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The suppression of crying in the human neonate: Response to human vocal tract stimuli
BRAIN
AND
LANGUAGE
23, 34-42 (1984)
The Suppression of Crying in the Human Neonate: Response to Human Vocal Tract Stimuli SAMUELC. RICCILLO Department of Communication, University of Wyoming, Laramie AND
THOMASWATTERSON Department of Speech Pathology and Audiology, University of Wyoming, Laramie Amounts of crying were measured for two groups of infants in two states, calm and crying. The stimulus group was exposed to two test-cry stimuli (owncry/other-cry) in both states. The control group was not exposed to the test-cry stimuli. For the stimulus group, results showed that there was no significant difference in the amount of crying during presentation of either the own-cry or other-cry test stimulus. However, the stimulus group did cry significantly less than the control group. This difference in the amount of crying was attributed to the capacity of the infant to suppress crying in the presence of auditory stimuli.
INTRODUCTION Crying is among the first overt activities exhibited by a human infant at birth. This uniquely human behavior (Illingsworth, 1980; 1955) signals the onset of respiration and the completion of labor. But other functions of crying and their relationship to other vocal development remain uncertain. Crying is commonly regarded as a reflexive vocalization that represents or intentionally communicates the infant’s internal state. Adler (1946), for example, considers crying a unitary vocalization that universally signals distress and inferiority. Others have suggested that there are The authors of this paper thank the physicians, nurses, and staff at the Ivinson Memorial Hospital, Laramie, WY, for their assistance in this study. In particular, we would like to extend our special thanks to the nursery statI and obstetrical staff, without whose cooperation this study would not have been possible. Send requests for reprints to S. Riccillo, Department of Communication, University of Wyoming, Laramie, WY 82071. 34 0093-934X/84 $3.OO Copyright All rights
Q 1984 by Academic Ress, of reproduction in any form
Inc. reserved.
SUPPRESSION
OF CRYING
35
different types of cries associated with different types of internal states; for example, pain, hunger, and pleasure (Wasz-Hockert, Lind, Vuorenkoski, Partanen, & Valanne, 1968; Wolff, 1969; Gladding, 1978). Murai (1963), on the other hand, explains that crying is not at first a reflexive representation of internal state, but it eventually develops communicative intent as a signal of uncomfortable situations. In contrast, Bloom and Lahey (1978) contend that cries do not represent the internal state, but rather they are “an integral part” of the state and do not convey any communicative intent. Crying has also been explained as a reflexive response to acoustic stimuli, especially stimuli generated by a human vocal tract. That possibility is important because it implies that crying may be the first vocal response to a human voice, and therefore, the first stage of speech and language development (Lewis, 1951; Lieberman, Harris, Wolff, & Russell, 1971). Morley (1967) has theorized that reflexive crying to vocal stimuli may contribute to the onset of babbling. He suggests that reflexive crying could occur as a response to the crying of another infant or as a response to an infant’s own cry, and this behavior would serve as the primitive precursor to reduplicated or circular babbling. In that regard, recent studies have investigated the question of whether or not infants respond to different acoustic stimuli by crying in greater or lesser amounts. Simner (1971) reported that calm infants exposed to an audio recording of the cry of a 5-day-old female cried significantly more than infants exposed to silence, white noise, a computer generated cry, or the cry of an older infant (51 months). Simner speculated that newborn infants are more likely to cry reflexively as the acoustic stimulus “approaches the infant’s own cry.” He maintained that the stimulus power increases as the stimulus more closely resembles the acoustic features of the infant’s own cry. However, due to a lack of response stability in his subjects, Simner questioned any relationship between reflexive crying in the newborn and later vocal development. In contrast to Simner, Martin and Clark (1982) reported that “calm infants who heard their own cry did very little crying” and “crying infants stopped crying when they heard their own cry.” They also reported that crying infants exposed to the tape-recorded cry of another infant continued crying. These investigators interpreted their findings as evidence that reflexive crying is a selective response available to newborn infants that reflects a capacity to discriminate own cry from that of other infant cries. They suggested that this selective response is a peer- and species-specific behavior, but they did not comment on the possible relationship of this behavior to later vocal development. It occurred to us that if crying may be considered a selective response to an auditory stimulus, then the absence of crying must be an alternative response that is likewise worthy of investigation. Previous studies have
36
RICCILLO AND WATTERSON
focused attention on the number of infants who cried during stimulus presentation, but individual subjects were not exposed to more than one experimental condition. In light of Simner’s comment that reflexive crying in response to acoustic stimuli may not be a stable or consistent response, it is possible that the conflicting findings across studies are due in part to intersubject and intrasubject response variability. The present study was designed, therefore, to focus attention on the amount of crying that occurred during the presentation of both own and other test-cry stimuli. To minimize the potential intersubject and intrasubject response variability, each subject was included under each experimental condition. This would allow each subject to act as his or her own control. The experimental subjects were also compared to a control group who were not exposed to the test cry stimuli. METHOD Subjects Fifty-eight infants born at Ivinson Memorial Hospital, Lararnie, Wyoming, served as the subjects for this study. Twenty-seven of the subjects were females, and thirty-one were males. All of the subjects were born between 1 September 1982 and 26 November 1982. APGAR scores and estimates of gestational age were determined for each subject by attending physicians and obstetrical nurses. Each subject selected was medically normal and the result of full-term pregnancy. At the time of birth, each of the 58 subjects was randomly assigned to either a “stimulus” group or to a “control” group. The stimulus group was composed of 16 males and 13 females (N = 29) and the control group was composed of 14 males and 15 females (N = 29).
