Physiologic Assessment of Mother-Infant Attachment

WILBERTA L. DONOVAN, PH.D., AND LEWIS A. LEAVITT, M.D.

Mother-infant pairs were observed and videotaped in the Ainsworth-Wittig strangesituation, a standard laboratory setting designed to assess the infant's quality of attachment.Concurrent with the video tape recording, heart rates of mother and infant were recordedthroughout the session . Security of mother-infant attachment was reflected in the physio ­logical responses of both mother and infant to the social events of interest in the strangesituation. Securely attached infants exhibited a deceleratory response concurrent withattention to the stranger's entrance and her approach toward the infant. Similarly themothers of these securely attached infants showed an "attentive" response to both theseepisodes. Insecurely attached infants and their mothers failed to show consistent physiologicresponse to either episode. Impending separation from the mother elicited an acceleratoryresponse in both securely and insecurely attached infants even though their behavioralresponses differed.

Journal of the American Academy of Child Psychiatry, 24, 1:65-70, 1985.

The affective bond between infant and mothercalled "attachment" has been studied by Ainsworth etal. (1978) and others using a laboratory proceduretermed the "strange situation." In this procedure, at­tachment is assessed by observing the infant's re­sponse to a stranger's entrance and approach, beingleft alone, and being reunited with his or her mother(Ainsworth and Wittig, 1969).

Ainsworth and colleagues (1978), in their investi­gation into the origins of individual differences exhib­ited by infants in their attachment relationship totheir mothers, have concluded that "sensitive respon­siveness to infant signals and communication seemsto be the key variable accounting for environmentalinfluences on the development of a secure versus aninsecure (anxious) attachment relationship" (p, 152).A number of studies have related maternal sensitivityto the infant's competence (Ainsworth and Bell, 1974;Beckwith et al., 1976; Bell, 1970; Donovan and Leavitt,1978; Sroufe and Waters, 1977a).

The importance of a mother's sensitive responsive­ness for her infant's development led us to study themother's attentional processing of infant signals todetermine its role in the development of differencesin maternal behavioral sensitivity (Donovan et al.,1978). Mothers' attentional processing of signals wasmeasured physiologically. The data indicated thatmothers who showed a greater physiologic response

Received Nov. 24, 1983; accepted Jan . 11. 1984.This research was supported in port by NIH grant HD03352 to

the Wai.~man Center and NIMH grant 31522-01 to the investigators.Portions of these data were presented at the Society for Psycho­physiological Research, Minneapolis, 1982. Requests for reprintsshould be sent to Dr. W. L. Donovan, or Dr. L. A. Leavitt, WaismanCenter, University of Wisconsin-Madison , Madison, WI 53706.

0002· 7138/85/2401-0065 $02.00/0 © 1985 by the American Acad­emy of Child Psychiatry.

65

(cardiac change) to the facial orientations and expres­sions of an unfamiliar infant indeed showed greaterbehavioral sensitivity toward their own infant in afeeding session (Donovan and Leavitt, 1978).

In the present study physiologic measures wereagain recorded, this time to study the attentionalprocessing of securely and insecurely attached mother­infant pairs in the strange situation. Several investi­gators have argued that the concurrent recording ofphysiologic (heart rate) and behavioral observationsis especially useful to more clearly differentiate be­tween such reactions to the stranger as "sobering""wariness" and "fear" (Campos et al., 1975; Waters etal., 1975). Direction of heart rate change has beenused to distinguish between processes that facilitatestimulus intake as opposed to processes that reducethe effects of stimulation-cardiac deceleration beingassociated with an orienting-attentional system, andthe protective-defensive system being associated withcardiac acceleration (Graham and Clifton, 1966; La­cey, 1967). Therefore the direction of cardiac responsecan provide the converging data often necessary forthe interpretation of behavioral responses.

For example, Sroufe and Waters (1977b) reportedcontrasts in the cardiac activity of securely and inse­curely (avoidant) attached infants during "explora­tion." The characteristic intermittent deceleratory re­sponse reflecting attention toward and involvementwith an object which was displayed by securely at­tached infants was not seen in avoidant infants whileplaying with a toy. Additionally, these avoidant in­fants who did not cry during separation or reunion, acommon behavior for other infants, exhibited cardiacacceleration in response to separation as do securelyattached infants. Furthermore, their heart rate re-

66 W. L. DONOVAN AND L. A. LEAVITT

mained accelerated long into the reunion episode,presumably because they were not comforted by thecaregiver as are securely attached infants.

