Developmental Changes in Infant-Stranger InteractionšΨΑ355... · infants. Strangers were also...

INFANT BEHAVIOR AND DEVELOPMENT 15, 191-208 (1992)

Developmental Changes in Infant-Stranger Interaction

SARAH C. MANGELSDORF

Universily of Illinois

Although considerable attention hos been given to the phenomenon of “stranger anxtety,” we still do not know some of the behavior01 characteristics of strangers associated with infonts’ wariness of strongers and how these may change wtth development. We olso have not systemoticolly examined the woys in which adults may vary their behavior OS o functron of the oge of the child. The following study addresses these issues. Seventy-five Infants (25 in each group of 6, 12-, ond l&month-olds) were videotaped interacting with three strongers sequentially. One stranger (the “standard stranger”) interacted with 011 of the infants first. The other strangers (N = 50) each interacted with three infants, one from each oge group. The videotapes were coded for venous aspects of infant and stranger behovior. Six-month-olds were more positive with strongers who showed more positive affect ond who did not touch them. In contrast, 12- ond 18-month-olds’ reactions were related to aspects of the stranger behovior such as controllability and sensitivity. Strangers behoved very differently with 1%month-olds than with the younger infonts, allowing them more control in the interaction. Moternol reports of their infonts’ reactions to strangers obtained before the loboratory visit were significantly related to infant behavior observed in the lob.

emotional development stranger wariness

Few developmental phenomena have attracted as much attention as fear of strangers in infancy, yet in many ways we know relatively little about the phenomenon. There is a great deal of individual variation in stranger wariness both in terms of behaviors manifested and their onset and duration. In fact, some researchers have argued that infants are not afraid of strangers (e.g., Rheingold & Eckerman, 1973), claiming that positive social responses to strangers are more common than fear responses in the first year of life. However, if one looks for signs of wariness (e.g., gaze aversion), as well as outright fear, a generalized phenomenon is evident (Sroufe, 1977). This

While conducting this research, the author was supported by a dissertation fellowship from

the Graduate School at the University of Minnesota. The author thanks all those who helped in

this research, including Julie Friedman, who served as the “standard stranger.” and Debra

Andreas. Jamalee Erickson. and Michelle Nerzerka. who helped with the coding. Thanks also to

Toni Antanucci. Eugene Borgida. Byron Egeland, Megan Gunnar. Willard Hartup, Roberta

Paikoff, Karl Rasengren, Alan Sroufe. and Stacey Watkins. as well as the anonymous reviewers,

who read and commented on drafts of this article. Portions of these data were presented at the

lntcrnational Confcrcnce on Infant Studies, Washington, DC, 1988.

Correspondence and requests for reprints should be sent to Sarah Mangelsdorf. Department

of Psychology, University of Illinois. 603 E. Daniel Street, Champaign. IL 61820.

191

192 MANGELSDORF

variability in infants’ responses to strangers may be explained in part by temperamental variation among infants. In addition, it may be that variation in the behavior of strangers may explain differential responding. For example, infants may actively appraise strangers’ actions, and this appraisal may influence their responses. Many theories of emotion, which emphasize the importance of appraisal or evaluation processes in determining emotional reactions (Campos, Barrett, Lamb, Goldsmith, & Stenberg, 1983; Ekman, 1984; Lazarus, 1984; Lewis & Brooks-Gunn, 1979; Sroufe, 1979), would suggest that infants may actively appraise or evaluate strangers’ actions, and this appraisal may influence their responses. However, it is important to note that appraisal or evaluation cannot be observed directly, particularly in infancy. Thus, although some theorists would suggest that appraisal or evaluation can be inferred from the child’s emotional reactions to events, others would suggest that the use of such terms is inappropriate when discussing infants. In this case, it may simply be best to discuss the characteristics of stranger behavior associated with infants’ responses.

Some research exists on the effects of the physical characteristics of strangers on infants’ responding. Infants respond more positively to shorter than to taller strangers (Brooks & Lewis, 1976), female than male strangers (Clarke- Stewart, 1978; Lewis & Brooks, 1974), and attractive than unattractive strangers (Langlois, Roggman, & Rieser-Danner, 1990). There is less research concerning the effects of variations in stranger behavior on infant responding. However, there are data indicating that rate of approach is an important variable (Ainsworth, 1973; Ricciuti, 1974; Ross & Goldman, 1977a), with infants responding more positively to strangers who approach them slowly. Likewise, there is evidence that infants prefer “active” strangers, who play with them, to “passive” strangers who just look at them (Bretherton & Ainsworth, 1974; Clarke-Stewart, 1978; Ross & Goldman, 1977). Some researchers have noted, in reviewing studies in this area, that the “standardized stranger approach sequence” used in many studies typically is met with more negative reactions than situations in which the strangers are more spontaneous and more responsive to infant cues (Clarke-Stewart, 1978; Horner, 1980). This has been attributed in part to the extent to which the young child has control over the stranger’s behavior. Thus, a number of researchers have suggested that stranger intrusiveness and uncontrollability may contribute to stranger fear or wariness (Bronson, 1972; Horner, 1980; Morgan & Ricciuti, 1969; Sroufe, 1977). Levitt (1980) attempted to examine this empirically by studying the effects of infants’ ability to control the appearance/disappearance of a stranger in a puppet-stage and found that infants exhibited more positive affect when they were able to control the stranger’s appearance. In a pilot study with lo-month-olds, Mangelsdorf, Lehr, and Friedman (1986) noted that there was a positive association between the amount of control that strangers allowed infants in interactions and

