The Role of Auditory Stimulation in Responsiveness in Young Chicks CATHRYN P. BROWN School of Behavioural Sciences Macquarie University North Ryde, New South Wales Australia The mechanism of action of the auditory signal in increasing responsiveness to a visualauditory stimulus in chicks of 14-48 hr was examined. Stimulus effectiveness of an at ditory signal dissociated from the visual stimulus was less than proximate auditory signal presentation but greater than a silent visual stimulus. Familiarity with the auditory signal increased and decreased responding under proximate and dissociated presentation, respectively. These data were interpreted as confirming the influence of auditory stimulation via increased arousal, and as indicating the possibility of selective responding to specific features of the auditory stimulus when its localization at the visual stimulus is possible.
Several aspects of auditory stimulation have been emphasized in accounting for facilitation of imprinting and early approach in young chicks and ducklings: First, auditory stimulation may enhance the attentional value of and, thus, orientation to the visual stimulus (Klopfer & Gottlieb, 1962). Second, it may increase the level of general arousal in the chick independent of any such change in target impact (Pitz & Ross, 1961)-a phenomenon of demonstrated importance in imprinting (e.g., Boyd & Fabricius, 1965; Candland, Nagy, & Conklyn, 1963; Fischer, 1970, 1972; Kovach, 1964; Kovach & Hess, 1963; Moltz, Rosenblum, & Halikas, 1959; Porter & Stettner, 1971; Rajecki & Saegert, 1971; Sluckin & Salzen, 1961). Third, the auditory component itself may be attended to, responded to, and learned just as effectively as the visual component (Fischer, 1966). Consistent with this last emphasis is the evidence for “naive” preferences for certain sounds (Gottlieb, 1965, 1966, 1971), and the observation that birds respond to sounds alone (Collias, 1952; Smith & Bird, 1964) and that responsiveness to sounds can be altered by previous experience (Fischer, 1966; Klopfer, 1959a,b; Ramsay, 1951) as with visual stimuli (e.g., Broom, 1969; Reese, SchottC, Bechtold, & Cowley, 1972). This study examined the influence on responsiveness of the potential effects of the auditory component of an auditory-visual stimulus. The relative influence of the Request reprints from: Dr. Cathryn P. Brown, School of Behavioural Sciences, Macquarie University, North Ryde, New South Wales 21 13, Australia. Received for publication 21 August 1975 Revised for publication 29 December 1976 Developmental Psychobiology, 1O(1): 33-40 (1 977) @ 1977 by John Wiley & Sons, Inc.
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general arousal and specific target-orienting functions of the sound was assessed by comparing responsiveness using “generalized” auditory stimulation dissociated from the visual stimulus, and using a sound source associated with and proximate t o that stimulus. Both presentation methods would be equally effective if sound simply increased arousal independent of any effect on the target value of the visual stimulus. But if sound functions by enhancing orientation t o the visual stimulus, responsiveness to that stimulus would be greater when the sound can be localized and is proximate t o the stimulus. Further, the emphases on general arousal and on enhanced orientation both suggest that qualitatively different sounds, similar in attentional value t o naive chicks, would be equally effective in increasing responsiveness. Previous experience with a certain sound-unless that experience decreased the sound’s novelty value and thus its arousal or attentional impact, leading to decreased responsiveness-would not otherwise influence the impact of the sound. On the other hand. the 3rd emphasis-that chicks respond to and learn specific features of the auditory signal-suggests that i n accordance with other observations (Fischer, 1966; Ramsey, 195 1 ) previous exposure should further increase responsiveness to a particular sound. Such an increase would only be apparent when localization of the sound is possible in that generalized presentation should show n o overall effect on responsiveness. If proximate to the visual stimulus, responsiveness t o that stimulus would be thereby increased, more appreciably by a familiar than by an unfamiliar sound.
Method Subjects Four hundred and fifty White-Leghorn x Black Orpington eggs (Gallus domesticus) were obtained from a local hatchery and incubated and hatched in hobby incubators set at 36°C in the laboratory. Immediately after hatching, chicks were placed in individual cardboard boxes, each measuring 15 x 15 x 15 cni; the lids of each were perforated by 20 small air holes. The floor of each compartment was spread with crumpled, dampened paper towels and the boxes were placed in large aluminium tubs, each tub covered b y a commercial hobby-brooder which maintained the temperature within the tub at approximately 30°C. All boxes were numbered and times of hatching recorded.