Stimuli To provide the data of interest in this study, 30 test-cry listening tapes were constructed. Twenty-nine listening tapes contained the individual cry of each of the 29 subjects in the stimulus group (own-cry), and one listening tape containing the cry of another infant (other-
cry). To obtain the own-cry test stimuli, each subject was brought to a quiet admitting area of the nursery shortly after birth. Each subject was then observed for a maximum of 20 min. During this observation, all crying was magnetically recorded using a Pioneer audiorecorder (Model RT 701) and amplifier (Model 5A-6500) with a Realistic dynamic microphone. The mouth-to-microphone distance was approximately 15 cm. All cry samples were unprovoked and they were obtained before the subject was exposed to any crying by other infants. Each original recording was then reviewed and a representative segment of the cry was selected for repeated dubbing. Each representative segment was at least 10 set in duration and each was preceded and followed by silence on the original recording. The selected segment was then dubbed repeatedly with a matched audiorecorder (Pioneer, Model RT 701) to make a 4-min listening tape. The 4-min listening tape of each infant’s cry became the own-cry test stimulus, respectively, for each of the 29 subjects in the stimulus group. The other-cry test stimulus was obtained by the same procedure as each own-cry test stimulus. The subject who provided the other-cry stimulus was a full-term, clinically normal female infant. The representative segment of her cry was 12 set in duration. This segment was dubbed repeatedly to make the 4-min listening tape that was eventually presented to each subject in the stimulus group.
SUPPRESSION OF CRYING
37
During test-cry stimulus presentation, these listening tapes were replayed at approximately equal intensity. To accomplish that, a sound level meter (Bruel-Kjaer, Type 2203) was placed in an empty crib so that the microphone would be at the approximate location of a subject’s head. Then, the audio speaker was positioned so that it was 20 cm above and 16 cm behind the sound level meter microphone. After each listening tape was made, it was played to the sound level meter and the reproduce intensity was adjusted so that the stimulus was approximately 80 dB SPL (re: 20 PPa). This intensity was chosen because it is similar to that of an infant’s own cry and should not produce a startle effect (Ringel & Kluppel, 1964; Ostwald, 1963). The position of the reproduce intensity control was then noted so that it could be adjusted appropriately for presentation of the test-cry stimulus at a later time. Only minor intensity adjustments were necessary across stimuli.
Procedure Each subject was observed in the nursery to determine if he/she was in a calm state or in a crying state. A calm state was defined as a condition where both eyes were open and there was an absence of facial grimaces and crying (or other vocalizations). A crying state was defined as a condition where both eyes were closed, with facial grimacing and openmouth vocalization commonly recognized as crying. Subjects were not considered to be in a crying state if either examiner perceived any external stimulus that might promote or maintain crying. When both examiners agreed that a subject was in a desired state for a period of at least one minute, the subject’s mobile crib was pushed to a quiet “testing” room near the nursery. Timing of the desired state was done with a digital stopwatch, operated by one examiner. Transportation to the testing room took approximately 15 sec. If the subject’s state changed during transportation, or at any time prior to stimulus presentation, the subject was returned to the nursery for continued observation. Once in the testing room, the subject’s crib was positioned so that the audio speaker was 20 cm above and 16 cm behind the subject’s head. Then, an appropriate test-cry listening tape was presented. As the 4-min test-cry stimulus was played, the amount of crying was measured in seconds on an event recorder (Esterline Angus, Model A) controlled by one of the examiners. Stimulus duration was checked during presentation by having one examiner time the signal with a stopwatch and the other examiner time with the constant speed event recorder. When a subject cried, a control button was depressed on the event recorder causing a pen to deflect from baseline. When the infant ceased crying, the button was released and the deflected pen returned to baseline. This produced a permanent graphic record of the onset, duration, and offset of each cry episode. Eventually, each of two test-cry listening tapes (own-cry, other-cry) was presented to each subject in the stimulus group during a calm state and during a crying state. Thus, each subject was tested on four separate occasions. The subjects’ mean age at the completion of four testing occasions was 38 hr. The control group was treated like the stimulus group, except that test-cry stimuli were not presented. Thus, each control subject was transported to the test room both in a calm state and in a crying state, and the amount of crying that occurred in each state was measured in seconds on the event recorder. The mean age of the control group at the completion of the two testing occasions was 35 hr.
Measurement
Reliability
A remote switch was attached to a second recording pen on the event recorder so that it could be operated by the other examiner. Then, the amount of crying was measured independently by each examiner for 15 randomly selected subjects. Seven of the subjects were in a calm state and eight were in a crying state. Interjudge reliability was evaluated by obtaining a Pearson r correlation coefficient that indicated the degree of relationship
38
RICCILLO AND WATTERSON
between the amount of crying recorded by each examiner during the fifteen 4-min tests. The obtained correlation coefficient was .99. Thus, it was concluded that the data obtained in this study were statistically reliable.
