Anim. Behav ., 1969, 17, 3-8

CHANGING COLOUR PREFERENCES OF CHICKS

BY ANN TAYLOR, W. SLUCKIN & ROSEMARY HEWITTDepartment of Psychology,

Experiment 1Methods

The subjects were 242 chicks hatched from`cobb' eggs in the laboratory ; 68 were assignedto the exposure group, 70 to the imprintinggroup, 64 to the conditioning and 40 to a controlgroup. Each chick was moved from the in-cubator into a grey cardboard pen, 1 ft x 1 ft x1 ft (30 cm 3), open at the top and heated by a60 W radiant-heat bulb. A chick in the pen wasvisually isolated from other chicks, although itcould hear them. Food and water were pro-vided in each cage .

After 24 hr each chick was removed from itspen and placed in a runway 22 in . (56 cm) long,6 in . (15 cm) wide and 8 in. (20 cm) high. Thefloor was marked off in 1-in . (2 . 5 cm) strips ;the central line was labelled 0 and the lines toeither side of it were numbered 1 to 11, line 1Icoinciding with the end of the runway . Clippedto each end of the runway was a 6 in . (15 cm)square of coloured plastic ; one end was blue(Oroglass, Blue 2326, „ in. (3 mm) thick . and theother red (ICI Perspex Sheet 461). All thecoloured plastic used in these experimentswas rubbed down with sand paper to minimizereflection . A light bulb was suspended directlyabove each end of the runway .

A chick was placed in the runway on the zeroline and facing a long side ; a stopwatch wasstarted and the chick was observed on everyminute for 5 min, and its position noted . If thechick was between lines 6 and 11 towards thered end of the runway, it was given a score of-{-1 ; if it was between lines 6 and I 1 towardsthe blue end, a score of -1 ; otherwise it re-ceived a score of 0. Thus the total scores duringthe 5-min test ranged from +5 to -5 . A positivescore was taken to indicate a perference forred, and a negative score a preference for blue .

After this test the chick was removed fromthe runway for 2 hr, during which time itreceived the experimental or control treatmentto which it had been assigned . At the end of 2 hrit was replaced in the runway and tested, andits behaviour scored, as before. For half thechicks in each group red was on the right of theentry point and blue on the left ; for the rest thepositions were reversed . The colours for any

Young nidifugous birds readily show prefer-ences for some colours over others . Thorndike(1911) observed domestic chicks pecking colouredspots, and Lashley (1916) studied the chick'sapproach responses to coloured surfaces . Morerecently, chicks' preferences for colours wereinvestigated by Schaefer & Hess (1959), bySmith & Hoyes (1961), and by Smith & Meyer(1965). Kear (1964) tested pecking preferencesfor colours in the young of many species ofAnatidae and Phasianidae, and Weidmann(1965) similarly reported on young moorhensand coots . Findings of all these workers havebeen dependent not only on the methods oftesting but also on the characteristics of thevarious colours used and especially on theirluminosity (Kear, 1966) .

Very few attempts have been made to studychanges in preference rather than colour prefer-ences as such. Gray (1961) attempted to studycolour preferences of domestic fowl chicks as afunction of maturation ; he reported that choices,as measured by approach responses, tended tochange with age . Our own interest has been inthe stability or otherwise of colour preferencesin relation to various types of intervening ex-perience . In our experiments we used as subjectsdomestic fowl and Japanese quail chicks . Wetested them individually for approach prefer-ence between two given colours, and then testedeach bird again in the same way after `training'of some kind with one or the other colour orafter no training.

Four experiments are reported . Experiment Iis concerned with the efficacy of differentmethods of altering the domestic chicks' colourpreferences. As `training' methods we used(a) exposure to coloured walls of rearing pens,(b) conventional imprinting and (c) a form ofconditioning with heat as the unconditionedstimulus (UCS). Experiment 2 is concerned withthe variable of duration of experience, usingonly one method of effecting a shift of prefer-ence, namely the `exposure' procedure. Experi-ments 3 and 4 attempt to shed some light onthe generality of the effects we have found . Tothis end we used a new pair of colours, and alsoexperimented with a further species, the Japanesequail .

University of Leicester

4

ANIMAL BEHAVIOUR, 17, 1

one chick were in the same position in both thepre-training and the post-training tests . Experi-mental procedures were as follows :

(a) Exposure. After test 1 the chick was placedin a pen, 1 ft x 1 ft x 1 ft (30 cm 3), three sidesof which were lined either with red or with bluePerspex. Water was available in the pen . Halfthe chicks were exposed to red in this way andhalf were exposed to blue .

