage consisted of a wooden floor and 1/4-inch wire-mesh walls and

roof; it was 12 by 12 by 12 inches. Three of the walls were covered with black card-'In a slightly modified form, this paper was read at American Psychological Association, Washing-

ton, 1958. The research reported here was supported by a grant (A.P. 27) from the NationalResearch Council of Canada.

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board on the outer surface; the fourth wall and the roof were uncovered. Sawdustwas spread over the floor of the cage, and the sawdust was changed abdut twice aweek. Six rats lived in each of five such cages.The three testing conditions provided varying amounts of stimulus change from

the living cages. Condition N-I provided the least change. In this case the test cageresembled the living cages in all respects except one: instead of being covered withplain black cardboard, the three walls were covered with cardboard having alter-nate white and black stripes of equal, 1 inch, width. Condition N-2 provided asomewhat greater degree of novelty: in addition to having striped walls, the floorof the test cage was covered with a sheet of fine (about 1/16-inch) aluminum wiremesh. Condition N-3 provided the greatest amount of stimulus change: the testingcage itself was similar to the N-2 cage in structure, but a "white" noise (about 73decibels), produced by the escape of compressed air from a jet, was introduced intoit.

ProcedureThe rats were given 10 days to become habituated to their living cages. Following

this period, six rats were tested per day, two under each of the conditions N-i, N-2,and N-3. Each rat was tested under only one condition. The rat was removed fromits living cage, carried to the testing room, and placed in the appropriate test cage.The experimenter sat directly in front of the uncovered wall of the cage; a lamp ofmedium brightness2, directed toward the cage, was placed between the cage and theexperimenter, about 15 inches from the center of the cage, in order to prevent theanimal from seeing him. The behavior of the rat was observed and recorded for 15minutes. The rats had free access to food and water at all times except during theperiod of testing.Response CategoriesA modified time-sample method, described by Bindra and Blond (1958), was used

for recording the various aspects of the behavior of rats. Essentially, it consists ofrecording the particular act in which the animal is engaged at the beginning of eachx-second interval. In the present experiment the response at the beginning of each6-second interval, indicated by the periodic flash of a small lamp operated througha timer, was recorded. Thus, a total of 150 entries (F, S, S, G, S, F, etc.) for the15-minute observation period was made for each rat. Each entry consisted of one ofthe following categories of response:

F freezing: rat sits rigidly motionless, or slightly trembling, in ahunched or prone position, with eyes open; sometimes accompaniedby chattering of teeth.

S sniffing: rapid movement of whiskers, nose twitching, sound of sniff-ing; usually accompanied by neck-stretching, rearing, or walking.

W locomotion: rat walks or shifts its position in such a way as to in-volve all four limbs.

G grooming: rat licks, scratches, or "cleans" any part of its body.

2Unfortunately, the exact intensity of the light is not known. It is our impression that a bulb ofnot less than 60 watts and not more than 100 watts was used.

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RESPONSE TO DEGREES OF NOVELTY

L lying or sitting: rat sits relaxed and motionless, or sleeps; abdomenrests on the floor of the cage.

M miscellaneous: a left-over category for responses such as chattering ofteeth (without freezing), licking parts of the apparatus, rearing (with-out sniffing), gnawing on bits of food and sawdust, and so on.

The miscellaneous category was introduced to make the categories jointly ex-

haustive. As the categories are not entirely mutually exclusive, a precedence hier-archy was introduced for cases in which two different responses occurred concur-

rently. The order of precedence was that in which the categories are listed above..(In fact, only sniffing and walking tended to occur together; this resulted in an

entry of "sniffing.") The reliability of this method and the interjudge concordance(85 per cent) in classifying responses are well within the generally acceptable range

(Bindra & Blond, 1958).

RESULTS

The mean numbers of F, S, W, G, and M responses made by the three groups often rats in the 15-minute testing period are presented in Table 1. Except for F, the

Thble 1

Pr%Eqmlee of Oeomrroe of the Variou Responses

Under Tbree Degree of Novelty euring the 15-sit. Teting feriod.

(3ach group osisted of 10 rate.)

Respone Degree of Novelty

N-1 N-2 i-3

mesa 11.9 19.2 16.4P-- freesing Median 5.0 11.0 19.0

SD 17.9 18. 12.6

mean 95.4 76.5 *3.300S sniffing median 100.0 76.0 60.5

SD 13.3 18.1 12.5

mean 9.0 8.7 11.2W -- locomotion median 9.0 8.0 10.0

SD 5.0 4.7 3.3

mean 25.7 42.6 55.2**o -- grooming median 24.5 29.5 ".5

SD 9.7 22.8 14.2

Mean 7.7 3.0 3.7M -- iscellanous Median 6.5 2.0 4.0

SD 4.5 2.5 2.4

**Difference between this figure and the correspondlng figure under N-1 tisignilicant at beyond the .01 level (Median teat, two-tailed).