Apparatus Testing for initial approach and following to the test stimulus was carried out in a small sealed chamber 2 x 2 x 2 in with the floor marked into 36 equal squares. A television camera fitted t o the ceiling of the chamber transmitted t o a closed circuit video monitor located in an adjacent room. The test stimulus was a red cardboard cylinder, 15 cni in diatneter and 20 cm high, placed over a movable platform of similar diameter. The platform, driven by a sinall motor, was under remote control and could be maneuvered-along with the cylinder-right, left, or forward. Speed of movement was fixed at approximately 8 cm/sec; the pattern of movement was a set sequence, 3 sec t o the right-3 sec t o the left, such that the cylinder traced a zig-zag path during testing. This procedure was adopted in view of the reported effectiveness of lateral movement in
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inducing approach and following of visual stimuli (Smith, 1960). For proximate stimulus presentation a small receiver/speaker was set on the roof of the cylinder through which a continuous tape of the brooding cackles of a hen at the local hatchery, or of a sequence of young chick twitters (Collias & Joos, 1953) could be played. For dissociated presentation, these same tapes, derived from hens or from the chicks themselves, were played through a speaker located 3.5 m above in the ceiling of the test chamber. The loudness of the hen tape was reduced to that of the chick tape, the actual calls on each ranging between 60 and 70 dB on the B scale of a General Radio sound level meter. This amplitude was constant at all points in the chamber under both presentation methods. Preliminary studies with 15 naive chicks showed no difference between the tapes in latency to approach these sounds. Such a result suggests that these particular calls differed from the stimuli used by Gottlieb (1965, 1966, 1971) in his demonstration of “naive” selective responsiveness with preferences apparent for the maternal “exodus” call in young chicks. Possible attempts to localize the sound source under the generalized presentation and orient to it rather than to the visual signal were not considered significant to the purposes of t h s study. First, such localization was particularly difficult in view of the distance of the sound from the chick and the high reflectance within the chamber. Second, even were such localization attempted, the interpretation of the results in relation to the 3 emphases outlined above would be nevertheless unaffected. The temperature within the sealed chamber was maintained a t approximately 28°C by placing an electric heater inside the chamber for 10 min prior to testing each chick. Although the heater was removed during testing, the temperature was found to drop no more than 3°C during the test session.
Proced Lire Testing. At the start of the test period, individual clucks were removed by hand from their boxes and placed into the center of the marked field in the same square as the stimulus and facing the stimulus. The test session involved an initial 10-min adaptation exposure to the stimulus which each 2.5 min made 4 single circling movements out of the square and back to whichever square the chick was located. (The reduced initial mobility of the stimulus was found more effective in eliciting approach than initially sustained movement.) Subsequently, the cylinder was moved once each minute out of and back t o the chick’s square. The chick was scored as approaching when it crossed the line between its square and the square in which the stimulus was located. The average latency t o approach was calculated for each group. The session lasted no more than 30 min. Rearing. Two studies differing only in auditory stimulation during rearing were conducted and analyzed separately. Separate analyses were carried out in view of (1) the complexity of variables involved and (2) the fact that actual differences between the rearing treatments were irrelevant to the main questions considered in the study. In Experiment 1 , 225 chicks were reared from hatching until testing with a continuous tape of hen cackles, similar t o the subsequent hen-noise test tape. In Experiment 2 a continuous tape of chick twitters, similar to the chick-noise test tape presentation, was played throughout rearing. The sound was diffuse in presentation, located at the opposite end of the room from the ckicks, and equivalent in amplitude for all.
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Although self-produced chick twitters might have been heard by the hen-reared birds, continuous observation and recording indicated negligible vocalization by this group during rearing. (Hen noise appeared to reduce markedly the general level of vocaliLation in this group.) In both experiments, each chick after hatching was assigned in order to 1 to I 5 groups ( I 5 chicks per group.)
Resuit s Auditory stimuli were generally confirmed as more effective than the silent stimulus after both chick ( F = 7 . 3 6 , d f = 1/210, p < .01) and hen noise ( F = 8 . 2 3 , d f = 1/210, p < . O l ) , but the extent of this improvement did not increase with test age. Age decreased responsiveness following rearing with either chick ( F = 7.08, d f = 1/140, p < .01) or hen noise ( F = 7 . 5 1 , d f = 1/140, p < .01). The effect was linear: the decrease was similar between 1 6 and 32 hr and 32 and 48 hr posthatching. Dissociated presentation was less effective than proximate after hen rearing ( F = 4.02, df= 1/168, p < .05) but not chick rearing though the trend was in that direction. Lack of significance in this effect was due t o the interaction between presentation method and degree of familiarity, discussed below. The effect of presentation method was constant with test age. No overall difference appeared in either experiment between the familiar and unfamiliar stimuli. Familiarity, however, did differentially affect the change in responsiveness with increased test age. The decline in responsiveness t o unfamiliar stimuli (marked UF) contrasted with apparent constancy of effectiveness of familiar stimuli (marked F) at all test ages (see Fig. I ) . This interaction was significant after both chick ( F = 12.25, df= 1/168, p < .001) and hen noise ( F = 13.84, d f = 1/168, p < .001). The lack of significance of familiarity in influencing overall responsiveness was due to the significant interaction between presentation method and stimulus familiuity after both chick ( F z 8 . 1 1 , d f = 1 / 1 6 8 , p. C a, Y
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Fig. 1. Approach latencies following rearing under (a) and (b) chick noise conditions.
