Anim . Behav ., 15, 1967, 514-519

THE FORMATION OF ATTACHMENTS BY DOMESTIC CHICKS TO TWOTEXTURES

BY ANN TAYLOR, W. SLUCKIN, ROSEMARY HEWITT & P . GUITONDepartment of Psychology, University of Leicester

In a recent paper Sluckin et al. (1966) de-scribed some findings concerning the relativeattractiveness to 3-day-old chicks of surfacesdiffering in texture . In one experiment in whichchicks were reared singly in a pen with a smallopen-ended box which was either rough-linedor smooth-lined, it was found that the animalswere more likely to return to the box afterseparation when they had been reared with thesmooth-lined box than when reared with therough-lined one . In another experiment, chickswere reared in pens with two boxes, one smooth-lined and one rough-lined . It was found thatafter separation most showed a preference forthe smooth-lined box . It was quite clear thatchicks had tactile preferences, but it was notclear whether these preferences shifted as aresult of exposure to one or the other texture .

The present paper reports some further ex-periments mainly aimed at finding out whetherexposure to different textures makes chicksacquire different tactile preferences . In the twoexperiments just referred to, those chicks thatwere reared with one box were tested with thesame box and those that were reared with twoboxes were tested with both of them . In thethree experiments reported in this paper, chickswere reared with one box, either smooth-linedor rough-lined, but were subsequently testedwith both boxes. Different batches of chickswere exposed to the textures over differentperiods in order to see how fast preferences maybe established .

Experiment 1Method

Subjects were 120 domestic chicks, hatchedover a period of 10 weeks from Arbor Acre `50'eggs incubated in the laboratory . Each newlyhatched chick was allowed to dry off in theincubator before being moved into a grey card-board pen, 1 x 1 x 1 ft, open at the top endheated by a 60 W radiant-heat bulb . A chick inthe pen was isolated from other chicks, althoughit could hear them. Within each pen were waterand food dishes . Opposite these was a box,4# x 41 x 2 in ., fixed flat against the wall

514

2 in. above the floor. The ends of the box wereleft open so that a chick could get inside . Thefloor of each pen was covered with woodshavings.

All pens had grey walls and a box fixed ontoone of them . The boxes were essentially of twokinds, (a) lined inside with rough wool (hence-forth called R), and (b) unlined, the insidesurface being smooth (henceforth called S) .The lining used was a mohair and wool wovenfabric, which was commercially bleached andtherefore similar in colour to the white card-board interior of the unlined boxes . Sixty chickswere assigned to each type of pen, thirty forI day and thirty for 3 days (±2 hr) . The boxeswere of two different colours externally, eitheryellow or green : half of each batch of thirtychicks was assigned to each colour .

At the end of its stay in the `home' pen, eachchick was placed in a rectangular pen, 1 x 2 x 1ft, which contained two boxes, green for chicksraised with a green box and yellow for chicksraised with a yellow box . Of the two boxesplaced in any one pen, one was lined and theother unlined; both were fixed on the long sideof the pen, 2 in. from the floor of the pen and31 in. apart. For half of the subjects the boxsimilar to the `rearing box' was on the right,for the other half on the left .

Following pilot observations we found itnecessary to give each chick an initial 'settling-down' period, allowing it to recover from theeffects of being moved, explore its new environ-ment and discover the different textures of thetwo boxes . The animals were therefore left in apen for 15 min, and their behaviour was ob-served during the last 5 min only . A score wasassigned to the chick with respect to each boxin accordance with a seven-point behaviouralscale, ranging from 1 (no reaction to the box)to 7 (climbing right into the box) . The scale isgiven in full in Table I .