(b) Imprinting . The chick was placed, aftertest 1, in a grey circular pen 18 in . (46 cm) indiameter and 12 in. (30 cm) high in which waterwas available. In the centre of the pen was a smallsynchronous motor driving a cam which switchedon another synchronous motor for 21 sec andoff for 31 sec. This motor caused a 2-in . (5 cm)square of Perspex (red or blue) to move roundthe pen at a height of I in . (2 .5 cm) from theground. The chick was given 2 hr inside the penwith the moving object . As expected, somechicks followed the Perspex square .

(c) Conditioning. The conditioning apparatusconsisted of one tank 18 in . x 18 in . x 81 in .(46 cm x 46 cm x 21 .5 cm) inside another tank20 in . x 20 in . x 81 in . (51 cm x 51 cm x 21 . 5cm) through which there was a continuous flowof cold water. The inner tank was incompletelydivided by four partitions each 61 in . (16 . 5 cm)long. Two of the compartments thus formed werelined with red and the other two with blue ;the compartments diagonally opposite were ofthe same colour. Heating lamps were supportedabove opposite compartments so that eitherthe two red or the two blue ones were heated inthe course of each 2-hr experiment . One lampwas switched on for 7 min . When it switched off,the lamp opposite switched on for 7 min .Successive heating of the two like-colouredcompartments continued in this way throughoutthe 2-hr training period . The compartmentsnot heated by lamps were kept cold by the sur-rounding water. A chick was placed at the centreof the inner tank, with access to all four com-partments . Chicks tended to move to the heatedcompartment, from red to red, or from blueto blue, though some stood shivering in the redcompartments when the blue ones were beingheated .

Control GroupEach control chick was placed after test I

in a grey cardboard pen similar to that in whichchicks were initially reared, and remained inthis pen until retested after 2 hr.Chicks in the experimental groups were

assigned alternately to red-training and blue-training, not on the basis of their initial score .Results

It will be seen from Table I that a clear prefer-ence emerged on test 1 for red over blue, chicksin all groups showing essentially the samepattern. In no case were the proportions of red-preferring, blue-preferring and non-preferringbirds different for red-training and blue-traininggroups .

Table I. Initial Preferences of Birds in Experiment 1

***Divergence from chance distribution : P<0.001(X 2 test)

A `shift of preference' score was obtained bysubtracting the score on test 1 from the score ontest 2 . If the resulting score was negative it wastaken as showing a shift of preference towardsblue ; if positive, as showing a shift of preferencetowards red. Thus a shift towards red, forexample, might be represented by a change frominitial preference for blue to preference for red ;from a strong initial preference for blue to aweaker preference for blue ; from initial prefer-ence for blue to no preference ; from no initialpreference to a preference for red ; or from aweak initial preference for red to a strongerpreference for red . The direction and statisticalsignificance of shifts of preference were ex-amined by means of the Wilcoxon signed-rankstest .

Table II shows the changes in preferencefrom test 1 to test 2 for birds in all three experi-mental groups and for the control birds . Inall three experimental groups, differential train-ing produced a significant divergence in prefer-ence. Birds trained with red showed a significantshift in preference in the direction of red. Birdstrained with blue tended to show increasedpreference for blue on test 2, but the shift ofpreference to blue was statistically significantonly in the exposure group .

In short, all the three training procedureswere successful in producing a divergence of

Red Blue No preference

Exposure 35 16 17

Imprinting 30 19 21

Conditioning 41 12 11

Controls 22 13 5

Total 128 60*** 54

24

10

preference, and (apart from the efficiency ofexposure to blue in the exposure group) noprocedure appeared superior to another in thisrespect .

If control data were ignored, the differencebetween red-training and blue-training mighthave suggested that training with an initially`attractive' colour is more effective in changingpreference than training with an unattractivecolour. However, the control chicks also showeda significant shift towards red on test 2. Thusthe effect, if any, of red-training is unclear ; theeffect of blue-training is at least to prevent ashift towards red .