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Additionally, these results have some bearing on a number of recent interpretations of what is generally accepted as the imprinting process, although not bearing upon the more basic and perhaps insoluble problem of whether such modifications or extensions of responsiveness are tapping some phenomenon other than “pure” imprinting as Hcss (1973) maintains. First, heightened responsiveness to dissociated auditory stimulation compared with that to silent stimuli confirms the view (Pitz & Ross, 1961) that heightened general arousal induced by auditory stimulation, independent of any change in the attentional value of the stimulus itself, may be responsible in part for increased responsiveness t o visual/auditory signals. Furthermore the relatively greater effectiveness of unfamiliar rather than familiar stimuli undcr dissociated presentation is consistent with such an interpretation. Novel stimuli might be expected to produce a greater increase in arousal than familiar sounds. In short, when localization of the auditory signal at the visual stimulus is not possible, auditory stimulation nevertheless can influence responsiveness, primarily via heightening arousal. Of more general theoretical significance, and consistent with several previous reports (Boyd & Fabricius, 1965; Fischer, 1970; Porter & Stettner, 1971; Rajecki & Saegert, l971), this finding confirms that arousal, produced independent of any change in the stimulus itself, can influence responsiveness. Thus, this result provides further evidence against the view that imprinting depends simply upon the complexity, impact, or attentional value of the target as proposed in the “infor mat ion processing” account of imprinting (Matt hews & Hemmings, 1963). The 2nd main finding, that proximate presentation tends t o be more effective than dissociated presentation, indicates that when possible the auditory component may exert ;1 still more marked influence on responsiveness via a mechanism more specific than that of general arousal. Whereas this mechanism may relate t o the role of the sound in stimulus orientation, increasing the attentional value of the target (Pitz & Ross, 1961), certain aspects of the results suggest that this is not the case. The effect is niore probably dependent upon the 3rd mechanism of action mentioned above, i.e., responsiveness t o specific characteristics of the auditory stimulus itself. Most relevant is the increase in responsiveness t o familiar rather than unfamiliar stimuli when localization is possible as confirmed by the significant interaction between nature of stimulus and method of presentation. Such a result is inconsistent with the stimulus orienting analysis and the more general information processing interpretation of imprinting (Matthews & Hemrnings, 1963). According t o such accounts, unfamiliar stimuli would have greater impact due t o their novelty and should thus be more effective than the familiar stimuli in enhancing responsiveness. On the other hand this finding does confirm the proposal of selective responsiveness t o the auditory signal (Fischer, 1966) and has further bearing upon several other general accounts of imprinting. The actual prediction of facilitated responsiveness with familiar stimuli was based not only on the proposal that chicks will respond t o and learn specific features of the auditory signal, but also on 2 assumptions (thereby also confirmed) derived from a n epigenetic analysis (Kovach, 1970). (1) Stimuli of relatively high intensity will be effective with young chicks in eliciting approach and imprinting, but as endogenous arousal increases with age, stimuli eliciting lower levels of arousal will become niore effective. (2) In common with the interpretations mentioned above, the more familiar the stimulus, the lower the level of arousal produced. Thus, in this study that t-csponsiveness t o familiar stimuli showed no decline with age, in contrast t o the
AUDITORY STIMULATION AND RESPONSlVENESS
39
progressively reduced effectiveness of unfamiliar stimuli, is particularly significant. The present findings provide further support for this epigenetic interpretation, in common with several previous reports of similarly facilitated and extended responsiveness to familiar stimuli, whether these stimuli be auditory (Fischer, 1966; Klopfer, 1959a,b; Ramsey, 1951) or visual (e.g., Broom, 1969; Reese et al., 1972). However, the present findings indicate the greater usefulness of an alternative account of imprinting as outlined by Rajecki (1973), based on the neuronal model interpretation (Sokolov, 1963) offered by Salzen (1962, 1970): Within limits a chick will approach a stimulus, first, to the extent that it leads to a decrease in the orienting reflex to the environment and, thereby, in the noxious state of arousal produced. In older birds habituation will be more rapid to more familiar stimuli. In young birds the difference between familiar and novel stimuli will be less marked due to the absence of a complete neuronal model of the environment against which to compare incoming stimulation. In the present study, this is confirmed in the relatively and progressively greater effectiveness of familiar stimuli when localization is possible. Second, responsiveness is also increased to the extent that the state of habituation to the stimulus is preferable to the state of arousal produced by other unfamiliar aspects of the environment. The 2nd finding of this study, the potential facilitation of responsiveness with increments in general arousal produced under dissociated auditory stimulation despite an unchanged target, can be thereby accommodated within this framework. Although, as Rajecki (1973) notes, further research involving independent measurement of arousal during imprinting is necessary for confirmation of this general approach, such an analysis seems most useful at present in the light of these findings.