A chick was considered to have a preferenceif its score was higher for one box than for theother . The scoring system can be criticized onthe grounds that the ordinal position of re-sponses intermediate on the scale is equivocal

Table I. Behavioural Scale of Chick's Responses to a Box

Behaviour

Showed no reaction whatever to box

Crouched under box without making contact

Stood in light contact with box

Pecked at box

Stood beside box and rubbed against it

Stood at end of box with head inside it

Right inside the box

TAYLOR et al. : CHICKS' ATTACHMENT TO TWO TEXTURES

51 5

Score1

2

7

and inter-observer reliability undemonstrated .In fact, chicks virtually always showed the fullestresponse to a box or none at all ; that is, nearlyall scores were either 1 or 7, which are clearlybehaviourally distinct, and nearly all preferenceswere represented by a 1 to 7 difference betweenboxes .

ResultsSubjects were classified into those showing a

preference for S, those preferring R and thoseshowing no preference. The numbers of S- andR-reared chicks falling into each category areshown in Table II.Almost all S-reared chicks, whether tested

after a 24-hr exposure (first-day chicks) or aftera 3-day exposure (third-day chicks), preferredS to R. First-day R-reared chicks showed noclear preference for S or R although rathermore approached S . Most third-day R-rearedchicks, however, like S-reared chicks, showedpreference for the object with which they hadbeen reared . Thus, while preference for S was

Table II . Preferences of S- and R-reared Chicks for S- andR-lined Objects (Experiment 1)

The divergences between the distributions of S-rearedand R-reared chicks are statistically significant (Fishertest) ; for first-day chicks P<0 .05 and for third-day chicksP<0 .001 . The difference between first-day and third-dayR-reared chicks is not significant (X 2 = 3 . 31, 0 . 1 >P>0. 05) .

established after a 24-hr exposure, preferencefor R appeared only after a longer period ofexposure .An earlier experiment (Sluckin, Taylor &

Taylor, 1966) demonstrated that 3-day-oldchicks reared with both S and R showed prefer-ence for S when tested; a pilot study in thislaboratory suggested that the preference holdsalso among one-day-old chicks . This indicatesthat S might initially be more attractive than R .Thus, when an object was initially preferredattachment would very soon be apparent ;where it was not at first preferred, attachmentwould take longer to develop .To furnish support for this hypothesis more

varied exposure periods than those used inexperiment 1 are needed . It is also necessary toseparate the effects of different exposure timesupon preference from the effect (if any) of age attesting, by testing control chicks at differentages but without previous exposure to the testobjects. We should expect preference for the`rearing object' to remain high in the case of S-reared chicks at all ages, while preference in thecase of R-reared chicks would emerge graduallywith exposure, as distinct from age . Experiment2 was designed to provide data relevant to theseexpectations .

Experiment 2MethodIn all, 240 chicks were tested over several

weeks. For 120 of these the rearing and testinginvolved pens and boxes identical with those ofexperiment 1 . Sixty of these chicks remainedin the rearing pen for 2 days and sixty for 4days ; in each case thirty of the sixty were rearedwith S and thirty with R . Chicks were tested inthe same way as in experiment 1 .

The remaining 120 chicks were reared ascontrols : thirty spent 1 day, thirty 2 days,thirty 3 days and another thirty 4 days in a pen(1 x 1 x 1 ft) without a box . At the end of therearing period they were tested in a pen con-taining two boxes, and assigned scores in thesame manner as were the other chicks .

ResultsTable III gives the preferences of S-reared,

R-reared and control chicks of different ages .Expectations were only partly fulfilled by the

results. The number of control chicks preferringS was greater than the number preferring R,

Pref. S Pref. R No Pref.

S-reared 21 1 8First-day

R-reared 8 4 18

S-reared 18 0 12Third-day

R-reared 4 12 14

5 16 ANIMAL

Table III. Preferences of S-reared, R-reared and ControlChicks for S- and R-lined Objects (Experiment 2)

Significantly more first-day control chicks preferred Sto R: binomial test, P<0 .01 . The corresponding diverg-ence from chance for second-day control chicks : binomialtest, P=0 .09. No other departures from chance dis-tributions approach significance .the difference being most marked after 1 dayand negligible after 4 days .