Experiment 2Methods

The subjects were 132 cobb chicks, of which68 were assigned to a 24-hr exposure group, and64 to a 15-min exposure group. The procedurefor testing, `training', and retesting was similarto that of the exposure group in experiment 1 .Chicks were reared individually in a grey penfor 24 hr, then tested in the runway ; after thisthey were placed in a pen lined with red or withblue, and finally retested in the runway . Chicksin the 24-hr exposure group spent 24 hr in the`exposure' pen with food and water, and werethus retested when 48 hr old ; chicks in the 15-min exposure group spent only 15 min in theexposure pen and they were thus still within the`24-hr' age range when retested. Food andwater were necessary for survival of the 24-hrgroup ; water only was given to the 15-mingroup to provide a similar environment to thatof chicks in the exposure group of experiment 1 .Within each experimental group, half thechicks were trained with red, half with blue .Results

It will be seen from Table III that the initialpreferences (i .e . preference on test l) of birds

5***

18

9

17

26 7***

*** P<0 .001, (all Wilcoxon T, one tailed)The divergence in direction of shift for birds differentially trained is significant beyond 0 . 001 level (X2 test) for each trainingcondition.

in the 24-hr and 15-min groups do not differsubstantially, and do not differ from thoseobtained from the exposure group in experiment1 .

Table IV gives the shifts in preference ob-tained as a result of training. In both experimentsbirds trained with red showed a clear shiftin preference, on test 2, in the direction of thetraining colour. The birds `trained' for 24 hrwith blue shifted somewhat in preference in thedirection of blue ; no similar tendency wasapparent in the birds trained for 15 mins .Considered in conjunction with data fromexperiment 1, these results indicate that theduration of exposure, at any rate to an initiallyattractive colour, does not affect the magnitudeof the shift in preference which results from it ;

Table III. Initial Preferences of Birds in Experiment 2

* *Divergence from chance distribution : P<0-005 (X2 test)

Table IV. Shift in Preference of Birds in Experiment 2

24 hr exposure

15 min exposure

Shift to R Shift to B Shift toR Shift to B

(*) P = 0 .07, **P<0 .005, ***P<0 . 001 (all WilcoxonT, one tailed)

The divergence in direction of shift for birds differ-entially trained is significant (X2 test) : 24 hr, P<0 . 001 ;15 min, P<0 . 05 .

TAYLOR et al. : CHANGING COLOUR PREFERENCES OF CHICKS 5

Table II. Shift in Preference of Birds in Experiment 1

Exposure Imprinting Conditioning Control

Shift Shift Shift

Shift Shift Shift Shift Shiftto R to B to R

to B to R to B to R to B

Red Blue No preference

24 hr exposure 38 17 14

15 min exposure 23 15 24

Total 61 32** 38

Red-trained 25 4*** 21 6**

Blue-trained 13 19(*) 12 13

Red-trained 19 4**

Blue-trained 8 20*

(*) 0 .05<P<0.052 ; * P<0 . 05 ; ** P<0 . 005 ;

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ANIMAL BEHAVIOUR, 17, 1

in the case of blue-training there may be a differ-ence in efficiency between 15 min exposure and2 hr exposure, but no substantial differencebetween 2 hr and 24 hr (the latter producingrather less evidence of shift than the former) .Since the age of chicks at test 2 varies with theexposure time employed, it is difficult to drawvery firm conclusions from these rather slightdifferences among chicks exposed for 15 min,2 hr and 24 hr .

Experiment 3Methods

116 cobb chicks served as subjects, 68 ofthem being assigned to the experimental groupand 48 to the control group. For the experi-mental chicks the procedure was identical to thatof the exposure group in experiment 1, exceptthat the colours used were now blue and yellow(ICI Perspex Sheet 250) rather than blue and red .Thus, the chicks were individually reared ingrey pens, tested when 24 hr old in a runwaywith yellow at one end and blue at the other,placed for 2 hr in a pen lined either with yellowor with blue, and retested in the runway. Thecontrol chicks were tested similarly but spentthe 2 hr between test 1 and test 2 in a grey pen .A chick was assigned a positive score if it wasmore often observed near the yellow end of therunway during testing, and, as before, a negativescore if more time was spent at the blue end .Results

Chicks in both groups showed an initialpreference for yellow over blue, as seen inTable V .Table V. Initial Preferences of Domestic Chicks in

Experiment 3

***Divergence from chance distribution : P<0 . 001(X2 test)

Table VI gives the shifts in preference ob-served in experimental and control groups .The effects in the experimental group weresimilar to those of experiment 1, but in generalless clear-cut ; birds trained with yellow (aninitially attractive colour) shifted in preferencetowards yellow on test 2, while birds trainedto blue did not shift in the direction of thetraining colour . The control chicks, in contrast

to the control chicks of experiment 1, showed noshift in preference between test 1 and test 2 .