INFANT-STRANGER INTERACTION 193

how positive the infants’ responses were. On the whole, however, we know very little about which stranger behaviors are associated with the infant’s responses in more naturalistic interactions. These descriptive data are needed in order to establish a theory of stranger wariness that can account both for the emergence of the phenomenon and for the variation in infants’ responses across strangers.

This study was conducted in order to obtain descriptive data using natu- rally occurring (not experimentally imposed) differences in behavior among strangers. The subjects in this study were 6-, 12-, and 18-month-old infants, an age span in which stranger wariness has been noted (Sroufe, 1977). Infants of all three of these ages were observed interacting with three adult females. Aspects of the strangers’ behavior were coded and correlated with measures of the infants’ emotional response. Stranger behaviors selected for coding were derived from the literature on stranger wariness (e.g., rate of approach), the literature on infant fear more generally (e.g., predictability and control), and mother-child interaction literature (e.g., sensitivity). In addition, in order to examine differences among infants in their temperaments or typical wariness of strangers, maternal reports of stranger wariness were obtained. Finally, although there is evidence that older infants may be more active in initiating interaction with strange adults (Bretherton, Stolberg, & Kreye, 1981), there has been little systematic investigation of how strangers may alter their behavior when interacting with infants of different ages, thus, in this study, differences in stranger behavior were examined as a function of the age of the child.

METHOD

Subjects and Design Seventy-five infants, 25 each at 6, 12, and 18 months (39 females, 36 males), from middle-class homes were videotaped interacting sequentially with three female strangers. The strangers were women ranging in age from 19 to 35 years who had no children of their own. One stranger, a 21-year-old (the “standard stranger”), interacted with all of the infants first. Reactions to this stranger were used to make direct comparisons among infants in their typical wariness of strangers. All other strangers interacted with three infants, one from each age group. A variety of strangers naive to the study’s purpose were used because it was expected that adult females would get better at eliciting positive reactions from infants with practice. By limiting “practice” in this study to three infants, it was hoped that variability in behavior among strangers would be preserved. Thus, there were 25 pairs of strangers in addition to the standard stranger. All strangers except for the standard stranger were randomly assigned to interact with infants either second (Trial 2) or third (Trial 3). Thus, if a stranger was assigned to be a Trial 3 stranger, she would

194 MANGELSDORF

be a Trial 3 stranger for all three of the infants with whom she interacted, and the woman who was the Trial 2 stranger would precede her for all three infants. Strangers were also randomly assigned to interact with infants of different ages, that is, some strangers interacted with a 6-month-old first, some with a 12-month-old, and some with an l&month-old. As a warm-up period, the infants interacted with their mothers for the first 8 min of the session. This was followed by 8-min interaction episodes with each of the three strangers, interspersed by 2-min breaks between strangers.

Procedures One week before the scheduled visit to the laboratory, mothers were mailed a 6-item stranger reaction questionnaire (see below) which they completed and returned at the time of testing. When the mother and infant arrived at the laboratory, they were shown into a 4.57 m x 4.57 m (15 ft x 15 ft) testing room with a one-way mirror. The mother and infant were given 8 min to play and adapt the infant to the room. Two toys, a boat and a truck, were available at this time. At the sound of the knock on the mirror, the mother took her seat in the corner of the room, and the first (standard) stranger entered. The mother was instructed to interact minimally with the strangers and to be supportive, but not to initiate interaction with the infant. (Because 6-monttr- olds could not crawl, mothers were told to approach and pick up 6-month- olds if they cried. If the mother failed to do so after 15 s of crying, the experimenter instructed her to do so.) Each stranger brought an identical bag of toys (containing two ring stacks, plastic stacking cups and large pop- beads). The strangers were told only that they were to make friends with the infant, offer toys, play peek-a-boo and “I’m gonna get you” (a tickling game). These games provided a basis of comparison across strangers. In addition, because “I’m gonna get you” involves tactile contact, it must be performed with care in order to elicit a positive response. Strangers knew it was time to leave when they heard a knock on the mirror at the end of the S-min period.