R-reared birds preferred R and S in approx-imately equal numbers, after both 2 and 4 days.Their ratio of S/R preferences after two days was

BEHAVIOUR, 15, 4

within the range one could expect from the dataof experiment 1 ; but there was no trend to-wards a preference for R between 2 and 4 days .

The most discordant result was the relativelysmall preponderance of S-reared birds whichpreferred S . The proportions of chicks preferringS and R in S-reared and R-reared groups wereclearly not significantly different after either 2or 4 days . After 2 days there is, if anything,more suggestion of preference for S amongcontrol than among S-reared chicks . The dis-crepancies between these results and thoseexpected (on the basis of experiment 1) mighthave been due to sampling hazards . Anotherexperiment was therefore carried out to test thevalidity of the results of experiment 1 .

A further consideration in designing thisexperiment concerned the behaviour of chickswhich showed no preference. Theoretically, achick having no preference could have earnedany score between the extremes of 1 to 1 (noresponse) and 7 to 7 (entry of both boxes) ;in fact, however, scores in this class were all1 to 1 or 7 to 7 . Table IV, combining the relevantdata from experiments 1 and 2, shows thatrather more control chicks than experimentalchicks failed to manifest a preference . What is

Table IV. Frequencies of 7 to 7 and 1 to 1 Scores Obtained by Chicks in Experiments 1 and 2

*Data from experiment 1 ; data from experiment 2 without asterisk .Significant divergences, by chi-square test, between 7 to 7 and 1 to 1 distributions are indicated

in the table .

Pref. S Pref. R No Pref.First-day

controls 9 0 21

S-reared 8 6 16

Second-day{ R-reared 7 5 18

l controls 7 2 21

Third-day controls 6 2 22

S-reared 8 3 19

Fourth-day{ R-reared

(1 controls 6 4 20

3 2 25

7 to 7 1 to 1 TotalNo . pref.

(S-reared * 6 2 8

First-day

.jR-reared * 8 10 18 P<0 .05

L controls 5 16 21

S-reared 14 2 16

Second-day R-reared 14 4 18) P<0001

P<0 .001

controls 3 18 21 J

S-reared* 4 8 12

Third-day

R-reared* 11 3 14 P<0 .005

controls 4 18 22 J

S-reared 12 7 19 1

Fourth-day

R-reared 10 10 20P<0005

P<0 .001

IL controls 1 24 25 J

TAYLOR et al. : CHICKS' ATTACHMENT TO TWO TEXTURES

more striking, a significantly larger proportionof them failed to respond at all (scores of 1 to 1) .We wished to see whether this larger proportionof non-responding control chicks might be dueto their unfamiliarity with the test objects or,less specifically, to their relative lack of stimu-lation in the home pen .

For experiment 3 the same strain of chickwas not available, but in other respects it con-stituted, essentially, a replication of the experi-ment 1 conditions for testing chicks after 1 dayand the experiment 2 conditions for testing after2 days. Two control conditions were also used .One was identical to that in experiment 2 ;in the other, chicks were reared with an objectdissimilar from the test objects (S and R) butproviding visual and tactile stimulation .Method

Experiment 3The 240 subjects in this experiment were

domestic chicks hatched from Cobb eggs .Sixty chicks were assigned to each of four

groups: S-reared, R-reared, control A, control B .The rearing and testing procedures for S-reared,R-reared and control A chicks followed thoseof earlier experiments . Chicks in control B werereared in pens (1 x 1 x 1 ft) containing no boxbut an object of a different kind. This objectresembled a crown ; it consisted of a `collar'of stiff cardboard 5 in . in diameter and 11 in . inheight, to which were attached, at equal inter-

vals, four upright strips of cardboard each 44 in.high and I in. wide. Thus a chick could climb`inside' the object, which was the same colour(grey) as the walls of the pen .The testing procedure for control B was

identical with that for the other groups . Of thesixty subjects in each group, thirty were rearedin the pen for 1 day before testing and thirty for2 days. Scores were assigned as before .Results

The results of experiment 3 are seen in Table V .Consider first the three groups which replicate

parts of experiments 1 and 2 . For both first-and second-day chicks the number of chicks inS-reared and control A groups with a preferencefor S was considerably greater than the numberpreferring R. Both first- and second-day R-reared chicks, on the other hand, manifested apreference for S and R in approximately equalnumbers .