Because of the mother's contribution to the attach­ment relationship, mediated via responsiveness, weinquired whether there are consistent physiologic re­sponse patterns exhibited by mothers in the strangesituation. It is known that behavioral differences insensitivity to infant behaviors differentiate mothersof securely versus insecurely attached infants(Ainsworth and Bell, 1974) with additional behavioraldifferences further differentiating mothers of inse­curely avoidant and insecurely ambivalent infants. Itwould be of considerable importance if one could alsodemonstrate consistent physiologic response patternsdifferentiating mothers of securely attached infantsfrom those labeled as insecurely attached.

Earlier studies (Donovan et aI., 1978; Leavitt andDonovan, 1979) showed infant signals (smile, gaze)elicited consistent maternal physiologic response pat­terns which were predictive of later behavioral sensi­tivity. The infant's averted (e.g., non-face-to-face)gaze was also a potent stimulus eliciting attentionfrom mothers (Leavitt and Donovan, 1979). Collis andSchaeffer (1975) have argued that developing reci­procity is affected by indirect (non-face-to-face) inter­action to the extent that knowledge about the direc­tion of her baby's gaze provides a mother with infor­mation about the future course of the baby's behavior.This information enables her to prepare herself andadapt accordingly. By studying the synchronization ofvisual attention in mother-infant pairs, they demon­strated that attention to environmental events or ob­jects (e.g., toys) plays an important role regulating theinteractive process. In the present study, the infant'svisual exploration of the stranger's entrance and even­tual approach was expected to be attention provokingfor both infant and mother. We predicted that thecharacteristic phasic deceleration associated with at­tention would be exhibited by both mother and infantduring such episodes of dyadic attentional synchroni­zation as during the stranger's entrance and approach.

In summary, we designed the present study to de­termine whether physiologic responses of the infantand its mother accompany important episodes occur­ring within the strange situation, especially duringepisodes predicting the characteristic phasic deceler­ation associated with attention (e.g., stranger's en­trance).

Method

Subjects

The original sample consisted of 37 white, middle­class infants and their mothers. Of these mother-

infant pairs, 29 pairs provided complete physiologicdata on both mother and child as well as behavioraldata on the infant. Of these pairs providing completedata, 14 of the infants were male, and 15 female. Allinfants participated in the study within 5 days of theirfirst birthday.

Apparatus

Both mother and infant were fitted with the elec­trodes for monitoring heart rate. For each, the elec­trodes were attached to the chest with micropore tapeand were connected to a Narco Bio Systems transmit­ter. The mother carried the transmitter in her waist­band; for the infant, the transmitter was securelyfitted in a custom-made foam-padded pocket whichwas attached to a foam-padded belt placed around theinfant.

Signals from each transmitter were received by oneof two FM receivers, each of which was connected toone channel of an Offner Type R Dynograph. Signalswere transduced and amplified by the Dynograph andvia a Vetter FM Model-3 recorder adaptor were re­corded on magnetic tape on a Teac 3300 S recorder.The R-R intervals of the electrocardiogram were timedto the nearest millisecond off line using a PDP-12computer and then converted to heart rate in beatsper minute for each second interval. Analysis of sec­ond by second cardiac responses were made for the 9­sec interval following stimulus onset. By means of afoot pedal connected to the second channel of theTeac 3300 S recorder, an experimenter marked theoccurrence of specific episodes throughout the strangesituation which had been selected for observation ofconcurrent cardiac and behavioral responses. A singleexperimenter determined the "stimulus onset" of eachepisode. The episodes of greatest interest, the stran­ger's entrance and approach, occur early in the sessionbefore the constellation of infant behaviors indicatinga secure versus insecure attachment has emerged.