Typical Responses to Strangers. A measure of typical reactions to strangers was derived from the stranger reaction questionnaire. This questionnaire contained six items, each with a 6-point scale, from the Toddler Tempera- ment Scale (TX; Fullard, McDevitt, & Carey, 1984): (a) the child smiles when played with by unfamiliar adults, (b) the child approaches (reaches or moves toward) new visitors at home, (c) the child speaks (or vocalizes) right away to unfamiliar adults, (d) the child is outgoing with adult strangers outside the home, (e) the child’s initial reaction at home to approach by strangers is acceptance (looks at, reaches out), and (f) the child is still wary of strangers after 15 min (reverse-scored). Responses to these items were summed and averaged with high scores reflecting more positive reactions.


Inter-item correlations ranged from r(74) = .25 to .68, M = .44. with a Cronbach’s alpha of .82.

Infant Scales. The infant-stranger sessions were videotaped and later coded by three sets of independent coders. Two coders rated infants’ initial reaction (a global rating of the infant’s initial reaction, ranging from 1 = negative to 3 = neutral or mixed reaction to 5 = positive) during the first minute of each session. Two coders rated infant behavior during the last 4 min of the session, and two coders rated stranger behavior during the first 4 min. Videotapes of pilot sessions were used to develop 5-point infant and stranger behavior scales. These scales were revised versions of scales used in an earlier study upon which the present study was based (Mangelsdorf, Lehr, & Fried- man, 1986). The infant scales included: (a) quality of play (the extent to which the child was engaged in reciprocal play with the stranger), (b) bodily posture (the extent to which the infant’s posture was relaxed and movement was loose and fluid, rather than tense and constrained), (c) proximity-seeking with stranger (the extent to which the child either avoided or approached the stranger, (d) positive affect (the extent to which the child expressed positive affect by smiling or laughing), (e) negative affect (the extent to which the infant expressed negative affect by frowning, whimpering, or crying), (f) proximity- and contact-seeking with mother (the extent to which the infant sought proximity and contact with the mother, and (g) overall reaction (a global rating of the infant’s overall reaction, ranging from 1 = negative to 3 = neutral or mixed reaction to 5 = positive). The proximity-seeking with stranger scale was a modification of a scale developed by Ainsworth (Ainsworth, Blehar, Waters, & Wall, 1978). With the exception of negative affect, which was subsequently reverse-scored, high points on the scales reflected happy, relaxed, and very positive reactions to the strangers. Interrater agreement within 1 scale point ranged from 92% to 100% (M = 97%); Cohen’s kappas ranged from .52 to .92 (M = .73). In order to create a summary score and to determine how the associations among the various infant behaviors might differ as a function of infant age, descriptive varimax factor analyses of infant behavior during the last 4 min were conducted separately at each age for each stranger. All analyses revealed only one factor, but with different loadings at each age. Factor weights were averaged across the three strangers and multi- plied by the infant scale scores to create a summary later reaction score at each age.

Stranger Scales. Stranger behavior was coded using the first 4 min of the 8-min interaction episode. Coders of stranger behavior used the following 5-point stranger scales: (a) predictability (the extent to which the stranger’s behavior was predictable rather than sudden or abrupt), (b) pacing (the degree of “mesh” between the stranger’s and the infant’s tempo, a higher

196 MANGELSDORF

score reflected a more appropriate pace), (c) control (the extent to which the stranger allowed the infant to control the interaction or controlled the interaction herself), and (d) sensitivity (the extent to which the stranger was sensitive to the infant’s signals and responded appropriately). These aspects of stranger behavior were chosen based on prior research on infants’ reactions to novel stimuli, both animate and inanimate. The sensitivity scale was a modified version of Ainsworth’s sensitivity scale (Ainsworth et al., 1978). Intercorrela- tion among these scales ranged from .54 to .67 (M = .58) for 6-month-olds, .58 to .73 (M = .67) for 12-month-olds, and .51 to .70 (M = .60) for 18- month-olds. Interrater agreement on these interactive stranger scales within 1 scale point ranged from 96% to 100% (M = 99%). Cohen’s kappas ranged from .62 to .77 (M = .68). Because these four scales were fairly highly correlated, the scale scores were summed and averaged to yield one stranger behavior summary score. Cronbach’s alphas for this scale were .84 at 6 months, .87 at 12 months, and .86 at 18 months.