Notes This study was assisted by a Macquarie University Research Grant.
References Boyd, H., and Fabricius, E. (1965). Observations on the incidence of following and visual and auditory stimuli in naive mallard ducklings. Behaviour, 25: 1-15. Broom, D. M. (1969). Effects of visual complexity during rearing on chicks’ reactions to environmental change. Anim. Behav., 1 7 773-780. Candland, D. K., Nagy, Z. M., and Conklyn, D. H. (1963). Emotional behaviour in the domestic chicken (White Leghorn) as a function of age and developmental environment. J. Comp. Physiol. Psychol., 56: 1069-1073. Collias, N. E. (1952). The development of social behaviour in birds. Auk, 6Y: 127-159. Collias, N. E., and Joos, M. (1953). The spectrographic analysis of sound signals in the domestic fowl. Behaviottr, 5: 175-1 89. Fischer, G. J . (1966). Auditory stimuli in imprinting. J. Comp. Physiol Psychol., 61: 271-273. Fischer, G. J . (1970). Arousal and impairment: Temperature effects on following during imprinting. J. Comp. Physiol. Psychol., 73: 412-420. Fischer, G. J. (1972). Sound stimuli and following in a domestic fowl: Frequency, rate and duration. J. Comp. Physiol. Ps.ychol., 81: 183190. Gottlieb, G. (1965). The question of imprinting in relation to parental species identification by avian neonates. J. Comp. Physiol. Psychol., 59: 345-356.
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Gottlieb, G. (1966). Species identification by avian neonates: Contributory effect of pcrinatal auditory stimulation. Anirn. Behav., 1 4 : 282-290. Gottlieb, C;. (1971). Development of Species Identification in Birds. Chicago: University of Chicago Press. Hess, I:. [I. (1973). Imprinting. Ear1.v Experience and the Developmental P ~ c h o b i o l o g v of Attachment. New York: Van Nostrand Rheinhold. Klopfer, P. H. (1959a). An analysis of learning in young Anatidae. Ecology, 40:90-102. Klopfer, P. 1-1. (1959b). The development of sound signal preferences in ducks. Wilson Bull., 71: 262-266. Klopfer, P. II., and Gottlieb, G. (1962). Imprinting and behavioral polyinorphsm: Auditory and visual imprinting in domestic ducks (Anas platyvhynchos) and the involvemcnt of the critical siol. Psychol., 55: 126-1 30. fects of autonomic drugs on imprinting. .J. Comp. Physiol. P~~c.ho1.. 57: 183-187. Kovach. J . K. (1970). Critical period or optimal arousal? Early approach behavior as ;I function of stimulus, age, and breed variables in chicks. Dev. Psychol., 3: 73-77. Kovach, J . K., and Hess, E. H. (1963). Imprinting: Effects of painful stirnulaticin upon the following responsc. J. Comp. Physiol. Psychol., 56: 461-464. Matthcws, W. A., and Hemmings, G. (1963). A theory concerning imprinting. Nature (1-ond.), / W : 1183-1 184. Moltz, H., Rosenblum, L., and Halikas, N. (1959). Imprinting and level of anxiely. J. Comp. Ph.vsiol. Psychol., 52: 240-244. Pitz, C. F., and Ross, R. B. (1961). Imprinting as a function of arousal. J. Comp. Physiol. P.syChOl., 54: 602-604. Portcr, R . H., and Stettner, L. J. (1971). Non-specificity of the following response in Peking ducklings. Percept. Mot. Skills, 33: 27-33. Rajccki, D. W. (1973). Imprinting in prccocial birds: Interpretation, evidcnce, and evaluation. P s . v c ~ o ~Bull., . 79: 48-58. Kajecki, D. W., and Saegcrt, S. (1971). Effects of methamphetamine hydrochloride on irnprintinp in White Leghorn chicks. Psychonom. Sci., 23: 7-8. Kamsay, A. 0. (1951). Familial recognition in domectic birds. Auk, 68: 1-16. Kecre, I:. P., Schotte, C. S., Rechtold, K. E., and Cowley, V. L. (1972). Initial preference of chicks from five rearing conditions for a hen or rotating light. J. Comp. Physiol. P.q~chol.,8/:76-83. Salzen, 1;. 4.(1962). Imprinting and fear. Symp. Zool. Soc. Lorzd., 8 : 199-217. Salzen, I:. A . (1970). lmprinting and environmental learning. In L. R. Aronson, 1:. Tobach, I). S. Lehrman, and J. S. Rosenblatt (Eds.), Development and Evolution of Behavior. %in 1:ranrisco: Frcernan. Pp. 158-178, Sluckin, W., and Salzen, F.. A. (1961). Imprinting and perceptual learning. Q. J. Exp. Pq~chol..13: 65-77. Smith, 1:. V. (1960). Towards a definition of the stimulus situation for the approach response of the domestic chick. Anim. Behai’., 8 : 197-200. Smith, I:. V. and Bird, M. W. (1963). The relative attraction for the domestic of combinations of stimuli in different sensory modalities. Anirn. Rehav., I I : 300-305. Smith, I:. V., and Bird, M. W. (1964). The correlation of responsiveness to visual and auditory stimuli in the domestic chick. Anim. Behav., 1 2 : 259-263. Smith, I:. V., and Nott, K. 1-1. (1970). The “critical period” in relation to the strength o f the stiniuluv. %. Tierpsjdiol., 27: 1 OX-1 15. Sokolov, I:. M. (1963). Perception and the Conditioned Reflex. Oxford: I’ergamon. (Trans. by S. W. Waydenfeid.)