RESULTS Two test-cry stimuli were presented to each of the 29 subjects in the stimulus group during a calm state and during a crying state. Table 1 presents the mean amounts of crying for the stimulus group by type of stimulus (own-cry, other-cry), state of subject (calm, crying), and sex. The findings were tested for significance with a 2 x 2 x 2 (type of stimulus x state of subject X sex) analysis of variance with repeated measures (Winer, 1971). That analysis revealed no significant main effect for sex of subject, F(1, 27) = 0.79. The analysis also showed that there was no significant difference in the amount of crying during presentation of either the own-cry or the other-cry test stimulus, F(1, 27) = 0.03. This effect was obtained both for the calm state and for the crying state. In a calm state, the subjects cried an average of 17.69set during presentation of the own-cry test stimulus, and an average of 13.26set during presentation of the other-cry test stimulus. In a crying state, the subjects cried an average of 88.80 set during presentation of the own-cry, and an average of 96.52 set during presentation of the other-cry. Thus, the subjects in this study did not respond differently to the two test-cry stimuli by crying in greater or lesser amounts. As might be expected, the analysis did show that when the subjects were in a crying state, they cried significantly more than when they were TABLE 1 MEAN
DURATIONS
OF CRYING
IN SEC FOR THE STIMULUS TEST-CRY STIMULUS
GROUP BY SEX, STATE, AND
Own cry Means (SD) Calm
Males (16) Females (13) Total (29)
Crying
Males (16) Females (13) Total (29)
19.88 (40.13) 15.00 (26.29) 17.69 (34.13) 92.02 (54.21) 84.83 (52.90) 88.80 (52.80)
Other cry
No. Crying 7 7 14 16 13 29
Means (SD) 14.10 (29.67) 12.23 (29.98) 13.26 (29.26) 103.20 (65.79) 88.29 (64.99) 96.52 (64.70)
No. Crying 5 4 9 16 13 29
SUPPRESSION
39
OF CRYING
in a calm state, F(1, 27) = 64.47; p < .OOO.The overall mean amount of crying when the subjects were in a calm state was 15.48 set, and the overall mean amount of crying in a crying state was 92.66 sec. Finally, there was no statistically significant interaction among the main variables analyzed in this design. Thus, the reported results did not vary in an unpatterned way. It was also of interest in the present study to compare the stimulus group with a control group. The control group was treated like the stimulus group in that the mean amount of crying was measured for 4 min during a calm state and during a crying state, but test-cry stimuli were not presented to the control subjects. Table 2 presents the mean amounts of crying for the control group and for presentation of the own-cry to the stimulus group. A 2 x 2 (own-cry/control x state of subject) analysis of variance with repeated measures showed a significant difference between the own-cry test stimulus and the control group, F(1, 54) = 14.96; p < .0003, and a significant difference for state of subject, F(1, 54) = 87.22; p < .OOO.As Table 2 shows, the stimulus group cried significantly less than the control group during presentation of the own-cry test stimulus both in a calm state and in a crying state. Also, subjects in a calm state cried significantly less than subjects in a crying state regardless of the stimulus. There was no significant interaction among the main variables. Table 3 presents the mean amounts of crying for the control group and for presentation of the other-cry to the stimulus group. Again, a 2 x 2 (other-cry/control x state of subject) analysis of variance with repeated measures revealed a significant difference between the othercry test stimulus and the control group F(1, 54) = 9.08; p < .0039, and a significant difference for state of subject, F(1, 54) = 100.41; p < .OOO. As shown in Table 3, the stimulus group cried significantly less than the control group during presentation of the other-cry test stimulus, both in a calm state and in a crying state. Calm subjects cried significantly less than crying subjects regardless of stimulus and there was no significant TABLE 2 MEAN DURATIONS OF CRYING IN SEC FOR THE CONTROL GROUP AND FOR PRESENTATIONOF OWN-CRY TO THE STIMULUS GROUP BY STATE Own-cry Means (SD) Calm Crying
17.69 (34.13) 88.80 (52.80)
stimulus
Control
No. Crying 14 29
Means (SD) 20.65 (39.99) 137.77 (51.83)
No. Crying 9 29
40
RICCILLO AND WATTERSON TABLE 3
MEAN DURATIONS OF CRYING IN SEC FOR THE CONTROL GROUP AND FOR PRESENTATIONOF OTHER-CRY TO THE STIMULUS GROUP BY STATE
Other-cry stimulus Means (SD) Calm Crying
13.26 (29.96) 96.52 (64.70)
Control
No. Crying 9 29
Means (SD) 20.65 (39.99) 137.71 (51.83)
No. Crying 9 29
interaction among the main variables. Thus, presentation of either test cry stimulus appeared to suppress the crying output of the stimulus group even though they did not respond differently to the two test-cry stimuli. DISCUSSION The present study focused on whether or not newborn infants would respond differently to their own cry than to the cry of another newborn infant. The obtained results indicated that the subjects in this study did not differentiate these similar stimuli by crying in greater or lesser amounts. Whether in a calm state, or in a crying state, there was no significant difference in the amount of crying during presentation of either the owncry or the other-cry test stimulus. In that regard, the results stand in contrast to findings reported in previous investigations (Simner, 1971; Martin & Clark, 1982). The differences in findings across studies could be explained, however, by the different experimental methods employed by the different investigators. In the present study, the lack of crying was regarded as a response alternative to overt crying while previous studies have disregarded the lack of crying as a possible response. Like previous investigators, we also noticed that some infants are more likely to cry than others during stimulus presentation, but we found no evidence that their amount of crying could be explained as a discriminative response to our stimuli. Although the subjects in the present study did not appear to discriminate their own cry from the cry of another infant, it did appear that the presentation of the test-cry stimuli influenced their overall cry behavior. When the stimulus group was compared to the control group, statistical analysis showed that the stimulus group cried significantly less than the control group during presentation of either test-cry stimulus for both the calm state and for the crying state. Possibly this reduction in crying during the stimulus presentation reflects suppression of a crying reflex. It is well known that a newborn human infant is dominated by a variety of primitive reflexes that serve primitive needs (Langer, 1969; Gesell,