In addition to the interactive rating scales, discrete aspects of the stranger’s behavior that did not rely on reference to the infant’s actions were scored. These measures included: (a) stranger’s negative affect (the extent to which the stranger expressed negative affect such as a negative tone of voice or frowning, scored on a 5-point scale, (b) stranger’s positive affect (the extect to which the stranger smiled and laughed during interaction with the infant), (c) time to within one arm’s length of the infant (in seconds), (d) time to first touch of the infant (in seconds). For both time to within one arm’s length and time to first touch, strangers received a score of 250 (seconds) if they either did not come into within one arm’s length of the infant, or if they never touched the infant. The negative affect scale was not included in subsequent analyses because only one of the strangers ever expressed any signs of negative affect. The percent agreement within 1 scale point for positive affect was lOO%, Cohen’s kappa, .55. Pearson correlations were computed for the timed measures; they were time to within arm’s length, r = .88, and time to first touch, r = .88.

Coders of strangers scored the first 4 min of each interaction session, and with the exception of initial reaction coding, infant coders scored the second 4 min in order to: (a) make the assessments of infant and stranger behavior as independent as possible, and (b) allow time for infants to respond to each stranger. All disagreements of greater than 1 scale point were resolved through conference. Disagreements of 1 scale point were averaged. All infant-stranger interaction sessions (N = 225) were assigned random num- bers and were coded in random order. No two sessions with the same infant or the same stranger were coded sequentially, thus reducing the possibility that coders’ assessments of the infant’s or stranger’s behavior would be influenced by how they had seen them behave previously.


TABLE 1

Correlotions of Infonts’ Reactions Across Three Strangers

6-Month-Olds 12-Month-Olds 1%Month-Olds

2nd 3rd 2nd 3rd 2nd 3rd

lnitiol Reaction

To stondord stronger

To 2nd stronger

- .23 .12 .63”’ .46” .80*** .53**

.37’ .48** .53**

toter Reaction

To standard stronger

To 2nd stronger

.76”’ .52** .19 .07 .40 .67”’

.70”’ .29 .67”’

* / - J < .05. l * p < .Ol. *** p < .001

RESULTS

Variability of Infant Reactions In order to determine the extent to which the infants were stable in their reactions across strangers, infant’s later reaction scores were correlated across strangers for each age group. Significant correlations indicative of stability were noted at 6 and 18 but not at 12 months. In addition, the stability of initial reactions was examined by correlating across strangers. In this case, stability was found at 12 and 18 months but not at 6 months (see Table 1).

In order to examine the stability of infants’ reactions within the interaction sessions, the correlations between infants’ initial and later reactions were computed. These correlations revealed significant associations between initial reactions and later reactions for infants of all three ages. What is also noteworthy is that there are significant associations between the later reaction with the standard stranger and the initial reaction with the second stranger, and similarly between the later reaction with the second stranger and the initial reaction with the third stranger for infants of all three ages. This indicates that there was some carry-over from one interaction episode to another. However this carry-over effect seemed to be related to initial reactions and not to later reactions (see Table 2, p. 198).

To examine the extent to which stability, or the lack of it, across strangers in the testing situation was consistent with infants’ typical reactions, correlations were computed between both the initial reaction scores and the later reaction scores and maternal reports of the typical stranger reactions. Signifi- cant correlations were noted at ail three ages, particularly when the reaction scores were averaged over the three strangers with whom the infant interacted (see Table 3, p. 199).

198 MANGELSDORF

TABLE 2

Correlations Between infant’s Initial and toter Reactions

Later Reaction

Initial Reaction

6 Months

Standard stronger

Stranger 2

Stranger 3

ss s2 s3

.45’ .26 .21

SO” .44’ .30

56” .50** .41*

12 Months

Standard stranger .63”’ .32

Stranger 2 .55** .40’

Stronger 3 .12 .63*

I8 Months

Standard stranger .62”’ .30

Stranger 2 .70*** .44’

Stranger 3 .50” .35*

Note: SS = Standard Stronger, S2 = Second Stranger, S3 = Third Stranger * p i .05. ** p < .Ol. *** p < ,001.