Several aspects of auditory stimulation have been emphasized in accounting for facilitation of imprinting and early approach in young chicks and ducklings: First, auditory stimulation may enhance the attentional value of and, thus, orientation to the visual stimulus (Klopfer & Gottlieb, 1962). Second, it may increase the level of general arousal in the chick independent of any such change in target impact (Pitz & Ross, 1961)-a phenomenon of demonstrated importance in imprinting (e.g., Boyd & Fabricius, 1965; Candland, Nagy, & Conklyn, 1963; Fischer, 1970, 1972; Kovach, 1964; Kovach & Hess, 1963; Moltz, Rosenblum, & Halikas, 1959; Porter & Stettner, 1971; Rajecki & Saegert, 1971; Sluckin & Salzen, 1961). Third, the auditory component itself may be attended to, responded to, and learned just as effectively as the visual component (Fischer, 1966). Consistent with this last emphasis is the evidence for “naive” preferences for certain sounds (Gottlieb, 1965, 1966, 1971), and the observation that birds respond to sounds alone (Collias, 1952; Smith & Bird, 1964) and that responsiveness to sounds can be altered by previous experience (Fischer, 1966; Klopfer, 1959a,b; Ramsay, 1951) as with visual stimuli (e.g., Broom, 1969; Reese, SchottC, Bechtold, & Cowley, 1972). This study examined the influence on responsiveness of the potential effects of the auditory component of an auditory-visual stimulus. The relative influence of the Request reprints from: Dr. Cathryn P. Brown, School of Behavioural Sciences, Macquarie University, North Ryde, New South Wales 21 13, Australia. Received for publication 21 August 1975 Revised for publication 29 December 1976 Developmental Psychobiology, 1O(1): 33-40 (1 977) @ 1977 by John Wiley & Sons, Inc.
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general arousal and specific target-orienting functions of the sound was assessed by comparing responsiveness using “generalized” auditory stimulation dissociated from the visual stimulus, and using a sound source associated with and proximate t o that stimulus. Both presentation methods would be equally effective if sound simply increased arousal independent of any effect on the target value of the visual stimulus. But if sound functions by enhancing orientation t o the visual stimulus, responsiveness to that stimulus would be greater when the sound can be localized and is proximate t o the stimulus. Further, the emphases on general arousal and on enhanced orientation both suggest that qualitatively different sounds, similar in attentional value t o naive chicks, would be equally effective in increasing responsiveness. Previous experience with a certain sound-unless that experience decreased the sound’s novelty value and thus its arousal or attentional impact, leading to decreased responsiveness-would not otherwise influence the impact of the sound. On the other hand. the 3rd emphasis-that chicks respond to and learn specific features of the auditory signal-suggests that i n accordance with other observations (Fischer, 1966; Ramsey, 195 1 ) previous exposure should further increase responsiveness to a particular sound. Such an increase would only be apparent when localization of the sound is possible in that generalized presentation should show n o overall effect on responsiveness. If proximate to the visual stimulus, responsiveness t o that stimulus would be thereby increased, more appreciably by a familiar than by an unfamiliar sound.
Method Subjects Four hundred and fifty White-Leghorn x Black Orpington eggs (Gallus domesticus) were obtained from a local hatchery and incubated and hatched in hobby incubators set at 36°C in the laboratory. Immediately after hatching, chicks were placed in individual cardboard boxes, each measuring 15 x 15 x 15 cni; the lids of each were perforated by 20 small air holes. The floor of each compartment was spread with crumpled, dampened paper towels and the boxes were placed in large aluminium tubs, each tub covered b y a commercial hobby-brooder which maintained the temperature within the tub at approximately 30°C. All boxes were numbered and times of hatching recorded.