This tends to confirm our earlier conclusion,based on experiment 1, that an initial tendencyfor the birds to prefer S is modified by exposureto R for I or more days. The data leave roomfor doubt as to whether this initial preferencefor S can be strengthened by 1 or 2 days' ex-posure to that object, although this would seemto be a plausible assumption . It may be that theinitial preference is so marked as to leave littleroom for improvement, or that the method oftesting is not sufficiently sensitive to reveal suchstrengthening .

Table V . Preferences of Object-reared and Control Chicks for S- and R-linedObjects (Experiment 3)

Departures from chance distributions (x2 tests) :First-day chicks, S-reared, P<0 . 05 ;

Second-day chicks, S-reared, P<0 .005 ;First-day chicks, controls A, P<0 . 05 ;

Second-day chicks, controls A, P<0 . 05,

517

Pref. S Pref. R No Pref.7-7

1-1

S-reared 14 4 11 1

R-reared 5 5 18 2First-day

controls A 13 3 5 9

L controls B 8 4 4 14

(S-reared 13 1 12 4

R-reared 6 7 15 2Second-day

controls A 8 1 5 16

controls B 7 3 12 8

5 1 8

With regard to the incidence of responsive-ness, irrespective of preferences, no clear differ-ences separate the present from earlier data .The preferences of control group B chicks werenot very dissimilar from those of control groupA, though the preponderance of birds preferringS was less marked in B than A .

A comparison of the two control groups withregard to the incidence of responsiveness showsthat in second-day chicks the B group was moresimilar to S and R groups than was the A group ;more B than A chicks entered either one or bothboxes. This was not so for first-day chicks . There-fore if a non-specific effect results from object-exposure, it would seem to emerge later than thespecific one. However, the apparent differencebetween the control groups was small and thesuggestion of a non-specific effect cannot beregarded as confirmed without further experi-ment.

DiscussionLooking at the data of experiments 1, 2 and 3,

it is at once striking that a comparatively largenumber of chicks reared without any objectfailed altogether to respond to the boxes (scored1 to 1) . It is tempting to compare this finding withthe reported non-specific effects of early stimu-lation upon later behaviour (e.g . Denenberg,1962). However, our behavioural scale wasdesigned to measure responsiveness to specificobjects, rather than general activity, and thuscould not wholly support the analogy . More-over, both control groups A and B were similarin that both produced a higher incidence of 1 to Iresponses than did either S- or R-reared groups .This suggests that the higher rate of entry foundamongst S- and R-reared groups was due not somuch to a non-specific effect of greater environ-mental complexity as to specific experience of abox. This, we may suppose, established thehabit of entering the box, which in some caseswas generalized to both boxes .

Returning to the central issue, the results ofexperiment 3 tend to confirm the conclusionsdrawn from experiment 1, leaving experiment 2as the `odd man out' .

As far as a valid comparison is permissibleamong the experiments, it would appear that theonly obvious discrepancy lies in the unexpectedlylow proportion in experiment 2 of S-rearedchicks preferring S. We can therefore maintainthe conclusion that exposure to R for one day ormore can modify an initial marked tendency toprefer S, as operationally defined here, and estab-

ANIMAL BEHAVIOUR, 15, 4

lish a new preference for R, although it is notclear that initial preference for S can be strength-ened by exposure .

Since no comparison of the data for the fourth-day chicks in experiment 2 can be made withdata from either of the other two experiments,it is not possible to say whether the trend wouldcontinue beyond the third-day tests (when thebirds are between 3 and 4 days old). It is possiblethat the data of experiment 2 for the fourth-daychicks reflect a change in their behaviour notdictated by experience .