.I5

.43’

.26

.56*

.65”’

.70*

Trial and Age Effects

Infant Behavior. Using the variables that comprised the later reaction summary score as dependent variables, 3 (Age) x 3 (Stranger) analyses of variance were calculated. (Preliminary analyses using f tests indicated no significant sex differences for any of the infant or stranger variables.) These ANOVAs and post-hoc Newman-Keuls tests revealed that play, positive affect, negative affect, and proximity to mother yielded significant age effects. Six-month-olds played less, F(2, 72) = 13.10, p < .OOl, showed less positive affect, F(2, 72) = 5.20, p < .Ol, more negative affect, F(2, 72) = 13.10, p < .OOl, and were less likely to seek proximity with mother than 12- and 18- month-olds, F(2, 72) = 9.20, p < .OOl, whereas posture, proximity to stranger, and overall response did not show significant age effects. There were also significant trial effects, with the play of infants of all ages declining from Trial 1 to Trial 2, F(2, 72) = 3.53, p < .05. Infants of all three ages sought more proximity with mother with each trial, F(2,72) = 7.59, p < .OOl, and showed more negative affect in Trial 3 than in the other two trials, F(2, 72) = 9.56, p < .OOl. They also exhibited less relaxed posture, F(2, 72) = 3.35, p < .05, and were rated as having a less positive overall reaction to the stranger in Trial 3 than in Trial 1, F(2, 72) = 9.77, p < ,001. There were no significant age by trial interactions (see Table 4, p. 200).


TABLE 3

Correlations of Motemol Reports With Infant’s lnitiol Reaction and Later Reaction Scores

6-Month-Olds

Moternol Reports

12-Month-Olds 18-Month-Olds

Initial Reaction to:

Stondard stronger

Trial 2 strangers

Trial 3 strangers

Averoge Initial Reaction

.57** .39* .20

.03 .42* .25

.lO .33 .42*

.32 .46* .35*

Infant’s toter Reaction to:

Standard stronger

Trial 2 strangers

Trial 3 strangers

Averoge Later Reaction

* p < .05. l * p < .Ol.

.41’ .44* .53”

.31 .17 .ll

.43* .43’ .58*’

.40’ .53* .48*

Strunger Behavior. In order to examine whether stranger behavior varied systematically as a function of the age of the child, 2 (Stranger) x 3 (Age) analyses of variance were conducted using the various stranger behaviors as the dependent variables. Only the data from the second and third strangers were used because the standard stranger was only 1 rather than 25 individu- als. Newman-Keuls post-hoc tests were used to examine significant age effects. These analyses revealed no significant effects of trial on behavior, that is, strangers 2 and 3 did not differ significantly from one another on any of the stranger variables. There were, however, a number of significant age effects: Strangers approached 1%month-olds more slowly than 6- and 12-month-olds, were slower to touch 1%month-olds than younger infants and slower to touch 12-month-olds than 6-month-olds, smiled less at 6-month-olds than at older infants, and were rated as more sensitive, less controlling, and as moving at a more appropriate pace when interacting with 18-month-olds than with younger infants (see Table 5, p. 201).

Correlates With Stranger Behavior In Table 6 (p. 202), the correlation between infant reaction scores and the stranger behavior measures are shown computed separately for each age and each stranger trial. The correlations for Trial 1 reflect relations between infant reactions and variations across infants in the behaviors of the standard stranger, whereas correlations for Trials 2 and 3 reflect relations between

TABL

E 4

Mean

s an

d St

anda

rd De

viatio

ns

of

Infa

nt

Beha

viors

6 M

onths

12

M

onths

18

M

onths

ss

s2

s3

ss

s2

s3

ss

52

53

Age

Effe

cts

Trial

Ef

fects

Play

2.2

2.0

1.6

3.3

3.2

3.4

4.1

3.6

3.2

6 <

12

8.

18”’

Tl

> T2

&

T3’

(1.51

(1

.3)

11.4)

10

.9)

0.11

W

I IO

.81

11 .O

l (1

2)

Pastu

re

3.7

3.4

3.2

3.8

3.8

3.5

3.9

3.7

3.7

n 5.

Tl

>

T3’

Il.21

11

.31

11.3)

IO

.71

(0.7

1 (0

.71

to.7

1 lo

.81

(0.7

1 Pr

oxim

ity

lo str

ange

r 3.3

3.3

3.0

3.3

2.9

3.0

3.6

3.0

3.0

n.s

n.

s.

WI

(1.31

il.

11

(0.9

1 (1

.01

Il.11

(0

.9)

(1 1

1 (I.

11

Posit

ive

affe

ct 1.7

1.6

1.7

2.4

2.3

2.0

2.4

2.1

2.2

6

< 12

&

18”

“.S.

IO.8

1 (0

.81

IO.8

1 (0

.91

(0.91

(0

.81

(1.1)

(1 .ot

10

.9)

Nega

tive

affe

ct 2.5

2.9

3.2

1.4

1.4

20

1.4

1.6

2.1

6

> 12

&

18”’

Tl

& T2

<

T3”’

(1.7)

(I.

71

(1.4

(0.8

) 10

.81

(1.4

1 Il.

01

11 0

1 11

.a

Prox

imity

to

m

other

1.7

2.0

2.2

2.6

3.2

3.4

2.7

3.5

3.6

6

< 12

&

18”’

Tl

< T2

<

T3”’

0.41

Il.