SUPPRESSION OF CRYING
41
1945; Wolff, 1969; Watson, 1962; Piaget, 1971; Whitaker, 1976). As part of the process of maturation, these primitive reflexes must be suppressed, modified, and/or shaped into volitional behavior (Mysak, 1968; Hardy, 1983). For example, the rooting and sucking reflexes provide the newborn infant with the physiologic basis to obtain liquid nourishment. However, these same reflexes must be suppressed and modified to permit progression to solid food, Crying may be one of the primitive reflexes present at birth, and, like other primitive reflexes, it serves primitive needs. Those needs might include signaling caretakers or obtaining respiratory exercise or a variety of other needs. But, in the course of maturation, the infant must suppress crying because it would interfere with auditory-vocal development and the subsequent progression to more efficient methods of communication. Evidence that crying is a suppressed primitive reflex may be gleaned from the literature on brain-injured adults. Neural lesions in adults may release lower neural centers from the necessary influence of inhibitory mechanisms. This release of inhibition may result in the recurrence of primitive reflexes such as sucking (Truex & Carpenter, 1969; Darley, Aronson, & Brown, 1975; Hardy, 1983). Spontaneous crying is a common symptom of bilateral pyramidal tract lesion (pseudobulbar palsy) (Darley et al., 1975). It seems possible, then, that such symptomatic crying may represent a release of inhibition to a reflexive mechanism that is normally suppressed. Certainly it is difhcult for any individual to receive and perceive auditory stimuli while in the act of generating competing noise. Humans perceive auditory stimuli and humans generate auditory stimuli, but they do not effectively engage in both simultaneously. It may be that the human infant suppresses the crying reflex in the presence of auditory stimuli in order to listen. If that is the case, suppression of the crying reflex may represent the infant’s first “attempt” to interact with its auditory environment. As the primitive nervous system gradually matures, reflexive crying would proportionately decrease in frequency. This decrease in cry occurrences would then permit noncry vocalizations to develop in context-free situations, and these vocalizations would have the potential to develop symbolic meaning (Murai, 1963). Thus, cry suppression may be the neuro-social mechanism that functions as the link between crying and other vocalizations. Possibly, the luck of crying is more important to the development of vocalization than the act of crying itself. REFERENCES Adler, A. 1946. The psychology of early childhood. London: Methuen. Bloom, L., & Lahey, M. 1978. Language development and language disorders. New York: Wiley. Darley, F., Aronson, A., & Brown, J. 1975.Motor speech disorders. Philadelphia: Saunders. Gesell, A. 1945. The embryology of behavior. New York: Harper.
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Gladding, S. T. 1978. Empathy, gender, and training as factors in the identification of normal infant cry signals. Perceptual and Motor Skills, 47, 267-270. Hardy, J. 1983. Cerebral palsy. Englewood Cliffs, NJ: Prentice-Hall. Illingsworth, R. S. 1955. Crying in infants and children. British Medical Journal, 1, 75. Illingsworth, R. S. 1980. The development of communication in the first year and the factors which affect it. In T. Murry & J. Murry (Eds.), Infant communication: Cry and enrly speech. Houston: College-Hill Press. Langer, J. 1969. Theories of development. New York: Holt, Rinehart & Winston. Lewis, M. M. 1951. Infant speech. New York: Humanities Press. Lieberman, P., Harris, K. S., Wolff, P., & Russell, L. H. 1971. Newborn infant cry and nonhuman primate vocalizations. Journal of Speech and Hearing Research, 14, 718727. Martin, G. B., & Clark III, R. D. 1982. Distress crying in neonates. Developmental Psychology,
18, 3-9.
Morley, M. E. 1967. The development and disorders of speech in childhood. Baltimore: Williams & Wilkins. Murai, J. 1963. The sounds of infants: Their phonemicazation and symbolization. Studia Phonologica, 3, 17-34. Mysak, E. D. 1968. Neuroevolutional approach to cerebral palsy and speech. New York: Teachers College Press. Ostwald, P. 1953. Soundmaking: The acoustical communication of emotion. Springfield, IL: Thomas. Piaget, J. 1971. Biology and knowledge. Chicago: Univ. of Chicago Press. Ringel, R. L., KzKluppel, D. D. 1964.Neonatal crying: A normative study. Folia Phoniatrica, 16, 1-9. Simner, M. L. 1971. Newborn’s response to the cry of another infant. Developmental Psychology, 5, 136-150. Truex, R., & Carpenter, M. 1969. Human neuroanatomy. Baltimore: Williams and Wilkins. Wasz-Hockert, O., Lind, J., Vuorenkoski, V., Partanen, T., & Valanne, E. 1968. The infant cry, a spectrographic and auditory analysis. Clinics in developmental medicine, 29, l-42. Watson, J. B. 1962. Behaviorism. Chicago: Univ. of Chicago Press. Whitaker, H. 1976. Neurobiology of language. In E. C. Carterette & M. P. Friedman (Eds.), Handbook of perception. New York: Academic Press. Winer, B. 1971. Statistical principles in experimental design. New York: McGraw-Hill. Wolff, P. H. 1969.Crying and vocalization in early infancy. In B. M. Foss (Ed.), Determinants of infant behavior. New York: Wiley. Vol. IV.
