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Meltzoff___Moore_1977

Meltzoff___Moore_1977 - References and Notes 1 M Buchsbaum...

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Unformatted text preview: References and Notes 1. M. Buchsbaum and J. Silverman, Psychosom. Med. 30, l2 (1968); J. Silverman. M. Buchs- baum. R. I-Ienkin, Percept. Mot. Skills 28, 71 (1969). 2. M. Buchsbaum and A. Pfetferbaum, Psycho- physiology 8. 600 (I971); G. Schechter and M. Buchsbaum, ibid. 10, 392 (1973); R. Lavine, M. S. Buchsbaum, M. Poncy, ibid. 13. 140(1976); J. Silverman, Br. J. Psychiatry 114. 1201 (1968); M. Singer, G. Borge, R. Almond. M. Buchs- baum, J. Silverman, L. C. Wynne. Clin. Res. 17, 133 (1969); M. Buchsbaum. Science 172, 502 (I971); _. F. Goodwin, D. Murphy, G. Borge, Am. J. Psychiatry 128, 51 (I971); D. A. Soskis and C. Shagass, Psychophysiology 11, 175 (I974). 3. M. Zuckennan, T. Murtaugh, J. Siegel, Psycho— physiology 11, 535 (1974). 4. R. A. Hall, M. Rappaport, H. K. Hopkins, R. Griffin, J. Silvennan, Science 170, 998 (1970). 5. F. Bremer and N. Stoupel, Acta Neurol. Psychi- atr. Belg. 58, 401 (1958); S. Dumont and P. Dell. Elsaroencephalogr. Clin. Neurophysiol. 12. 769 (1 ). 6. M. Steriade, Int. Rev. Neurobiol. 12. 87(1970). 7. Stimuli were presented three times at 20-second intervals in the following order: (i) lOO-db (A scale) noise bursts; (ii) intense light flashes (370 footcandles); (iii) high-pressure oxygen was emitted from a hose causing it to hiss and flail about; (iv) low-pressure oxygen was emitted producing a mild hiss; and (v) a mechanical. bat- tery-operated ape approached the animal swing- ing its arms and producing a loud, mechanical norse. 8. The results and behavioral descriptions from the study of Hall et al. (4) suggest that these behav- iors in cats are related to the augmenting-reduc- ing phenomenon. 9. The use of Flaxedil presents two interrelated problems: the animal when conscious can per- ceive pain, and Flaxedil when used in high dos- ages for a prolonged time can produce a com- atose state [R. Hodes, Electroencephalogr. Clin. Neurophysiol. 14, 220 (1962)]. Therefore, Flaxe- dil was continuously infused (intravenously) at the lowest rate and concentration necessary to produce paralysis and was discontinued when- ever the animal failed to desynchronize to natu- ral stimuli. Periodically all wounds were treated with local anesthetics, the eyes and tongue were moistened, and the animal was rotated and its legs flexed. The EEG, electrocardiogram, ex- pired C0,, and body temperature were contin- Iliously monitored and maintained within normal rmrts. IO. Concentric stimulation electrodes were formed from an insulated wire extending 0.5 mm from within a 24-gauge tube. The final 0.25 mm of the tip and 0.5 mm of the barrel were stripped of their insulation. Reticular coordinates were an- terior 2.0, lateral 2.5, and horizontal —1 to —2.5. This region was shown to be most efi'ective for producing long-lasting EEG desynchronization [M. Bonvallet and A. Newman-Taylor, Electro- encephalogr. Clin. Neurophysiol. 22. 54 (1967)]. 11. Reticular stimulation consisted of 0.5-second trains of 0.1-msec pulses delivered at a rate of 150 pulses per second. Each train terminated 25 msec prior to presentation of the Visual stimu- lus, wrth 30 trams given at each intensity. Three averages each consisting of five EP’s for both OT and OR stimulation were collected during each intensity of MRF stimulation. In addition, the five potentials recorded immediately pre- ceding each MRF stimulation run were aver- aged and served as baseline data. 12. J. Siege], Physiol. Behav. 3, 203 (1968). 13. One footcandle is equivalent to 10.76 lumen/m“. 14. A three-factor analysis of variance for unequal number of subjects per group indicated that the main effects for groups (augmenter-reducer) and ITI were not significant. Suprathreshold MRF stimulation significantly increased thalamic re- sponsiveness for both groups, F (5, 60) = 21.75, P < .00l. 15. T. Ogawa, Science 139, 343 (1963); D. Satinsky. Electroencephalogr. Clin. Neurophsiol. 25, 543 (1968); W. G. Tatton and D. R. Crapper. Brain Res. 47, 371 (1972); W. E. Foote, et al. Exp. Brain Res. 19, 124 (I974). 16. N. Dagino, E. Favale, C. Loeb, M. Manfredi,.l. Neurophysiol. 28, 443 (1965); J. T. Walsh and J. P. Cordeau, Exp. Neurol. 11, 80 (1965); F. Bal- dissera, M. G. Cesa-Bianchi. M. Mancia, Arch. Ital. Biol. 104. 247 (1966). 17. The groups difi'ered significantly, F(l, IO) = 5.34, P < .05, as did the groups by RF stimulation in- teraction, F (5, 50) = 3.05. P < .05. 18. M. Demetrescu, M. Demetrescu. G. Iosif, Elec- 7 OCTOBER 1977 troencephalogr. Clin. Neurophysiol. 18, 1 (1965); S. Watanabe. M. Konishi, O. D. Creutzfeldt, Exp. Brain Res. 1, 272 (1966); V. G. Skrebitsky. Brain Res. 14. 510 (1969); D. M. Feeney and J. M. Orem, Exp. Neurol. 33, 310 (1971). 19. M. Steriade. Brain Res. 9, 169 (I968). 20. J. M. Fuster. Science 133, 2011 (I961); J. Orem and D. M. Feeney,Brain Res. 30, 200 (I971); D. M. Feeney and J. M. Orem. Physiol. Behav. 