We suggested on the basis of experiment 1that a preference for box R would be increasinglymanifested with lengthening exposure . This hasnot however been conclusively demonstrated,not only because the fourth-day chicks failed toconfirm this, but also because in experiment 3 thepreferences of first- and second-day R-rearedchicks were not markedly different. It is possiblethat the maximum modification occurs aftersome 24 hours' exposure, although this is notborne out by results obtained with the R-rearedbirds in experiment 1 ; a replication of the workis needed, using larger numbers, to clarify thisquestion . It would be interesting to adopt theprocedure of repeated testing of the same chickafter 1, 2, 3, 4 and more days' exposure in orderto observe shifts of preference .

What significance have these findings, par-ticularly in relation to the phenomenon of im-printing? Imprinting has, of course, manydifferent connotations, but we are thinkingparticularly in terms of the formation of socialattachments in the newborn chick . Visualpreferences expressed in the young chick'sapproach or following response to a movingobject can be determined or modified by earlyexperience. This is attested by the results ofnumerous experiments (Sluckin, 1964 ; Bateson,1966). For instance, in a recent experiment(Taylor & Sluckin, 1964), newly hatched chickswere reared singly with a moving box or in pairsand tested a day later for choice between themoving box and a live chick. Without excep-tion, the chicks showed a strong preference forthe familiar figure . The attachment was formedwhether or not food and water were present inthe rearing pens, and was therefore independentof these conventional sources of reinforcement .It is tempting to see evidence in our presentexperiment, and by analogy with studies ofvisual imprinting, that chicks may become im-printed to objects of specific textures .

TAYLOR et al. : CHICKS' ATTACHMENT TO TWO TEXTURES

519

Several questions follow naturally from such acomparison . How lasting are the modifications ;would a chick, for instance, retain an acquiredpreference for a rough-lined box if a smoothbox were then made constantly available? Doestactile stimulation contribute to the establish-ment of a visually guided following-response orattachment, as it seemingly does in somemonkeys (Harlow, 1958 ; Harlow & Zimmer-mann, 1959)?

SummaryIn three experiments chicks were reared with

either a smooth-lined or a rough-lined box justbig enough to be entered, and were then testedfor preference in a pen containing both boxes .It was found in experiment 1 that conditions ofrearing influenced the chicks' preferences in thedirection of the `rearing' texture, the effective-ness of rearing apparently depending to someextent upon the initial attractiveness of thetexture used . The results of experiment 2 weredifficult to interpret, but those of experiment 3tended to confirm the finding, as well as indicat-

ing that controls reared without an object orwith one unlike the smooth-lined and rough-lined boxes were less responsive in the choicetest. By analogy with visual imprinting, it wouldappear that chicks may be capable of becomingimprinted to objects of specific textures .

REFERENCESBateson, P . P. G. (1966). The characteristics and con-

text of imprinting . Biol. Rev ., 41, 177-220 .Denenberg, V . N . (1962) . The effects of early experience.

In The Behaviour of Domestic Animals (ed. byE. S . E . Hafez). London : Bailliere, Tindall & Cox .

Harlow, H . F . (1958). The nature of love . Am. Psycho-logist, 13, 673-685 .

Harlow, H . F . & Zimmermann, R. R. (1959) . Affectionalresponses in the infant monkey . Science, 130,421-432 .

Sluckin, W. (1964) . Imprinting and Early Learning .London: Methuen.

Sluckin, W., Taylor, K. F. & Taylor, Ann (1966) .Approach of domestic chicks to stationary objectsof different texture. Percept. mot . Skills, 22, 699-702 .

Taylor, K . F . & Sluckin, W . (1964). Flocking of domesticchicks . Nature, 201, 108-109 .

(Received 22 November 1966 ; revised 21 March 1967 ;Ms. number : 709)