AND
LANGUAGE
23, 34-42 (1984)
The Suppression of Crying in the Human Neonate: Response to Human Vocal Tract Stimuli SAMUELC. RICCILLO Department of Communication, University of Wyoming, Laramie AND
THOMASWATTERSON Department of Speech Pathology and Audiology, University of Wyoming, Laramie Amounts of crying were measured for two groups of infants in two states, calm and crying. The stimulus group was exposed to two test-cry stimuli (owncry/other-cry) in both states. The control group was not exposed to the test-cry stimuli. For the stimulus group, results showed that there was no significant difference in the amount of crying during presentation of either the own-cry or other-cry test stimulus. However, the stimulus group did cry significantly less than the control group. This difference in the amount of crying was attributed to the capacity of the infant to suppress crying in the presence of auditory stimuli.
INTRODUCTION Crying is among the first overt activities exhibited by a human infant at birth. This uniquely human behavior (Illingsworth, 1980; 1955) signals the onset of respiration and the completion of labor. But other functions of crying and their relationship to other vocal development remain uncertain. Crying is commonly regarded as a reflexive vocalization that represents or intentionally communicates the infant’s internal state. Adler (1946), for example, considers crying a unitary vocalization that universally signals distress and inferiority. Others have suggested that there are The authors of this paper thank the physicians, nurses, and staff at the Ivinson Memorial Hospital, Laramie, WY, for their assistance in this study. In particular, we would like to extend our special thanks to the nursery statI and obstetrical staff, without whose cooperation this study would not have been possible. Send requests for reprints to S. Riccillo, Department of Communication, University of Wyoming, Laramie, WY 82071. 34 0093-934X/84 $3.OO Copyright All rights
Q 1984 by Academic Ress, of reproduction in any form
Inc. reserved.
SUPPRESSION
OF CRYING
35
different types of cries associated with different types of internal states; for example, pain, hunger, and pleasure (Wasz-Hockert, Lind, Vuorenkoski, Partanen, & Valanne, 1968; Wolff, 1969; Gladding, 1978). Murai (1963), on the other hand, explains that crying is not at first a reflexive representation of internal state, but it eventually develops communicative intent as a signal of uncomfortable situations. In contrast, Bloom and Lahey (1978) contend that cries do not represent the internal state, but rather they are “an integral part” of the state and do not convey any communicative intent. Crying has also been explained as a reflexive response to acoustic stimuli, especially stimuli generated by a human vocal tract. That possibility is important because it implies that crying may be the first vocal response to a human voice, and therefore, the first stage of speech and language development (Lewis, 1951; Lieberman, Harris, Wolff, & Russell, 1971). Morley (1967) has theorized that reflexive crying to vocal stimuli may contribute to the onset of babbling. He suggests that reflexive crying could occur as a response to the crying of another infant or as a response to an infant’s own cry, and this behavior would serve as the primitive precursor to reduplicated or circular babbling. In that regard, recent studies have investigated the question of whether or not infants respond to different acoustic stimuli by crying in greater or lesser amounts. Simner (1971) reported that calm infants exposed to an audio recording of the cry of a 5-day-old female cried significantly more than infants exposed to silence, white noise, a computer generated cry, or the cry of an older infant (51 months). Simner speculated that newborn infants are more likely to cry reflexively as the acoustic stimulus “approaches the infant’s own cry.” He maintained that the stimulus power increases as the stimulus more closely resembles the acoustic features of the infant’s own cry. However, due to a lack of response stability in his subjects, Simner questioned any relationship between reflexive crying in the newborn and later vocal development. In contrast to Simner, Martin and Clark (1982) reported that “calm infants who heard their own cry did very little crying” and “crying infants stopped crying when they heard their own cry.” They also reported that crying infants exposed to the tape-recorded cry of another infant continued crying. These investigators interpreted their findings as evidence that reflexive crying is a selective response available to newborn infants that reflects a capacity to discriminate own cry from that of other infant cries. They suggested that this selective response is a peer- and species-specific behavior, but they did not comment on the possible relationship of this behavior to later vocal development. It occurred to us that if crying may be considered a selective response to an auditory stimulus, then the absence of crying must be an alternative response that is likewise worthy of investigation. Previous studies have
36
RICCILLO AND WATTERSON
focused attention on the number of infants who cried during stimulus presentation, but individual subjects were not exposed to more than one experimental condition. In light of Simner’s comment that reflexive crying in response to acoustic stimuli may not be a stable or consistent response, it is possible that the conflicting findings across studies are due in part to intersubject and intrasubject response variability. The present study was designed, therefore, to focus attention on the amount of crying that occurred during the presentation of both own and other test-cry stimuli. To minimize the potential intersubject and intrasubject response variability, each subject was included under each experimental condition. This would allow each subject to act as his or her own control. The experimental subjects were also compared to a control group who were not exposed to the test cry stimuli. METHOD Subjects Fifty-eight infants born at Ivinson Memorial Hospital, Lararnie, Wyoming, served as the subjects for this study. Twenty-seven of the subjects were females, and thirty-one were males. All of the subjects were born between 1 September 1982 and 26 November 1982. APGAR scores and estimates of gestational age were determined for each subject by attending physicians and obstetrical nurses. Each subject selected was medically normal and the result of full-term pregnancy. At the time of birth, each of the 58 subjects was randomly assigned to either a “stimulus” group or to a “control” group. The stimulus group was composed of 16 males and 13 females (N = 29) and the control group was composed of 14 males and 15 females (N = 29).