9, 805 (1972). 21. F. E. Grubbs, paper presented at Army Science Conference. June 1966. 22. Previous results indicated a negative correlation between 151’ augmenting and withdrawal (4). We defined withdrawal as the degree of movement away from the noxious stimuli. Augmenters re- acted more to the stimuli than did the reducers and part of their initial reaction was a definite withdrawal. We have the impression that the re- ducers withdrew more to the back of their home cages when approached than did the augment- ers. The discrepancy, therefore, may be in the definition of withdrawal. 23. Supported by NSF grant BNS76-01652 to J.S. and predoctoral support from US. Army Hu- man Engineering Laboratory to J.H.L. 31 January I977; revised 23 May 1977 Imitation of Facial and Manual Gestures by Human Neonates Abstract. Infants between 12 and 21 days of age can imitate both facial and manu- al gestures; this behavior cannot be explained in terms of either conditioning or innate releasing mechanisms. Such imitation implies that human neonates can equate their own unseen behaviors with gestures they see others perform. Piaget and other students of devel- opmental psychology consider the imita- tion of facial gestures to be a landmark achievement in infant development. In- fants are thought to pass this milestone at approximately 8 to 12 months of age. Infants younger than this have been pos- tulated to lack the perceptual-cognitive sophistication necessary to match a ges- ture they see with a gesture of their own which they cannot see (I). The experi- ments we report show that the infant’s imitative competence has been under- estimated. We find that 12- to 2I-day-old infants can imitate both facial and manu- al gestures (Fig. I). This result has impli- cations for our conception of innate hu- man abilities and for theories of social and cognitive development. An experimental evaluation of the ne- onate’s imitative competence raises sev- eral methodological difl‘iculties. One con- sists of distinguishing true imitation from a global arousal response. For example, one can conclude nothing about imita- tion if an infant produces more tongue protrusions in response to a tongue pro- trusion" demonstration than he does to C Fig. 1. Sample photographs from videotape recordings of 2- to 3-week-old infants imitating (a) tongue protrusion, (b) mouth opening, and (c) lip protrusion demonstrated by an adult experi- menter. 75 the presentation of a neutral facial ex- pression. It would be more parsimonious simply to conclude that a moving, human face is arousing for the infant and that in— creased oral activity is part of the in- fant’s arousal response. A second issue involves controlling interactions be— tween adult and infant that might shape the imitative response. We found that if parents were informed of the imitative tasks we planned to examine, they prac- ticed these gestures with their infants be- fore coming into the laboratory so that their baby “would do well on the test.” In reviewing films of preliminary work, we also noticed that the examiner tended to alter the rhythm of his tongue protru- sion as a function of the response of the infant. These kinds of interactions would expose findings of imitation to a variety of explanations, including the possibility that the infants were merely being condi- tioned to imitate tongue protrusion. A third issue concerns the scoring of the in- fant’s responses. The movements tested were not generally produced in a dis- crete, unambiguous fashion, and not sur- prisingly, there were gross differences in the scoring as a function of whether or not 33— 301 271 26- 24* Total number of “YES" judgments 5 L_._1 LP MO TP SFM LP MO TP SFM the observer knew which gesture had been demonstrated to the infant. In the experiments we now report, these three issues are addressed as fol- lows. (i) Each infant’s response to one gesture is compared to his response to another similar gesture demonstrated by the same adult, at the same distance from the infant, and at the same rate of movement. For instance, we test wheth- er infants produce more tongue protru— sions after an adult demonstrates tongue protrusion than after the same adult demonstrates mouth opening, and vice versa. If differential imitation occurs, it cannot be attributed to a mere arousal of oral activity by a dynamic, human face. (ii) Parents were not told that we were examining imitation until after the stud- ies were completed; moreover, the ex— periments were designed to preclude the possibility that the experimenter might alter the rhythm of his demonstration as a function of the infant’s response. (iii) The infant’s reactions were videotaped and then scored by observers who were uninformed of the gesture shown to the infant they were scoring (2). In experiment 1, the subjects were six §\\ LP MO TP SFM LP M0 TP SFM Gesture shown to infant Fig. 2. Distribution of “yes” judgments as a function of the gesture shown to the infant during experiment I. The maximum possible number ofjudgments