Experiment 4Methods

The subjects employed were 63 Japanesequail chicks, 32 of these in the experimentalgroup and 31 in the control group .

For practical convenience the quail chickswere reared in small groups until testing when4 to 7 days old . The rearing pens were brown incolour and one ft 2 (30 cm 2 ) and were similar tothose used for the domestic chicks ; food andwater were provided .

The quail were tested in the runway with redand blue, behaviour being observed and scoredas in previous experiments . Chicks in experi-mental groups were then placed for 2 hr in apen lined with red or with blue ; control chickswere placed in a brown pen for the same period,and after this period each chick was retested .Results

There is no very clear preference for red overblue on test I (see Table VII) .

From Table VIII it will be seen that birds inthe experimental group, whether trained withred or with blue, showed a significant shift inpreference towards the training colour ; thecontrol chicks showed no consistent shift fromtest 1 to test 2 .Discussion

It is evident that preference of domestic-fowlTable VI. Shift in Preference of Birds in Experiment 3

Experimental

Control

Shift to Y Shift to B Shift to Y Shift to B

Yellow-trained

17

7*

Blue-trained

13

1619

18

*P = 0 .0505 (Wilcoxon T, one-tailed)The divergence of shift in preference for differentially

trained birds approaches significance (X2 test) P<0 . 05)

Table VII . Initial Preferences of Japanese Quail inExperiment 4

*No significant divergence from chance distribution

Red Blue No preference

Experimental 16 12 4

Control 17 9 5

Total 33 21 * 9

Yellow Blue No preference

Experimental 35 17 16

Control 26 10 12

Total 61 27*** 28

Red-trained

13

Blue-trained

3

12**

TAYLOR et al. : CHANGING COLOUR PREFERENCES OF CHICKS

7

Table VM. Shift in Preference of Quail Chicks inExperiment 4

Experimental

Control

Shift to R Shift to B Shift to R Shift to B

3**13

16

**P<0 .005 (Wilcoxon T, one-tailed)The divergence in shift of preference for differentially

trained birds is significant beyond 0 . 01 (X2 test)or quail chicks between two colours can bemodified in favour of one of these colours byexposure to it. Where the two colours are notinitially equally attractive the effects of exposureappear to be asymmetrical; there is a moremarked shift towards the initially preferredcolour (as a result of exposure) than towards thenon-preferred colour. As far as experiment 1 isconcerned, since control chicks as well as red-trained chicks show a clear shift in preferencetowards red on a second test, it is the behaviourof blue-trained chicks in showing no such shiftthat provides evidence of the efficacy of train-ing. This might suggest that training with aninitially unattractive colour is more effectivein modifying preference ; and Taylor et al.(1967) have reported that the texture preferencesof domestic chicks appear to be influencedmore by exposure to an initially non-preferredtexture than by exposure to a preferred texture .However, the results of experiment 3 do notsupport this conclusion ; in this case a shifttowards yellow, the initially preferred colour,occurs only in yellow-trained birds and not incontrols, while control and blue-trained chicksare alike in showing no shift. Clearly furtherstudies are need to clarify the interpretation ofour findings. It appears that the asymmetryin the effects of training is to be attributed to thedifferential attractiveness of the colours used ;the Japanese quail chicks, which exhibited noclear initial preference for one colour over theother, showed a clear shift of preference in thedirection of the `exposure' colour, whether thiswas red or blue.

From consideration of experiments 1 and 2together it appears that the effect of exposureis not dependent upon the exposure time allowed ;there is virtually no difference in the magnitudeof the shifts brought about by 15 min, 2 hr or 24hr exposure. There are of course other variablesconfounded with that of exposure time, for

example age of the chicks at test 2, the timeelapsing between tests, the presence of foodand water during 24 hr exposure and of wateralone during 15 min or 2 hr exposure. Hence,while these variables do not a priori suggesteffects which might systematically obscure someeffect of exposure time, we cannot state withcertainty that the duration of exposure (abovesome minimum time which is briefer than anywe have used) is unimportant for the modi-fication of preference . It may well be, for ex-ample, that the shift of preference brought aboutby a longer exposure time, if not greater inextent, may be better retained. We are at presentinvestigating the effect of varying exposure timeupon the retention of preferences acquiredthrough exposure.