Stimuli To provide the data of interest in this study, 30 test-cry listening tapes were constructed. Twenty-nine listening tapes contained the individual cry of each of the 29 subjects in the stimulus group (own-cry), and one listening tape containing the cry of another infant (other-
cry). To obtain the own-cry test stimuli, each subject was brought to a quiet admitting area of the nursery shortly after birth. Each subject was then observed for a maximum of 20 min. During this observation, all crying was magnetically recorded using a Pioneer audiorecorder (Model RT 701) and amplifier (Model 5A-6500) with a Realistic dynamic microphone. The mouth-to-microphone distance was approximately 15 cm. All cry samples were unprovoked and they were obtained before the subject was exposed to any crying by other infants. Each original recording was then reviewed and a representative segment of the cry was selected for repeated dubbing. Each representative segment was at least 10 set in duration and each was preceded and followed by silence on the original recording. The selected segment was then dubbed repeatedly with a matched audiorecorder (Pioneer, Model RT 701) to make a 4-min listening tape. The 4-min listening tape of each infant’s cry became the own-cry test stimulus, respectively, for each of the 29 subjects in the stimulus group. The other-cry test stimulus was obtained by the same procedure as each own-cry test stimulus. The subject who provided the other-cry stimulus was a full-term, clinically normal female infant. The representative segment of her cry was 12 set in duration. This segment was dubbed repeatedly to make the 4-min listening tape that was eventually presented to each subject in the stimulus group.
SUPPRESSION OF CRYING
37
During test-cry stimulus presentation, these listening tapes were replayed at approximately equal intensity. To accomplish that, a sound level meter (Bruel-Kjaer, Type 2203) was placed in an empty crib so that the microphone would be at the approximate location of a subject’s head. Then, the audio speaker was positioned so that it was 20 cm above and 16 cm behind the sound level meter microphone. After each listening tape was made, it was played to the sound level meter and the reproduce intensity was adjusted so that the stimulus was approximately 80 dB SPL (re: 20 PPa). This intensity was chosen because it is similar to that of an infant’s own cry and should not produce a startle effect (Ringel & Kluppel, 1964; Ostwald, 1963). The position of the reproduce intensity control was then noted so that it could be adjusted appropriately for presentation of the test-cry stimulus at a later time. Only minor intensity adjustments were necessary across stimuli.
Procedure Each subject was observed in the nursery to determine if he/she was in a calm state or in a crying state. A calm state was defined as a condition where both eyes were open and there was an absence of facial grimaces and crying (or other vocalizations). A crying state was defined as a condition where both eyes were closed, with facial grimacing and openmouth vocalization commonly recognized as crying. Subjects were not considered to be in a crying state if either examiner perceived any external stimulus that might promote or maintain crying. When both examiners agreed that a subject was in a desired state for a period of at least one minute, the subject’s mobile crib was pushed to a quiet “testing” room near the nursery. Timing of the desired state was done with a digital stopwatch, operated by one examiner. Transportation to the testing room took approximately 15 sec. If the subject’s state changed during transportation, or at any time prior to stimulus presentation, the subject was returned to the nursery for continued observation. Once in the testing room, the subject’s crib was positioned so that the audio speaker was 20 cm above and 16 cm behind the subject’s head. Then, an appropriate test-cry listening tape was presented. As the 4-min test-cry stimulus was played, the amount of crying was measured in seconds on an event recorder (Esterline Angus, Model A) controlled by one of the examiners. Stimulus duration was checked during presentation by having one examiner time the signal with a stopwatch and the other examiner time with the constant speed event recorder. When a subject cried, a control button was depressed on the event recorder causing a pen to deflect from baseline. When the infant ceased crying, the button was released and the deflected pen returned to baseline. This produced a permanent graphic record of the onset, duration, and offset of each cry episode. Eventually, each of two test-cry listening tapes (own-cry, other-cry) was presented to each subject in the stimulus group during a calm state and during a crying state. Thus, each subject was tested on four separate occasions. The subjects’ mean age at the completion of four testing occasions was 38 hr. The control group was treated like the stimulus group, except that test-cry stimuli were not presented. Thus, each control subject was transported to the test room both in a calm state and in a crying state, and the amount of crying that occurred in each state was measured in seconds on the event recorder. The mean age of the control group at the completion of the two testing occasions was 35 hr.
Measurement
Reliability
A remote switch was attached to a second recording pen on the event recorder so that it could be operated by the other examiner. Then, the amount of crying was measured independently by each examiner for 15 randomly selected subjects. Seven of the subjects were in a calm state and eight were in a crying state. Interjudge reliability was evaluated by obtaining a Pearson r correlation coefficient that indicated the degree of relationship
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RICCILLO AND WATTERSON
between the amount of crying recorded by each examiner during the fifteen 4-min tests. The obtained correlation coefficient was .99. Thus, it was concluded that the data obtained in this study were statistically reliable.