for each bar was 36 (six infants and six judges). Shaded bars indicate the imitative reaction. (a) Number ofjudgments that infants responded with lip protrusion (LP) to each of the four gestures shown them, (b) mouth—opening (M0) judgments, (c) tongue-protrusion (TP) judgments, and (d) sequential-finger—movement (SFM) judgments. Condition Experimenter Baseline Baseline period Experimental Response period 1 Experimental Response period 2 exposure (150 seconds) exposure 1 (150 seconds) exposure 2 (150 seconds) ace infants ranging in age from 12 to 17 days ()7 = 14.3 days). Three were male and three female. Testing began with a 90- second period in which the experimenter presented an unreactive, “passive face” (lips lclosed, neutral facial expression) to the infant. Each infant was then shown the following four gestures in a different random order: lip protrusion, mouth opening, tongue protrusion, and sequen- tial finger movement (opening and clos- ing the hand by serially moving the fin- gers). Each gesture was demonstrated four times in a lS-second stimulus-pre- sentation period. This period was imme- diately followed by a 20-second response period for which the experimenter stopped performing the gesture and re- sumed a passive face. In order to allow for the possibility that the infants might not watch the first stimulus presentation, the procedure allowed a maximum of three stimulus presentations and corre- sponding response periods for any one gesture. Half the cases required only one stimulus presentation. In those cases ne- cessitating more than one stimulus pre- sentation, the 20-second response period used in assessing imitation was the one following the final presentation of the gesture. A 70-second passive-face period separated the presentation of each new type of gesture from preceding ones. The videotape recordings of the re- sponse periods were scored in a random order by undergraduate volunteers. Two groups of six coders were used. One group scored the infant’s facial behavior; the other scored the manual responses. The face coders were informed that the infant in each videotaped segment was shown one of the following four ges- tures: lip protrusion, mouth opening, tongue protrusion, or passive face. They were instructed to order the four ges- tures by ranks from the one they thought it most likely the infant in each segment was imitating to the one they thought was least likely. No other training was given. The hand coders were treated identically, except that they were in- formed that the infant in each segment was presented with one of the following Fig. 3. Schematic illustration of the pacifier technique for assessing facial imitation in neonates in experiment 2. Half of the infants were exposed to the gestures in the order tongue protrusion, mouth opening; the other half were exposed to the gestures in the reverse order. 76 SCIENCE, VOL. 198 hand gestures: sequential finger move- ment, finger protrusion, hand opening, or passive hand. For the purposes of analysis, the two highest ranks and the two lowest ranks were collapsed. This procedure yields di- chotomous judgments of whether it was likely or unlikely (hereafter referred to as “yes” or “‘no”) that the infants were im- itating a particular gesture. The distribu- tion of “yes” judgments for each infant gesture peaked when the corresponding gesture was demonstrated by the experi- menter (Fig. 2). In all four instances, Cochran Q tests (3) reveal that the judged behavior of the infants varies sig- nificantly as a function of the gestures they are shown [lip protrusion, P < .01 (Fig. 2a); mouth opening, P < .02 (Fig. 2b); tongue protrusion, P < .05 (Fig. 2c); and sequential finger movement, P < .001 (Fig. 2d)]. That this variation is attributable to imitation is supported by the fact that none of these effects is sig- nificant when the judgments correspond- ing to the imitative reaction (shaded col- umns in Fig. 2) are excluded from the analyses. Experiment I avoided a prolonged stimulus-presentation period during which the experimenter might alter the timing of his gesturing as a function of the infant’s responses. However, in adopting a fixed stimulus-presentation period as brief as 15 seconds, it was sometimes necessary to repeat the pre- sentation to ensure that the infants ac- tually saw the gesture they were to imi- tate. This procedure then opened the possibility that the experimenter might unwittingly have been prefiltering the data by readministering the stimulus pre- sentations until the random behavior of the infant coincided with the behavior demonstrated. A second study was therefore designed which is not open to this potential objection. The subjects in experiment 2 were 12 infants ranging in age from 16 to 21 days (2? = 19.3). Six were male and six fe- male. They were shown both a mouth- opening and a tongue-protrusion gesture in a repeated-measures design, counter- balanced for order of presentation. The experimental procedure is illustrated in Fig. 3. Testing began with the insertion of a