Procedure

Mother-infant dyads were observed and videotapedin a standard laboratory setting designed to assess theinfant's quality of attachment (Ainsworth and Wittig,1969). Details of the eight episodes comprising thestrange situation are provided elsewhere (Ainsworthet al. (1978), pp. 36-40). The video equipment was notvisible to mother and infant, but mothers were awareof being taped and were assured that the tapes werefor research purposes only.

Concurrent with the video tape recording, the elec­trocardiograms of mother and infant were recordedthroughout the strange situation. In addition to car­diac response to selected episodes of interest, pre- and

PHYSIOLOGIC ASSESSMENT OF MOTHER-INFANT ATTACHMENT 67

4STRANGER'S ENTRANCE

FIG, J. Cardiac response of insecurely and securely attachedin fants to the stranger's entrance.

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and insecurely attached infants and their mothers toselected episodes of interest. Cardiac response to theseepisodes (e.g., stranger's entrance) was determined byexpressing the mean heart rate during each of 9 I-secperiods following stimulus onset as a deviation fromthe mean heart rate during the pre-stimulus second.The second by second tests allowed us to determinewhether deviations from pre-stimulus level were sig­nificant.

Because of the small number of insecurely attachedinfants (group A, N = 4; group C, N = 3), the cardiacdata for securely attached infants (group B, N = 21)will be emphasized and discussed in detail. Cardiacdata of securely attached infants showed considerableconsistency. Securely attached infants from both B2and B3 subgroups responded with consistent cardiacdeceleration to both the stranger's entrance and herapproach. To the stranger's entrance, response on allpost-stimulus seconds was deceleratory. For B2 in­fan ts the second-by-second tests revealed that seconds8 and 9 deviated significantly from pre-stimulus sec­ond, F(l, 5) = 9.73 to 17.28, p < 0.05 to 0.01; and forB3 infants, second 4 showed significant deceleration,F(l, 14) = 6.02, p < 0.05 (see Fig. 1). A deceleratoryresponse was also elicited in securely attached infantsby the stranger's approach. Again all post-stimulusseconds were deceleratory for B2 infants, seconds 4and 5 deviated significantly from pre-stimulus level,F(1, 5) = 7.98,p < 0.05. B3 infants showed pronounceddeceleration on seconds 6-8, F(l, 14) = 6.03 to 12.46,p < 0.05 to 0.005 (see Fig. 2). Since the cardiacresponses of securely attached infants were analyzedby subgroups and because only a single infant was

Results

Cardiac activity (R-R interval from the electrocar­diogram), monitored throughout the strange situation,was converted to heart rate in beats per minute foreach second interval. The heart-rate data were ana­lyzed to determine the response patterns of securely

post-heart-rate levels of both mother and infant weretaken. Selected episodes of interest for the analysis ofthese concurrent measures of cardiac and behavioralresponses of both mother and infant included, first,the stranger's entrance. This episode was marked onthe tape upon full entrance of the stranger. Followingthis entrance the stranger sat and remained seated for2 min. She then rose and approached the infant. Thesecond episode, the stranger's approach to the infant,was marked when the stranger was approximately 1yard from the infant. Other responses of only theinfant selected for analysis were 1) the mother's verbal"goodbye" as she left the room and 2) the mother'sentrance, again marked upon full entrance. Data fromthe mother's second exit and second reunion are notreported because many infants were crying at thispoint.

Following the session and the removal of the trans­mitters, mothers were given the opportunity to discussthe session with the experimenter and each was askedto supply demographic information.

Infant Classification

Two judges viewed the videotapes of each sessionand independently placed each infant in one of theeight subgroups: AI, A2, Bl, B2, B3, B4, Cl, and C2,based upon Ainsworth's description of the pattern­ing of infant behaviors determining classification(Ainsworth et al. (1978), pp. 59-63). Complete agree­ment occurred in 27 of the 29 cases. Of the twodisagreements occurring, one judge placed the infantin the C2 group, and the other judge placed the infantin B4. After conference, a final classification ofsubgroup B4 was made. The other disagreement in­volved placing the infant in the A2 versus the B2group. After conference, a final classification ofsubgroup A2 was made. Thus 22 infants were catego­rized as securely attached and placed in group B (6 insubgroup B2, 15 in subgroup B3, and 1 in B4). Sevenwere categorized as insecurely attached, 4 as avoidantinfants (group A), and 3 as ambivalent (group C). Ourpercentage of infants in each of the three main groupswere in agreement with percentages reported by others(Ainsworth et aI., 1978). For purposes of discussion,infants were usually designated as being either se­curely attached (group B) or insecurely attached(groups A and C).