RESULTS Two test-cry stimuli were presented to each of the 29 subjects in the stimulus group during a calm state and during a crying state. Table 1 presents the mean amounts of crying for the stimulus group by type of stimulus (own-cry, other-cry), state of subject (calm, crying), and sex. The findings were tested for significance with a 2 x 2 x 2 (type of stimulus x state of subject X sex) analysis of variance with repeated measures (Winer, 1971). That analysis revealed no significant main effect for sex of subject, F(1, 27) = 0.79. The analysis also showed that there was no significant difference in the amount of crying during presentation of either the own-cry or the other-cry test stimulus, F(1, 27) = 0.03. This effect was obtained both for the calm state and for the crying state. In a calm state, the subjects cried an average of 17.69set during presentation of the own-cry test stimulus, and an average of 13.26set during presentation of the other-cry test stimulus. In a crying state, the subjects cried an average of 88.80 set during presentation of the own-cry, and an average of 96.52 set during presentation of the other-cry. Thus, the subjects in this study did not respond differently to the two test-cry stimuli by crying in greater or lesser amounts. As might be expected, the analysis did show that when the subjects were in a crying state, they cried significantly more than when they were TABLE 1 MEAN
DURATIONS
OF CRYING
IN SEC FOR THE STIMULUS TEST-CRY STIMULUS
GROUP BY SEX, STATE, AND
Own cry Means (SD) Calm
Males (16) Females (13) Total (29)
Crying
Males (16) Females (13) Total (29)
19.88 (40.13) 15.00 (26.29) 17.69 (34.13) 92.02 (54.21) 84.83 (52.90) 88.80 (52.80)
Other cry
No. Crying 7 7 14 16 13 29
Means (SD) 14.10 (29.67) 12.23 (29.98) 13.26 (29.26) 103.20 (65.79) 88.29 (64.99) 96.52 (64.70)
No. Crying 5 4 9 16 13 29
SUPPRESSION
39
OF CRYING
in a calm state, F(1, 27) = 64.47; p < .OOO.The overall mean amount of crying when the subjects were in a calm state was 15.48 set, and the overall mean amount of crying in a crying state was 92.66 sec. Finally, there was no statistically significant interaction among the main variables analyzed in this design. Thus, the reported results did not vary in an unpatterned way. It was also of interest in the present study to compare the stimulus group with a control group. The control group was treated like the stimulus group in that the mean amount of crying was measured for 4 min during a calm state and during a crying state, but test-cry stimuli were not presented to the control subjects. Table 2 presents the mean amounts of crying for the control group and for presentation of the own-cry to the stimulus group. A 2 x 2 (own-cry/control x state of subject) analysis of variance with repeated measures showed a significant difference between the own-cry test stimulus and the control group, F(1, 54) = 14.96; p < .0003, and a significant difference for state of subject, F(1, 54) = 87.22; p < .OOO.As Table 2 shows, the stimulus group cried significantly less than the control group during presentation of the own-cry test stimulus both in a calm state and in a crying state. Also, subjects in a calm state cried significantly less than subjects in a crying state regardless of the stimulus. There was no significant interaction among the main variables. Table 3 presents the mean amounts of crying for the control group and for presentation of the other-cry to the stimulus group. Again, a 2 x 2 (other-cry/control x state of subject) analysis of variance with repeated measures revealed a significant difference between the othercry test stimulus and the control group F(1, 54) = 9.08; p < .0039, and a significant difference for state of subject, F(1, 54) = 100.41; p < .OOO. As shown in Table 3, the stimulus group cried significantly less than the control group during presentation of the other-cry test stimulus, both in a calm state and in a crying state. Calm subjects cried significantly less than crying subjects regardless of stimulus and there was no significant TABLE 2 MEAN DURATIONS OF CRYING IN SEC FOR THE CONTROL GROUP AND FOR PRESENTATIONOF OWN-CRY TO THE STIMULUS GROUP BY STATE Own-cry Means (SD) Calm Crying
17.69 (34.13) 88.80 (52.80)
stimulus
Control
No. Crying 14 29
Means (SD) 20.65 (39.99) 137.77 (51.83)
No. Crying 9 29
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RICCILLO AND WATTERSON TABLE 3
MEAN DURATIONS OF CRYING IN SEC FOR THE CONTROL GROUP AND FOR PRESENTATIONOF OTHER-CRY TO THE STIMULUS GROUP BY STATE
Other-cry stimulus Means (SD) Calm Crying
13.26 (29.96) 96.52 (64.70)
Control
No. Crying 9 29
Means (SD) 20.65 (39.99) 137.71 (51.83)
No. Crying 9 29
interaction among the main variables. Thus, presentation of either test cry stimulus appeared to suppress the crying output of the stimulus group even though they did not respond differently to the two test-cry stimuli. DISCUSSION The present study focused on whether or not newborn infants would respond differently to their own cry than to the cry of another newborn infant. The obtained results indicated that the subjects in this study did not differentiate these similar stimuli by crying in greater or lesser amounts. Whether in a calm state, or in a crying state, there was no significant difference in the amount of crying during presentation of either the owncry or the other-cry test stimulus. In that regard, the results stand in contrast to findings reported in previous investigations (Simner, 1971; Martin & Clark, 1982). The differences in findings across studies could be explained, however, by the different experimental methods employed by the different investigators. In the present study, the lack of crying was regarded as a response alternative to overt crying while previous studies have disregarded the lack of crying as a possible response. Like previous investigators, we also noticed that some infants are more likely to cry than others during stimulus presentation, but we found no evidence that their amount of crying could be explained as a discriminative response to our stimuli. Although the subjects in the present study did not appear to discriminate their own cry from the cry of another infant, it did appear that the presentation of the test-cry stimuli influenced their overall cry behavior. When the stimulus group was compared to the control group, statistical analysis showed that the stimulus group cried significantly less than the control group during presentation of either test-cry stimulus for both the calm state and for the crying state. Possibly this reduction in crying during the stimulus presentation reflects suppression of a crying reflex. It is well known that a newborn human infant is dominated by a variety of primitive reflexes that serve primitive needs (Langer, 1969; Gesell,