Apparatus Testing for initial approach and following to the test stimulus was carried out in a small sealed chamber 2 x 2 x 2 in with the floor marked into 36 equal squares. A television camera fitted t o the ceiling of the chamber transmitted t o a closed circuit video monitor located in an adjacent room. The test stimulus was a red cardboard cylinder, 15 cni in diatneter and 20 cm high, placed over a movable platform of similar diameter. The platform, driven by a sinall motor, was under remote control and could be maneuvered-along with the cylinder-right, left, or forward. Speed of movement was fixed at approximately 8 cm/sec; the pattern of movement was a set sequence, 3 sec t o the right-3 sec t o the left, such that the cylinder traced a zig-zag path during testing. This procedure was adopted in view of the reported effectiveness of lateral movement in
AUDITORY STIMULATION AND RESPONSIVENESS
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inducing approach and following of visual stimuli (Smith, 1960). For proximate stimulus presentation a small receiver/speaker was set on the roof of the cylinder through which a continuous tape of the brooding cackles of a hen at the local hatchery, or of a sequence of young chick twitters (Collias & Joos, 1953) could be played. For dissociated presentation, these same tapes, derived from hens or from the chicks themselves, were played through a speaker located 3.5 m above in the ceiling of the test chamber. The loudness of the hen tape was reduced to that of the chick tape, the actual calls on each ranging between 60 and 70 dB on the B scale of a General Radio sound level meter. This amplitude was constant at all points in the chamber under both presentation methods. Preliminary studies with 15 naive chicks showed no difference between the tapes in latency to approach these sounds. Such a result suggests that these particular calls differed from the stimuli used by Gottlieb (1965, 1966, 1971) in his demonstration of “naive” selective responsiveness with preferences apparent for the maternal “exodus” call in young chicks. Possible attempts to localize the sound source under the generalized presentation and orient to it rather than to the visual signal were not considered significant to the purposes of t h s study. First, such localization was particularly difficult in view of the distance of the sound from the chick and the high reflectance within the chamber. Second, even were such localization attempted, the interpretation of the results in relation to the 3 emphases outlined above would be nevertheless unaffected. The temperature within the sealed chamber was maintained a t approximately 28°C by placing an electric heater inside the chamber for 10 min prior to testing each chick. Although the heater was removed during testing, the temperature was found to drop no more than 3°C during the test session.
Proced Lire Testing. At the start of the test period, individual clucks were removed by hand from their boxes and placed into the center of the marked field in the same square as the stimulus and facing the stimulus. The test session involved an initial 10-min adaptation exposure to the stimulus which each 2.5 min made 4 single circling movements out of the square and back to whichever square the chick was located. (The reduced initial mobility of the stimulus was found more effective in eliciting approach than initially sustained movement.) Subsequently, the cylinder was moved once each minute out of and back t o the chick’s square. The chick was scored as approaching when it crossed the line between its square and the square in which the stimulus was located. The average latency t o approach was calculated for each group. The session lasted no more than 30 min. Rearing. Two studies differing only in auditory stimulation during rearing were conducted and analyzed separately. Separate analyses were carried out in view of (1) the complexity of variables involved and (2) the fact that actual differences between the rearing treatments were irrelevant to the main questions considered in the study. In Experiment 1 , 225 chicks were reared from hatching until testing with a continuous tape of hen cackles, similar t o the subsequent hen-noise test tape. In Experiment 2 a continuous tape of chick twitters, similar to the chick-noise test tape presentation, was played throughout rearing. The sound was diffuse in presentation, located at the opposite end of the room from the ckicks, and equivalent in amplitude for all.
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Although self-produced chick twitters might have been heard by the hen-reared birds, continuous observation and recording indicated negligible vocalization by this group during rearing. (Hen noise appeared to reduce markedly the general level of vocaliLation in this group.) In both experiments, each chick after hatching was assigned in order to 1 to I 5 groups ( I 5 chicks per group.)
Resuit s Auditory stimuli were generally confirmed as more effective than the silent stimulus after both chick ( F = 7 . 3 6 , d f = 1/210, p < .01) and hen noise ( F = 8 . 2 3 , d f = 1/210, p < . O l ) , but the extent of this improvement did not increase with test age. Age decreased responsiveness following rearing with either chick ( F = 7.08, d f = 1/140, p < .01) or hen noise ( F = 7 . 5 1 , d f = 1/140, p < .01). The effect was linear: the decrease was similar between 1 6 and 32 hr and 32 and 48 hr posthatching. Dissociated presentation was less effective than proximate after hen rearing ( F = 4.02, df= 1/168, p < .05) but not chick rearing though the trend was in that direction. Lack of significance in this effect was due t o the interaction between presentation method and degree of familiarity, discussed below. The effect of presentation method was constant with test age. No overall difference appeared in either experiment between the familiar and unfamiliar stimuli. Familiarity, however, did differentially affect the change in responsiveness with increased test age. The decline in responsiveness t o unfamiliar stimuli (marked UF) contrasted with apparent constancy of effectiveness of familiar stimuli (marked F) at all test ages (see Fig. I ) . This interaction was significant after both chick ( F = 12.25, df= 1/168, p < .001) and hen noise ( F = 13.84, d f = 1/168, p < .001). The lack of significance of familiarity in influencing overall responsiveness was due to the significant interaction between presentation method and stimulus familiuity after both chick ( F z 8 . 1 1 , d f = 1 / 1 6 8 , p. C a, Y
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Fig. 1. Approach latencies following rearing under (a) and (b) chick noise conditions.