68 W. L. DONOVAN AND L. A. LEAVITI

significantly on seconds 2, 3, and 6, F(l, 14) = 5.08 to5.68, p < 0.05 (see Fig. 4).

In response to impending separation (i.e., mother'sgoodbye) both securely and insecurely attached in­fants showed an increase in cardiac activity. Theacceleratory response of B3 infants deviated signifi­cantly on seconds 2 and 3, F(l, 14) = 5.28 to 7.89, p <0.05 to 0.025; B2 infants exhibited a biphasic responseto the mother's goodbye with an early deceleration atpost-stimulus second 1, F(l, 5) = 7.45, p < 0.05,followed by a consistent trend toward an acceleratoryresponse on the latter seconds. The insecurely at­tached infants (Groups A and C) also exhibited accel­eration to impending separation, with post-stimulussecond 7 deviating significantly from pre-stimuluslevel, F(l, 6) = 6.18, p < 0.05 (see Fig. 5).

Response of B2 and B3 infants to the mother'sentrance diverged. B2 infants showed an acceleratoryresponse with post-stimulus second 6 deviating signif-

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FIG. 4. Cardiac response of mothers of insecurely and securelyattached infants to the stranger's approach.

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FIG. 5. Cardiac response of securely and insecurely attachedinfants to impending separation from the mother.

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FIG. :1. Cardiac response of mothers of insecurely and securelyattached infants to the stranger's entrance.

categorized as B4, the data of the B4 infant wereconsidered not substantive enough to report.

The mothers' physiologic response at the time ofthe stranger's entrance and her approach toward theinfant was found to be consistent in mothers of se­curely attached infants. The stranger's entrance elic­ited a deceleratory response in mothers of B2 infantswith a significant deviation on post-stimulus seconds2, and 7 through 9, F(l, 5) = 8.03 to 8.76, p < 0.05.Similarly, mothers of B3 infants exhibited a deceler­atory response with significant deviation at post-stim­ulus second 8, F(l, 14) = 6.35, P < 0.05 (see Fig. 3).As to the stranger's entrance, the stranger's approachto the infant elicited a pronounced deceleratory re­sponse in mothers of securely attached infants. Post­stimulus seconds deviated significantly on seconds 6,7, and 9, F(l, 6) = 11.79 to 19.00,p < 0.05 to 0.025 forB2 mothers; response of mothers of B3 babies deviated

PHYSIOLOGIC ASSESSMENT OF MOTHER-INFANT ATTACHMENT 69

icantly from pre-stimulus level, F(l, 5) = 8.37, p <0.05. In contrast, B3 infants responded with pro­nounced deceleration. With the exception of post­stimulus second 9, all showed significant decelerationfrom pre-stimulus second F(l, 14) = 5.61 to 9.60, p <0.05 to 0.0l.

In contrast to these deceleratory (attentive) re­sponses of securely attached infants and their moth­ers, cardiac responses of insecurely attached infantsand their mothers failed to show a consistency ofresponse in these second-by-second tests. Visual in­spection of the individual curves indicated that thislack of consistency was not because members of inse­curely attached groups (ambivalent and avoidant)were combined.

Discussion

Two findings emerged from the present study. Dis­cussion necessarily focuses on the response of securelyattached infants and their mothers because of thesmall number of insecurely attached infants in thesample. First, the cardiac responses exhibited by thesecurely attached infants are in agreement with andextend those of Sroufe and Waters (l977b), whichshow that these infants exhibit periodic cardiac de­celeration concurrent with visual attention. Cardiacdeceleration was correlated with attention observedduring involvement with a toy. In our study, securelyattached infants exhibited a similar deceleratory re­sponse concurrent with attention to the stranger'sentrance and her approach toward the infant.