51

11.7)

Il.5

1 Il.

4 (1

61

(1.6

1 (1

.4

(1.6

1 Ov

erall

3.1

2.7

2.5

3.5

3.1

2.9

3.7

3

1 3.0

n-

s. Tl

>

T3*‘*

Il.11

(1

.4)

(1.4

1 (0

.9)

(1

11

(1.2

1 (1.

11

(1.3

) il.

11

Note:

St

anda

rd de

viatio

ns

appe

ar in

paren

these

s. SS

=

Stan

dard

Qron

ger,

52

= Se

cond

St

rang

er,

S3

= Th

ird

Stra

nger

l

p <

.05.

**

p <

.Ol.

l **

p <

.OO

l.

TABL

E 5

Mean

s an

d St

anda

rd De

w&ion

s of

St

rong

er

Beha

vior

in the

Fi

rst

4 Mi

n

Sens

itivity

Pr

edict

ability

Co

ntrol

Pocin

q Po

sitive

Af

fect

Tim

earm

Ti

me

to

Touc

h

Ston

dard

Stra

nger

6 m

onths

3.3

(0

.6)

3.5

(0.7)

3.4

(0

.7)

3.2

(0.6)

2.6

(0

.8)

9.0

(3.4)

15

8.6

(101

.9)

12

mon

ths

3.7

(0.7)

4.0

(0

.8)

3.7

(0.5)

3.6

(0

.9)

3.2

(0.5)

13

.2 (8

.1)

242.9

(3

5.4)

18

mon

ths

3.8

(0.5)

3.9

(0

.7)

3.8

(0.5)

3.7

(0

.8)

3.4

(0.7)

21

.2 (2

2.5)

238.4

(4

4.0)

Stra

nger

s 2

& 3”

6 m

onths

3.0

(1

.1)

3.5

(1.1)

3.0

(1

.2)

3.7

(1.1)

3.0

” (1

.1)

16.1”

(1

9.1)

94.0

(95.1

)

12

mon

ths

3.3

(1.0)

3.6

(1

.O)

3.3

(1.1)

3.6

(1

2)

3.4

(0

.8)

30.5

(44.3

) 12

9.5

(94.7

)

18

mon

ths

3.7”

(1.1)

3.9

(1

.O)

4.lb

(1.1)

4.0

” (1

.O)

3.5

(1.1)

38

.3 (5

5.2)

174.0

b (9

6.1)

Note.

St

anda

rd de

viatio

ns

appe

ar in

paren

these

s. Tr

mea

rm

= se

cond

s to

wi

thin

one

arm

’s len

gth

of

the

infon

t, str

ange

r rec

ewed

sc

ore

of

250

if sh

e did

no

t m

oke

close

op

prooc

h. Ti

me

to

Touc

h =

seco

nds

until

stran

ger

touch

ed

the

infan

t; str

ange

r rec

eived

sc

ore

of

250

if sh

e did

no

t tou

ch

the

infan

t. o

Beca

use

the

mea

ns

of

Stra

nger

s 2

and

3 did

no

t sig

nifica

ntly

differ

fro

m

one

anoth

er,

the

aver

age

of

the

two

is pre

sente

d he

re b

Mean

dif

fers

signif

icantl

y fro

m

the

other

tw

o.

202 MANGELSDORF

TABLE 6

Correlations Behveen Infont’s Later Reaction and Stranger Behavior

6 Months 12 Months 18 Months

1 2 3 1 2 3 1 2 3

Discrete

TImearm .19 -.25 -.09 -.04 -.03 .59*" -.16 -.25 -.31

Touch .44** .16 .40' .28 .09 .47** -.ll -.12 -.27

Positive affect .43* .49** .08 .04 .29 .39* .33* .oo .35*

lnteroctive stranger

behavior .24 .13 -.02 .68"' -.15 .53*' - .Ol .39* .33*

* p < .05. ** p < .Ol. *** p < .OOl

infant reactions and the behavior of different strangers. The association between infants’ initial reactions and strangers interactive behaviors were also examined. No significant correlations were found between initial reactions and stranger behavior at any of the three ages with any of the three strangers.

At 6 months, infant’s later reaction was not significantly related to the global rating of stranger interactive behavior with any of the three strangers. The 12-month-olds’ later reactions were significantly correlated with stranger interactive behavior for the standard and third strangers, whereas for the 18- month-olds, later reactions were correlated with stranger behavior with the second and third strangers. To examine whether these correlations were significantly different for the three ages, the correlations were averaged across the three strangers for the three different age groups, and significance tests were performed using Fishers’ r to 2 transformations (Hayes, 1981). These tests indicated that there were no significant age differences in the correlations for the discrete behaviors. There was however a significant age difference in the interactive behaviors, with 6-month-olds’ correlations between stranger behavior and infant reactions differing significantly from 12- month-olds’ (6 vs. 12 months, Z = 3.00, p < .OOl). The correlations of 12- and 1%month-olds were not significantly different from one another, Z = 1.80, p < .lO, nor were the correlations of the 6- and l&month-olds, z = 1.30, p > .05.