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Additionally, these results have some bearing on a number of recent interpretations of what is generally accepted as the imprinting process, although not bearing upon the more basic and perhaps insoluble problem of whether such modifications or extensions of responsiveness are tapping some phenomenon other than “pure” imprinting as Hcss (1973) maintains. First, heightened responsiveness to dissociated auditory stimulation compared with that to silent stimuli confirms the view (Pitz & Ross, 1961) that heightened general arousal induced by auditory stimulation, independent of any change in the attentional value of the stimulus itself, may be responsible in part for increased responsiveness t o visual/auditory signals. Furthermore the relatively greater effectiveness of unfamiliar rather than familiar stimuli undcr dissociated presentation is consistent with such an interpretation. Novel stimuli might be expected to produce a greater increase in arousal than familiar sounds. In short, when localization of the auditory signal at the visual stimulus is not possible, auditory stimulation nevertheless can influence responsiveness, primarily via heightening arousal. Of more general theoretical significance, and consistent with several previous reports (Boyd & Fabricius, 1965; Fischer, 1970; Porter & Stettner, 1971; Rajecki & Saegert, l971), this finding confirms that arousal, produced independent of any change in the stimulus itself, can influence responsiveness. Thus, this result provides further evidence against the view that imprinting depends simply upon the complexity, impact, or attentional value of the target as proposed in the “infor mat ion processing” account of imprinting (Matt hews & Hemmings, 1963). The 2nd main finding, that proximate presentation tends t o be more effective than dissociated presentation, indicates that when possible the auditory component may exert ;1 still more marked influence on responsiveness via a mechanism more specific than that of general arousal. Whereas this mechanism may relate t o the role of the sound in stimulus orientation, increasing the attentional value of the target (Pitz & Ross, 1961), certain aspects of the results suggest that this is not the case. The effect is niore probably dependent upon the 3rd mechanism of action mentioned above, i.e., responsiveness t o specific characteristics of the auditory stimulus itself. Most relevant is the increase in responsiveness t o familiar rather than unfamiliar stimuli when localization is possible as confirmed by the significant interaction between nature of stimulus and method of presentation. Such a result is inconsistent with the stimulus orienting analysis and the more general information processing interpretation of imprinting (Matthews & Hemrnings, 1963). According t o such accounts, unfamiliar stimuli would have greater impact due t o their novelty and should thus be more effective than the familiar stimuli in enhancing responsiveness. On the other hand this finding does confirm the proposal of selective responsiveness t o the auditory signal (Fischer, 1966) and has further bearing upon several other general accounts of imprinting. The actual prediction of facilitated responsiveness with familiar stimuli was based not only on the proposal that chicks will respond t o and learn specific features of the auditory signal, but also on 2 assumptions (thereby also confirmed) derived from a n epigenetic analysis (Kovach, 1970). (1) Stimuli of relatively high intensity will be effective with young chicks in eliciting approach and imprinting, but as endogenous arousal increases with age, stimuli eliciting lower levels of arousal will become niore effective. (2) In common with the interpretations mentioned above, the more familiar the stimulus, the lower the level of arousal produced. Thus, in this study that t-csponsiveness t o familiar stimuli showed no decline with age, in contrast t o the
AUDITORY STIMULATION AND RESPONSlVENESS
39
progressively reduced effectiveness of unfamiliar stimuli, is particularly significant. The present findings provide further support for this epigenetic interpretation, in common with several previous reports of similarly facilitated and extended responsiveness to familiar stimuli, whether these stimuli be auditory (Fischer, 1966; Klopfer, 1959a,b; Ramsey, 1951) or visual (e.g., Broom, 1969; Reese et al., 1972). However, the present findings indicate the greater usefulness of an alternative account of imprinting as outlined by Rajecki (1973), based on the neuronal model interpretation (Sokolov, 1963) offered by Salzen (1962, 1970): Within limits a chick will approach a stimulus, first, to the extent that it leads to a decrease in the orienting reflex to the environment and, thereby, in the noxious state of arousal produced. In older birds habituation will be more rapid to more familiar stimuli. In young birds the difference between familiar and novel stimuli will be less marked due to the absence of a complete neuronal model of the environment against which to compare incoming stimulation. In the present study, this is confirmed in the relatively and progressively greater effectiveness of familiar stimuli when localization is possible. Second, responsiveness is also increased to the extent that the state of habituation to the stimulus is preferable to the state of arousal produced by other unfamiliar aspects of the environment. The 2nd finding of this study, the potential facilitation of responsiveness with increments in general arousal produced under dissociated auditory stimulation despite an unchanged target, can be thereby accommodated within this framework. Although, as Rajecki (1973) notes, further research involving independent measurement of arousal during imprinting is necessary for confirmation of this general approach, such an analysis seems most useful at present in the light of these findings.