Additionally, our infant cardiac data complementSroufe and Water's findings that during separationheart rate is elevated in both securely and insecurelyattached infants. In our study we focused on phasicresponses during impending separation. This episodeelicited an acceleratory response in both securely,especially the B3 infants, and insecurely attachedinfants even though their behavioral responses dif­fered.

The second and major finding of the present studyis the physiologic data collected from the mothers.The physiologic response patterns of the mothers ofsecurely attached infants paralleled those of theirinfants. These mothers exhibited phasic decelerationto the stranger's entrance and her approach towardthe infant. The cardiac deceleration of a mother pairedwith a securely attached infant may be interpreted asreflecting an involvement in her infant's behavior.Indeed such involvement may be yet another instanceof maternal sensitivity that affects the attachmentprocess. By noting (and responding to) the directionof the baby's gaze and/or events surrounding herinfant (e.g., the stranger's entrance), a mother displays

a sensitivity which contributes to the development ofa secure attachment relationship.

It is of note that mothers of insecurely attachedinfants failed to show consistency of response to thestranger's entrance and to her approach (see Figs. 3and 4). We speculate that a mother responding in thismanner may reflect less involvement in events sur­rounding and/or influencing her infant's behavior. Alarger sample of mothers of insecurely attached in­fants is needed to determine whether physiologic re­sponse patterns reliably differentiate mothers of in­securely versus securely attached infants as does theirbehavioral response of sensitivity. Our data suggestthis may be the case. Future work on insecurely at­tached dyads will allow us to define similarities anddifferences in physiologic response between contrast­ing groups of insecurely attached dyads, the insecurelyavoidant and insecurely ambivalent groups. In someinstances they would be expected to be similar. Forexample, the particular episodes selected for observa­tion in our study involved attentional processing ofevents surrounding the infant. To the degree that thispredicts behavioral sensitivity it is consistent thatmothers from both groups failed to respond physiolog­ically. On the other hand, characteristic behavioraldifferences of mothers of ambivalent versus avoidantinfants may indeed be correlated with differences inphysiologic response.

The significance of the finding that mothers ofsecurely attached infants respond with an attentive(physiologic) response lies in its implication for theinfant's development. Although differences in mater­nal behavioral sensitivity were not assessed in thepresent study (judgments of secure versus insecureattachments are based on observations of infant be­haviors), the link between maternal behavioral sensi­tivity and attachment behaviors has been provided byothers (Ainsworth and Bell, 1974;Bell, 1970). A secureattachment mediated via relative maternal sensitivityto infants social signals appears to foster an infant'scognitive development (Ainsworth and Bell, 1974;Beckwith et al., 1976; Donovan and Leavitt, 1978;Sroufe and Waters, 1977a). That mothers of securelyattached infants respond physiologically during epi­sodes involving their infant's behavior suggests thatmaternal behavioral sensitivity may reflect a sensorysensitivity (indexed physiologically) to events sur­rounding infant behaviors.

This present finding extends our earlier work em­ploying the use of physiologic indices to the study ofsocial interaction. The infant's development of theobject concept was found to be positively related tomaternal behavioral sensitivity and mothers who werebehaviorally sensitive to infant cues had earlier exhib­ited physiologic response to infant signals (Donovan

70 W. L. DONOVAN AND L. A. LEAVITT

and Leavitt, 1978). Also differences in maternal phys­iologic response to cues signaling the onset of infantcrying have been suggested as a contributing factor tobehavioral differences in stopping infant crying (Don­ovan, 1981). Only mothers with prior experience con­trolling the cry showed cardiac deceleration, an indexof attentional processing, during a signaled LO-seeinterval preceding the cry. This study proposed thatthe learned helplessness theory (Seligman, 1975) serveas a model to account for the observed differences inmaternal behavioral response.

In sum, security of mother-infant attachment asassessed by scoring behavior in the Ainsworth-Wittigstrange situation was reflected also in the physiologicresponses of both mother and infant to the socialevents of interest in the strange situation. Mothersand their securely attached infants showed similarattentive responses to selected episodes. These resultssupport our earlier proposal (Donovan et al., 1978;Donovan and Leavitt, 1978) that mothers' physiolog­ical responses to infant signals characterize styles ofcognitive processing manifested in behavioral contin­gencies during social interaction.

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