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median values fell close to the corresponding means. Since only 3 of the 4500 re-sponses recorded fell into the L category, L is not included in the table. It isevident that S and G had a much greater frequency of occurrence than the other re-sponses. In spite of large variability, the S and G scores in the situation N-1 weresignificantly different from those in N-3; the corresponding scores in N-2 were in-termediate between those in N-1 and N-3 but were not significantly different fromthem. Thus, the animals engaged in more S in N-1 than in N-2, and more in N-2than in N-3; but G showed changes in the reverse order. This means that withinthe present conditions, the greater the novelty, as defined here, the less the ratsniffs and the more it grooms.For a more detailed analysis of the data, the means of the mean frequencies of

occurrence per minute of the various responses during each of the five successive3-minute periods of observation were determined. These are shown in Fig. 1 to 4.Figure 1 shows that the frequency of S responses is quite high and about the samefor the three groups during the first 3-minute period of the total testing time; butthese scores decrease at different rates, resulting in somewhat greater differencesduring the last 3-minute period. Similarly, starting with similar G scores, thedifferences between the three groups increase progressively during the successive3-minute periods (Fig. 2). Figure 3 shows a progressive increase in F. However,an increase in F was not observed in all animals; only some of the rats in each groupare responsible for the observed increase. The increase in F probably "accountsfor" the decline in G during the last, fifth, 3-minute period, seen in Fig. 2; this

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SUCCESSIVE 3-Mt PERIbDSFigure 1. The frequency of occurrence per minute of S (sniffing) responses under three conditions

presenting different degrees of novelty. The p values written near certain points on the curves representthe level of significance of the difference between those points and the corresponding points for the first3-minute period.

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RESPONSE TO DEGREES OF NOVELTY 345

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Figure 2. The frequency of occurrence per minute ofG (grooming) responses under three conditionspresenting different degrees of novelty. The p values written near certain points on the curves representthe level of significance of the difference between those points and the corresponding points for the first3-minute period.

conjecture is supported, for example, by the record of Rat No. 24 (Fig. 6). Figure 4presents the course of W responses through the 15-minute test; a progressive de-cline is seen for all groups. Differences between the means for the first 3-minuteperiods and those for the fourth or fifth 3-minute periods are significant for all ac-

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Figure 3. The frequency of occurrence per minute of F (freezing) responses under three conditionspresenting different degrees of novelty. The p values written near certain points on the curves representthe level of significance of the difference between those points and the corresponding points for the first3-minute period.


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Figure 4. The frequency of occurrence per minute of W (locomotion) responses under three condi-tions presenting different degrees of novelty. The p values written near certain points on the curves rep-resent the level of significance of the difference between those points and the corresponding points forthe first 3-minute period.

tivities for conditions N-2 and N-3, and for G and W for condition N-1. The levelsof significance of these differences are shown in Fig. 1 to 4. These results suggestthat progressive changes in the incidence of various activities are somewhat morelikely to occur under conditions of greater stimulus change. The initial responseto novelty seems to be an increase in S in all cases, but the progressive changes varywith the degree and duration of the stimulus change. The M scores were too few tobe plotted in this way.

Except for F, an examination of the records of individual animals reveals no re-markable individual differences. In S, for example, 29 of the 30 animals showed adecline from the first 6 minutes to the last 6 minutes of the test session; the ex-ception was an animal in N-1 whose S scores showed an increase of only one. Sim-ilarly, all the animals showed an increase in G from the first to the last 6 minutesof the test session. There was also no exception to the decrease in W from the firstto the last 6 minutes, though the average curve (Fig. 4) shows a slight increase forthe last 3-minute period in the N-3 condition. Even with F, the animals are con-sistent with each other in that those which freeze at all do so more in the later thanin the earlier part of the test session. However, marked individual differences ap-pear in the frequency of F responses and in the pattern of their occurrence over thetest session. Four different types of records, all obtained in N-3, are shown in Fig.5; individual records obtained in the other two conditions were similar to thoseshown here. These four patterns were about equally frequent in each of the threeconditions.

Figures 6 and 7 show the exact way in which S, G, F, and W responses covaryin individual animals. Records of two animals are presented, one a "freezer" andthe other a "non-freezer." These graphs represent, quite faithfully, the behaviorof freezers and non-freezers in all the conditions.

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Figure 5. Four different types of individual records showing the changes in the frequency of F re-

sponses during the five successive 3-minute periods. All the four records were obtained in conditionN-3, but are quite representative of the other conditions too.

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Figure 6. The typical way in which S, G, F, and W responses covary in "freezers" (Rat No. 24).

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The total number of shifts from one activity to another (i.e., the number of timesany two successive entries were not the same) was also determined for each animaland averaged for each group. No significant differences between the groups, or pro-gressive changes within any group, were found. Thus, as judged by the presentmethod of sampling activity, the different degrees of novelty did not produce anydifferences in stereotypy or randomness of behavior.

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Figure 7. The typical way in which S, G, F, and W responses covary in "non-freezers" (Rat No. 29).

Casual observation indicated that although the animals did not seem to react tothe light in any specific way, they did sniff at the striped walls in a manner sug-gesting a specific response to that visual pattern. However, in this study, no sys-tematic attempt was made to separate the responses of the animals to novelty orstimulus change per se and their responses to certain particular elements in thetest situation.