In order to attempt to control for the effects of infant temperament on infant responding, a measurement of infant temperament was computed by adding together the mothers’ reports of typical reactions to strangers and the infants’ initial reactions to the standard stranger. Initial reaction was used because it represents the infant reaction before the stranger has had much of an opportunity to influence the infant’s response and is thus more likely to represent typical reactions to strangers. The data from the standard stranger were used because she was the only stranger with whom all infants interacted and she was the first stranger with whom all infants interacted. Partial correla-


TABLE 7

Partial Correlations Between Infant’s Later Reaction and Stranger Behavior Controlling

far Infant Temperament

6 Months 12 Months 1 B Months

1 2 3 1 2 3 1 2 3

Discrete

Timeorm .30 -.15 -.lO - .Ol -.03 57" -.03 -.21 -.30

Touch .27 .17 .41' .20 .lO .52** -.15 -.12 -.21

Positive affect .26 .4B" .14 .03 .29 .35* .ll .03 .14

Interactive stranger

behovior .18 .12 .08 .66*** -.18 .58*** .30 .42* .33*

l p < .05. ** p < .Ol. *** p < ,001

tions were computed between infants’ later reaction and stranger behavior, partialling out the temperament measure (see Table 7).

These partial correlations revealed that the general pattern of association remained similar for the correlations between infant’s later reactions and the global ratings of interactive stranger behaviors. However, rather than 13 significant associations with the strangers’ discrete behaviors, only 9 remained significant after controlling for infant temperament. For example, the earlier finding of an association between strangers’ and infants’ positive affect at 18 months was no longer significant.

DISCUSSION

Infants’ Responses to Strangers The results of this study indicate that infants’ reactions to strangers are related to strangers’ behavior, but that the aspects of the strangers’ behavior associated with infant responding vary as a function of the age of the child. The results also indicate, however, that adults alter their behavior as a function of the age of the child. In addition, there appear to be age differences in the stability of infants’ reactions across strangers. Finally, maternal reports of infant temperament are predictive of infant behavior when interacting with strangers.

Many investigations of infants’ wariness of strangers have noted that 6-month-olds are not yet wary of strangers (Emde, Gaensbauer, & Harmon, 1976; Morgan & Ricciuti, 1969). The data indicate that 6-month-olds display less positive affect and more negative affect and play less with strangers than older infants, but they are generally no more tense in their body posture, nor were they rated as more negative in their overall reaction. The global ratings of stranger behavior did not appear to be related to infant responding among the 6-month-olds. However, two discrete aspects of stranger behavior did

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seem to be related to the quality of infant responding: time to first touch and stranger’s positive affect. A number of theorists (Bronson, 1972; Sroufe, 1979; Waters, Matas, & Sroufe, 1975) have proposed that affective reactions within the first 6 months are based primarily on level of arousal rather than on active cognitive appraisal. Indeed, some theorists have attributed the emergence of stranger wariness between 8 and 12 months to changes in cognitive capabilities during the second half year of life, in particular, to changes in the object concept, self-permanence, and understanding of means-ends relations (Kagan, 1974; Lewis & Brooks-Gunn, 1979; Sroufe, 1979). The fact that 6-month-olds appeared happier with strangers who smiled a lot is not incon- sistent with the findings from research on perception of emotion that indicate that infants younger than 6 months prefer smiling faces to nonsmiling faces (Nelson, 1985).

The behavior of the 12- and 18month-olds is correlated with the global rating of stranger behavior for two out of the three strangers, whereas this was not true for the 6-month-olds. Two components of the global stranger behavior rating, control and predictability, are central to the literature on fear and stress in animals and in human adults (e.g., Seligman, 1975). There are also data which indicate that both control (Gunnar-von Gnechton, 1978; Levitt, 1980) and predictability (Gunnar, Leighton, & Peleaux, 1984) moder- ate fear reactions to arousing events by the end of the first year. This is when some researchers have targeted the transition from affect based primarily on the intensity or arousing qualities of stimulation to affect based on the appraisal of the meaning of stimulation (Parritz, Mangelsdorf, & Gunnar, 1992; Sroufe, 1979). Factors such as control do not alter the intensity or quality of stimulation; for control to have an impact, it must alter the meaning of the event. Thus, the fact that these aspects of stranger behavior are associated with infants’ reactions indicates that some sort of appraisal or evaluation may be involved in stranger response by 12 months of age. Al- though the data are consistent with an interpretation related to changes in cognitive capabilities in the second half year of life, because indices of cognitive competence were not directly assessed in this investigation, this assumption cannot be directly tested, and other interpretations are certainly possible.