pacifier into the infant’s mouth. In- fants were allowed to suck on it for 30 seconds while the experimenter present- ed a passive face. The pacifier was then removed, and a 150-second baseline pe- riod was timed. After the baseline peri- od, the pacifier was reinserted into the infant’s mouth, and the first gesture was demonstrated until the experimenter 7 OCTOBER 1977 m o 10 a b > «E» 40 8 OJ :3 g 30 6 e s. 3 E 20 4 O O. 3 10 2 D: o . . o a TF MO 8 TP MO ongue protrusions Mouth openings Experimental condition Fig. 4. Total frequency of (a) tongue-protru- sion and (b) mouth-opening responses for three conditions in experiment 2. Abbrevi- ations: B, baseline period; TP, tongue-protru- sion response period; and M0, mouth-open- ing response period. judged that the infant had watched it for 15 seconds. The experimenter then stopped gesturing, resumed a passive face, and only then removed the pacifier. A ISO-second response period, during which the experimenter maintained his passive face, was clocked. Immediately thereafter the pacificer was reinserted, and the second gesture was presented in an identical manner (4). Infants did not tend to open their mouths and let the pacifier drop “out dur- ing the mouth-opening demonstration; nor did they push out the pacifier with their tongues during the tongue-protru- sion demonstration. On the contrary, they sucked actively with the pacifier re- maining firmly within their mouths dur- ing the stimulus-presentation period. Thus, the pacifier technique (i) safe- guards against the experimenter’s alter- ing his gesturing as a function of the imi- tative responses Of the infant and (ii) per- mits the experimenter to demonstrate the gesture until the infant has seen it, while ensuring that the experimenter’s assessment of this point is uncon- taminated by any knowledge of the in- fant’s imitative response. The 36 videotaped segments (12 in- fants for 3 periods each) were scored in a random order by an undergraduate assis- tant who was uninformed of the struc- ture of the experiment. The frequencies of tongue protrusions and mouth open- ings were tallied for each videotaped seg- ment (5). The results demonstrate that neonates imitate both tongue protrusion and mouth opening (Fig. 4). As assessed by Wilcoxon matched-pairs signed-ranks tests (3), significantly more tongue-pro- trusion responses occurred after that gesture had been presented than during the baseline period (P < .005) or after the mouth-opening gesture (P < .005). Similarly, there were significantly more mouth-opening responses after that ges- ture had been demonstrated than during the baseline period (P < .05) or after the tongue-protrusion gesture (P < .05). It is noteworthy that under the present exper- imental conditions, the infants had to delay their imitation until after the ges- ture to be imitated had vanished from the perceptual field. At least three different mechanisms could potentially underlie the imitation we report. 1) It could be argued that the imitation is based on reinforcement administered by either the experimenter or the par- ents. In order to prevent the experiment- er from shaping the infant’s imitative re- sponding, the procedure directed that he maintain an unreactive, neutral face dur- ing the response period. The experiment- er’s face was videotaped throughout both experiments in order to evaluate whether this procedure was followed. The videotaped segments were shown to observers whose task it was to score any reinforcements that the experimenter ad- ministered. No smiles or vocalizations were noted in any trial. Indeed, the only changes from the passive face occurred in three trials in experiment 1, when the experimenter was judged to “blink ex- tremely rapidly.” Considering only ex- periment 2, then, the experimental pro- cedure does not appear to have been vio- lated, and therefore, differential shaping of the mouth-opening and tongue-protru- sion responses during the successive ISO-second response periods is an un- likely source of the effects obtained. Since none of the parents were informed about the nature of the study, special practice on imitative tasks at home in preparation for the experiment was avoided. Further, informal questioning revealed that no parent was aware of ever having seen babies imitating in the first 21 days of life; indeed, most were astonished at the idea. Thus, a history of parental reinforcement seems an improb- able basis for imitation at this very early age. 2) This early imitation might be based on an innate releasing mechanism such as that described by Lorenz and Tin- bergen. (6). This view would hold that tongue protrusion, mouth opening, lip protrusion, and sequential finger move- ment are each fixed—action patterns and that each is released by the correspond- ing adult gesture (sign stimulus). The overall organization of the infant’s imi— tative response, particularly its lack of stereotypy, does not favor this inter- pretation. In addition, the fact that in...
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