SUPPRESSION OF CRYING
41
1945; Wolff, 1969; Watson, 1962; Piaget, 1971; Whitaker, 1976). As part of the process of maturation, these primitive reflexes must be suppressed, modified, and/or shaped into volitional behavior (Mysak, 1968; Hardy, 1983). For example, the rooting and sucking reflexes provide the newborn infant with the physiologic basis to obtain liquid nourishment. However, these same reflexes must be suppressed and modified to permit progression to solid food, Crying may be one of the primitive reflexes present at birth, and, like other primitive reflexes, it serves primitive needs. Those needs might include signaling caretakers or obtaining respiratory exercise or a variety of other needs. But, in the course of maturation, the infant must suppress crying because it would interfere with auditory-vocal development and the subsequent progression to more efficient methods of communication. Evidence that crying is a suppressed primitive reflex may be gleaned from the literature on brain-injured adults. Neural lesions in adults may release lower neural centers from the necessary influence of inhibitory mechanisms. This release of inhibition may result in the recurrence of primitive reflexes such as sucking (Truex & Carpenter, 1969; Darley, Aronson, & Brown, 1975; Hardy, 1983). Spontaneous crying is a common symptom of bilateral pyramidal tract lesion (pseudobulbar palsy) (Darley et al., 1975). It seems possible, then, that such symptomatic crying may represent a release of inhibition to a reflexive mechanism that is normally suppressed. Certainly it is difhcult for any individual to receive and perceive auditory stimuli while in the act of generating competing noise. Humans perceive auditory stimuli and humans generate auditory stimuli, but they do not effectively engage in both simultaneously. It may be that the human infant suppresses the crying reflex in the presence of auditory stimuli in order to listen. If that is the case, suppression of the crying reflex may represent the infant’s first “attempt” to interact with its auditory environment. As the primitive nervous system gradually matures, reflexive crying would proportionately decrease in frequency. This decrease in cry occurrences would then permit noncry vocalizations to develop in context-free situations, and these vocalizations would have the potential to develop symbolic meaning (Murai, 1963). Thus, cry suppression may be the neuro-social mechanism that functions as the link between crying and other vocalizations. Possibly, the luck of crying is more important to the development of vocalization than the act of crying itself. REFERENCES Adler, A. 1946. The psychology of early childhood. London: Methuen. Bloom, L., & Lahey, M. 1978. Language development and language disorders. New York: Wiley. Darley, F., Aronson, A., & Brown, J. 1975.Motor speech disorders. Philadelphia: Saunders. Gesell, A. 1945. The embryology of behavior. New York: Harper.
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Gladding, S. T. 1978. Empathy, gender, and training as factors in the identification of normal infant cry signals. Perceptual and Motor Skills, 47, 267-270. Hardy, J. 1983. Cerebral palsy. Englewood Cliffs, NJ: Prentice-Hall. Illingsworth, R. S. 1955. Crying in infants and children. British Medical Journal, 1, 75. Illingsworth, R. S. 1980. The development of communication in the first year and the factors which affect it. In T. Murry & J. Murry (Eds.), Infant communication: Cry and enrly speech. Houston: College-Hill Press. Langer, J. 1969. Theories of development. New York: Holt, Rinehart & Winston. Lewis, M. M. 1951. Infant speech. New York: Humanities Press. Lieberman, P., Harris, K. S., Wolff, P., & Russell, L. H. 1971. Newborn infant cry and nonhuman primate vocalizations. Journal of Speech and Hearing Research, 14, 718727. Martin, G. B., & Clark III, R. D. 1982. Distress crying in neonates. Developmental Psychology,
18, 3-9.
Morley, M. E. 1967. The development and disorders of speech in childhood. Baltimore: Williams & Wilkins. Murai, J. 1963. The sounds of infants: Their phonemicazation and symbolization. Studia Phonologica, 3, 17-34. Mysak, E. D. 1968. Neuroevolutional approach to cerebral palsy and speech. New York: Teachers College Press. Ostwald, P. 1953. Soundmaking: The acoustical communication of emotion. Springfield, IL: Thomas. Piaget, J. 1971. Biology and knowledge. Chicago: Univ. of Chicago Press. Ringel, R. L., KzKluppel, D. D. 1964.Neonatal crying: A normative study. Folia Phoniatrica, 16, 1-9. Simner, M. L. 1971. Newborn’s response to the cry of another infant. Developmental Psychology, 5, 136-150. Truex, R., & Carpenter, M. 1969. Human neuroanatomy. Baltimore: Williams and Wilkins. Wasz-Hockert, O., Lind, J., Vuorenkoski, V., Partanen, T., & Valanne, E. 1968. The infant cry, a spectrographic and auditory analysis. Clinics in developmental medicine, 29, l-42. Watson, J. B. 1962. Behaviorism. Chicago: Univ. of Chicago Press. Whitaker, H. 1976. Neurobiology of language. In E. C. Carterette & M. P. Friedman (Eds.), Handbook of perception. New York: Academic Press. Winer, B. 1971. Statistical principles in experimental design. New York: McGraw-Hill. Wolff, P. H. 1969.Crying and vocalization in early infancy. In B. M. Foss (Ed.), Determinants of infant behavior. New York: Wiley. Vol. IV.