DISCUSSION

The current approach (Berlyne, 1955; Montgomery, 1955; Dember & Earl, 1957)of interpreting the reactions of animals to novel stimuli in terms of exploratoryand fear "drives" is quite inadequate to deal with the results of this study. Typi-cally, the drive approach assumes a priori that a certain type of activity representsa particular drive; and the drive, in turn, is assumed to be evoked by the novelty as-pect of a stimulus situation. Possible statements based on either one of these as-sumptions can be shown to be inadequate in view of the present results. Forexample, if S in the present case is assumed to represent "exploratory drive"evoked by novel stimulation (Montgomery, 1953; Berlyne, 1955), it is not clear why

6

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I


increasing novelty leads to a decrease in the frequency of occurrence of S. Similarly,ifG is considered a manifestation of "fear drive" (though there is no clear basis ofdoing so), and if this drive is assumed to decrease with increasing familiarity witha situation (Montgomery, 1955; Montgomery & Monkman, 1955), why does thefrequency of occurrence of G increase (Fig. 2) through a major part of the testingperiod? Also, the drive constructs, in their present form, do not provide any wayof dealing with the F and M responses that also occur in a novel situation.We do not have any specific interpretation of the obtained results to offer. Little

is gained by developing, post hoc, an ad hoc interpretation of experimental findings.Rather than postulate new drives or modify the properties of the "existing"ones,we are inclined to formulate the problem of behavior in novel situations withoutreference to drive theory. We consider the F, S, W, G, L, and M responses, as wellas many other types of activities, to be already developed in the animal's repertoirebefore it is introduced into the test situation. These responses occur under a varietyof circumstances and are not peculiar to novel situations. Thus, the basic questionbecomes that of the factors or sets of variables that determine the differential fre-quency of occurrence of these responses under varying degrees and durations ofnovel stimulation. Within the general framework suggested elsewhere (Bindra,1959), three sets of variables seem to be important in this connection: (a) the sen-sory cues that constitute the novel situation; (b) the extent to which the level ofarousal or excitement of the animal is raised in the novel situation; and (c) the habitstrengths of the various classes of responses in the animal's repertoire. The exactroles of these factors in determining the relative frequencies of occurrence of dif-ferent classes of activities during continued exposure to various types of novel situ-ations remain to be determined. This formulation cannot, of course, be regarded asan explanation of behavior under conditions of novelty. Rather, it points to thetype of variables whose systematic manipulation is likely to result in a satisfactoryexplanation.

SUMMARY

In what way do the responses of animals change when they are exposed to situ-ations of varying degrees of novelty? The present experiment was a study of noveltyin the rat, with novelty defined in terms that are independent of the animal's re-sponse.

Thirty rats lived in cages that possessed certain visual, tactual, and auditorycharacteristics. In three other (test) cages, these characteristics were altered insuch a way that each test cage provided -a different amount of stimulus change fromthe living cages. Cage N-I provided the least change or novelty, cage N-3 providedthe greatest, and cage N-2 was intermediate in novelty. Ten animals were observedindividually for 15 minutes in N-1, and 10 each were similarly observed in the othertest cages. A modified time-sample method was used to record various aspects ofbehavior in terms of the following exhaustive categories of response: sniffing, walk-ing, grooming, freezing, sitting, and miscellaneous.For the testing period as a whole, the following statistically significant results

were found. Scores for sniffing were the highest for N-1, and the lowest for N-3;grooming was highest in N-3, and lowest in N-1. Also, progressive increases or

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decreases throughout the 15-minute testing period were observed for all the activ-ities with conditions N-2 and N-3, and for some of the activities with N-1. No dif-ferences between the conditions in stereotypy or randomness of behavior werefound.The observed relations between the novelty of test situations and the incidence of

various classes of response cannot be adequately interpreted in terms of the tra-ditional constructs of "exploratory drive" and "fear drive." An alternative formu-lation of the problem, pointing to new lines of experimental work, is offered.

REFERENCES

Berlyne, D. E. The arousal and satiation of perceptual curiosity in the rat. J. comp. physiol. Psychol.,1955, 48, 238-246.

Bindra, D. Motivation, a systematic reinterpretation. New York: Ronald, 1959.Bindra, D., and Blond, Joyce. A time-sample method for measuring general activity and its com-

ponents. Canad. J. Psychol., 1958, 12, 74-76.Dember, W. N., and Earl, R. W. Analysis of exploratory, manipulatory, and curiosity behaviors.

Psychol. Rev., 1957, 64, 91-96.Montgomery, K. C. Exploratory behavior as a function of "similarity" of stimulus situations. J. comp.

physiol. Psychol., 1953, 46, 129-133.Montgomery, K. C. The relation between fear induced by novel stimulation and exploratory behavior.

J. comp. physiol. Psychol., 1955, 48, 254-260.Montgomery, K. C., and Monkman, J. A. The relation between fear and exploratory behavior. J.

comp. physiol. Psychol., 1955, 48, 132-136.

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