Age-Related Differences in Stranger Behavior It is important to note that infants do not merely respond to strangers: Strangers are interactive partners who respond to infants’ behavior. One systematic way in which the adults in this study varied their behavior was a function of the age of the child. The strangers treated 18-month-olds much differently than they treated the younger infants. They were more sensitive, less controlling, interacted at a more appropriate pace, and were slower to approach and less likely to touch the 18-month-olds than the younger infants.


This is particularly noteworthy given that differences in appearance and motor development are far greater between the 6-month-olds and the older infants than between the 12- and l&month-old infants. For example, many of the 6-month-olds were not even sitting up, whereas most of the 12- and 18- month-olds were standing and walking. In addition, l&month-olds did not differ from 12-month-olds on any of the behavioral measures assessed in this study. However, there is evidence from other investigations that 18-month- olds do differ from younger children in the extent to which they initiate social interactions and engage in verbal interactions (Bretherton et al., 1981). Anecdotally, it was noted by the coders of stranger behavior that many of the 18-month-olds “took control” of the interaction. A number of researchers (Hornik, 1989; Kopp, 1989) have discussed that by 18 months of age, infants are more active in their attempts to control their environment. Strangers who allowed infants to do this were scored as “less controlling” than strangers who felt compelled to control the interaction; likewise, in responding to infant verbalizations and requests, these strangers would be seen as responding sensitively to the child’s needs.

Changes in Infant Behavior Across Strangers It is clear that infants of all three ages altered their behavior and became generally less positive across the three trials. Infants of all three ages exhibited less play, less relaxed posture, more negative affect, and more proximity- seeking with their mothers across trials. It is not surprising that there is a cumulative fatigue affect of interacting with three strange adults. What is noteworthy, however, is that this fatigue effect is consistent for all three age groups. One might anticipate that, with age, children would become better equipped to deal with longer periods of social stimulation. This did not appear to be the case, at least in this context.

Stability of Infant Reactions One finding of note was that the stability of infants’ initial reactions differed from the stability of later reactions. In particular, 6-month-olds’ initial reactions were not very stable across strangers, although their later reactions were. And 12-month-olds, whose initial reactions were fairly stable, had later reactions which were less stable. Eighteen-month-olds exhibited similar patterns of stability both initially and later. One possible interpretation of these findings is that 6-month-olds’ behavior is not nearly as organized as the behavior of older infants, and thus they take longer to exhibit any observable reaction to strangers. On the other hand, 12-month-olds may have initial greeting behavior that is somewhat automatic and gives way to more discrimi- nating evaluations of individual strangers. Finally, l&month-olds may exhibit categoric reactions to strangers which are discernable within the first minute of interaction, perhaps due to the stability of their behavior. Other research

206 MANGELSDORF

indicates that typical response patterns, or temperamental differences, tend to stabilize over the course of the second year (Matheny, Wilson, & Nuss, 1984).

It is clear that individual differences in infants’ typical reactions to strangers did contribute to the infants’ responses observed in the laboratory. Al- though lZmonth-olds’ responses were less stable across strangers than the 6- and 18-month-olds’ responses, the average stranger response was related to the infants’ typical responses to strangers as reported by the mothers. When the infants’ later responses were averaged across all three strangers, the relations with the maternal reports of typical reactions to strangers (see Table 3) were significant at all three ages. When infants’ typical reactions were controlled for, associations among the global ratings of stranger behavior and the global ratings of infant behavior remained much the same, indicating that infants’ typical responses to strangers were not the sole determinants of infant responding. However, the association between strangers’ and infants’ positive affect noted at 18 months was no longer detected, suggesting that the strangers’ positive affect shown towards the 18-month-olds was probably partially governed by the infant’s typical response to strangers, or temperament.

In addition, it is clear from this study that, with development, infants elicit very different responses from adults, perhaps because they become increas- ingly active partners in interaction. However, what is interesting is that, in this investigation, the sharpest differences noted in stranger behavior were between the l&month-olds and the younger infants, yet the infant behavior assessed seemed to differ most markedly between the 6-month-olds and the older infants. This suggests that 18-month-olds may be using verbal behavior and other means of initiating social interactions, which were not assessed in this investigation, to facilitate their interactions with adult strangers. These findings highlight the importance of examining bi-directionality of effects in the interaction of infant-adult dyads.

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3 May 1990; Revised 21 May 1991 n

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