Notes This study was assisted by a Macquarie University Research Grant.
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Gottlieb, G. (1966). Species identification by avian neonates: Contributory effect of pcrinatal auditory stimulation. Anirn. Behav., 1 4 : 282-290. Gottlieb, C;. (1971). Development of Species Identification in Birds. Chicago: University of Chicago Press. Hess, I:. [I. (1973). Imprinting. Ear1.v Experience and the Developmental P ~ c h o b i o l o g v of Attachment. New York: Van Nostrand Rheinhold. Klopfer, P. H. (1959a). An analysis of learning in young Anatidae. Ecology, 40:90-102. Klopfer, P. 1-1. (1959b). The development of sound signal preferences in ducks. Wilson Bull., 71: 262-266. Klopfer, P. II., and Gottlieb, G. (1962). Imprinting and behavioral polyinorphsm: Auditory and visual imprinting in domestic ducks (Anas platyvhynchos) and the involvemcnt of the critical siol. Psychol., 55: 126-1 30. fects of autonomic drugs on imprinting. .J. Comp. Physiol. P~~c.ho1.. 57: 183-187. Kovach. J . K. (1970). Critical period or optimal arousal? Early approach behavior as ;I function of stimulus, age, and breed variables in chicks. Dev. Psychol., 3: 73-77. Kovach, J . K., and Hess, E. H. (1963). Imprinting: Effects of painful stirnulaticin upon the following responsc. J. Comp. Physiol. Psychol., 56: 461-464. Matthcws, W. A., and Hemmings, G. (1963). A theory concerning imprinting. Nature (1-ond.), / W : 1183-1 184. Moltz, H., Rosenblum, L., and Halikas, N. (1959). Imprinting and level of anxiely. J. Comp. Ph.vsiol. Psychol., 52: 240-244. Pitz, C. F., and Ross, R. B. (1961). Imprinting as a function of arousal. J. Comp. Physiol. P.syChOl., 54: 602-604. Portcr, R . H., and Stettner, L. J. (1971). Non-specificity of the following response in Peking ducklings. Percept. Mot. Skills, 33: 27-33. Rajccki, D. W. (1973). Imprinting in prccocial birds: Interpretation, evidcnce, and evaluation. P s . v c ~ o ~Bull., . 79: 48-58. Kajecki, D. W., and Saegcrt, S. (1971). Effects of methamphetamine hydrochloride on irnprintinp in White Leghorn chicks. Psychonom. Sci., 23: 7-8. Kamsay, A. 0. (1951). Familial recognition in domectic birds. Auk, 68: 1-16. Kecre, I:. P., Schotte, C. S., Rechtold, K. E., and Cowley, V. L. (1972). Initial preference of chicks from five rearing conditions for a hen or rotating light. J. Comp. Physiol. P.q~chol.,8/:76-83. Salzen, 1;. 4.(1962). Imprinting and fear. Symp. Zool. Soc. Lorzd., 8 : 199-217. Salzen, I:. A . (1970). lmprinting and environmental learning. In L. R. Aronson, 1:. Tobach, I). S. Lehrman, and J. S. Rosenblatt (Eds.), Development and Evolution of Behavior. %in 1:ranrisco: Frcernan. Pp. 158-178, Sluckin, W., and Salzen, F.. A. (1961). Imprinting and perceptual learning. Q. J. Exp. Pq~chol..13: 65-77. Smith, 1:. V. (1960). Towards a definition of the stimulus situation for the approach response of the domestic chick. Anim. Behai’., 8 : 197-200. Smith, I:. V. and Bird, M. W. (1963). The relative attraction for the domestic of combinations of stimuli in different sensory modalities. Anirn. Rehav., I I : 300-305. Smith, I:. V., and Bird, M. W. (1964). The correlation of responsiveness to visual and auditory stimuli in the domestic chick. Anim. Behav., 1 2 : 259-263. Smith, I:. V., and Nott, K. 1-1. (1970). The “critical period” in relation to the strength o f the stiniuluv. %. Tierpsjdiol., 27: 1 OX-1 15. Sokolov, I:. M. (1963). Perception and the Conditioned Reflex. Oxford: I’ergamon. (Trans. by S. W. Waydenfeid.)