Finally, the results of experiment 1 showthat no one training procedure of the three used-exposure, imprinting, or conditioning-emerges as superior to the rest ; all are similarin their effects. How these procedures are relatedto one another may be described in a numberof ways. It could be argued that our exposuretraining is a form of imprinting ; imprintinghas been shown to occur to stationary as well asto moving objects (e.g. Abercrombie & James,1961), and exposure training resembles classicalimprinting in procedure more closely than itresembles classical or instrumental conditioning .It is then interesting to note that imprintingprocedures, commonly held to be independentof conventional reward, are as effective inmodifying behaviour as is a conditioning pro-cedure which systematically rewards selectionof one stimulus value rather than another .A second view relating these procedures

might be that all are essentially reward learning ;since water was present in exposure and im-printing pens, drinking might be held to havereinforced proximity to the colour predominantin the pen. If this interpretation is acceptedthen it is curious that 24 hr exposure with foodas well as water did not produce clearer evidenceof shift than, say, 2 hr exposure with wateralone; and, again, that the more systematicand discriminative reinforcement of the con-ditioning procedure did not prove superior inmodifying performance . We are not specificallyconcerned to deny the importance of convention-al reward in exposure and imprinting pro-cedures, although there is evidence that thepresence or absence of water in the trainingpen does not affect the efficiency of imprinting(Taylor & Sluckin, 1964) . There is however a

8

final basis for comparison of our training pro-cedures. All have in common that they bringthe animal into proximity with one colourrather than another, whether this end is achievedby confinement in a coloured pen, by imprintingto a moving coloured object, or by coupling acolour with heat . It might be argued that thedevelopment or modification of preference isattained by exposure to a given colour or othercharacteristic, and that all our procedures areeffective in so far as they control the proximityof chick and colour. Thus, `reinforcementtraining' might be regarded as the vehicle forexposure learning, rather than the reverse .Clearly, however, such a conclusion, whilesuggested by our findings, would have to relyon weightier evidence .

SummaryDomestic fowl and Japanese quail chicks werefirst tested individually for approach choicebetween two colours, and, after some experienceof one or the other colour or neither, wereagain tested for choice between the same colours .In two experiments domestic chicks were givenas `training' experience 2 hr of exposure tocoloured walls of a pen, or 2 hr conventionalimprinting to a coloured object, or 2 hr con-ditioning in which heat was used as UCS andcolour as CS. All methods were found to beeffective in influencing the chicks' preference .In another experiment, using the exposuremethod only and different durations of exposure,it was found that 15 min was not much lesseffective than 24 hr in modifying the chicks'

ANIMAL BEHAVIOUR, 17, 1

colour choices . In a further experiment quailchicks were used ; although their initial prefer-ences were not quite like those of domesticchicks, these preferences were at least as readilymodifiable .

REFERENCESAbercrombie, B. & James, H. (1961) . The stability of

the domestic chick's response to visual flicker .Anim. Behav., 9, 205-212 .

Gray, P. H . (1961) . The releasers of imprinting : differ-ential reactions to color as a function of matur-ation. J. comp . physio!. Psycho!., 54, 597-601 .

Kear, J. (1964) . Colour preference in young anatidae .Ibis, 106, 361-369.

Kear, J . (966) . The pecking response of young CootsFalica atra and Moorhens Gallinula chloropus.Ibis, 108, 118-122 .

Lashley, K . S. (1916) . Color vision in birds . I . The spec-trum of the domestic fowl . J. Anim. Behav., 6,1-26.

Schaefer, H. H . & Hess, E. H . (1959) . Color preferencesin imprinting objects . Z. Tierpsychol., 16,161-172.

Smith, F . V. & Hoyes, P. A. (1961) . Properties of thevisual stimuli for the approach response in thedomestic chick . Anim. Behav., 9, 159-166 .

Smith, T. L. & Meyer, M . E . (1965) . Preference of chicksin the original stimulus situation of imprinting .Psychonom . Sci., 2, 121-122 .

Taylor, A ., Sluckin, W ., Hewitt, R . & Guiton, P . (1967).The formation of attachments by domestic chicksin two textures. Anim. Behav., 15, 512-517 .

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

Thorndike, E . L . (1911) . Animal Intelligence . New York :Macmillan .

Weidmann, U. (1965) . `Colour preference' and peckingresponse of young Moorhens Gallinula chloropusand Coots Fulica atra . Ibis, 107, 108-110 .

(Received 7 September 1967 ; revised 14 February 1968 ;Ms. number : 773)