A Comparative Study of Arm-Restraint Methodology: Differential Effects of Mother and Stranger Restrainers on Infants' Distress Reactivity at 6 and 9 Months of Age

Infancy, 14(3), 306324,2009 Copyright 0 Taylor & Francis Group, LLC ISSN: 1525-0008 print I 1532-7078 online DOI: 10.1080/15250000902840011

Psychology Press TaylorhFrancir Group

A Comparative Study of Arm-Restraint Methodology: Differential Effects of Mother and Stranger Restrainers

on Infants’ Distress Reactivity at 6 and 9 Months of Age

Christin L. Porter, Blake L. Jones, Cortney A. Evans, and Clyde C. Robinson

School of Family Life Brigham Young University

This study examined both differential patterns and the stability of infants’ (N = 70) distress reactivity across mother and stranger arm-restraint conditions when infants were 6 and 9 months of age. Reactivity measures included observational variables for the rise, intensity, and duration of infant distress as well as motor activities associated with escape behaviors. Correlation analyses revealed that infant behaviors during arm restraint were modestly stable across conditions and over time; however, mean comparisons also showed that infants’ distress responses appear to be sensitive to protocol parameters (whether restrainer is mother or stranger). At 6 months of age, infants cried more during maternal restraint than with strangers and exhibited escape behaviors more frequently with mothers. Findings further indicate that infants’ distress reactivity undergoes developmental alterations from 6 to 9 months of age, with infants crying more quickly, reaching peak intensity of distress faster, and displaying more distress at 9 months compared to 6 months. These changes in infants’ reactivity were particularly accentuated during maternal compared to stranger restraint conditions at 9 months of age.

Arm restraint as a moderate frustration perturbation is often employed to study anger affect and distress reactivity in infants. During this procedure the restrainer

Correspondence should be addressed to Christin L. Porter, 2093 JFSB, School of Family Lifemeu- roscience Center, Brigham Young University, Provo, UT 84602. E-mail: [email protected]

A COMPARATIVE STUDY OF ARM-RESTRAINT METHODOLOGY 307

gently holds an infant’s arms down to her or his side until the child becomes distressed for a brief period of time, or a set time has passed, typically between 30 and 180 seconds. The arm-restraint protocol often yields data on infants’ distress response, including intensity and duration of distress, latencies (time lag) to first and peak distress, and escape behaviors (attempts by infants to free themselves from the restraint), as well as infants’ facial, vocal, and physiological responses (e.g., Bennett, Bendersky, & Lewis, 2002; Fox, 1989; Scaramella & Conger, 2003; Stifter & Jain, 1996). Data from arm restraint are then often used to make inferences regarding infants’ behavioral strategies and their individual differences in emotional reactivity and regulation (e.g., Fox, 1989).

Past research implementing the arm-restraint procedure has varied with respect to who plays the part of the restrainer. For example, some studies have utilized strangers as restrainers (e.g., Bennett et al., 2002; Camras, Oster, Campos, & Miyake, 1992; Kochanska & Coy, 2002; Stifter & Spinrad, 2002), whereas other studies have utilized mothers (e.g., Braungart-Rieker & Stifter, 1996; Fox, 1989; Scaramella & Conger, 2003; Stifter & Fox, 1990; Stifter & Jain, 1996). Although largely unexplored in the literature, it seems likely that infants will show differential patterns of reactivity when the restrainer is either their mother or a stranger, particularly if the procedure is conducted during times of significant infant developmental transitions, such as the onset of stranger anxiety (Gaensbauer, Emde, & Campos, 1976; Spitz, 1950). If infants do respond differentially depending on who is restraining, this might suggest that additional care must be taken when making inferences regarding infants’ individual traits relating to anger affect and distress reactivity. Because it is unclear whether infants respond differently to stranger or mothers during arm restraint, this study was designed to examine similarities and differences when infants are 6 and 9 months of age in the rise, intensity, and duration of infants’ distress reactivity as well as escape behaviors during mother versus stranger arm-restraint conditions.

Watson (1 925) was among the first to introduce arm restraint as a protocol to assess infants’ emotional lability. Watson’s early research demonstrated that restraining infants’ movement elicited a constellation of reactivity behaviors including increased motor activity (escape attempts), negative vocalizations, and emotional distress (see also Sherman & Sherman, 1925). Anger and frustration are often associated with the blockage of activity toward an expected goal (Alessandri, Sullivan, & Lewis, 1990; Lewis & Ramsay, 2005; Stein & Jewett, 1986). Because infants by 4 to 5 months of age are gaining greater control over their limbs, it was thought that they would become distressed when their arm movements were invol- untarily restricted (Stifter & Spinrad, 2002; Thelen, Corbetta, & Spencer, 1996). Not surprisingly, most researchers who have coded facial affect during arm restraint have observed anger and distress responses (Bennett et al., 2002; Provost & Gouin-DCcarie, 1979). Although not as prevalent, other studies have shown that infants’ facial responses display a range of emotions during arm restraint, including

308 PORTER ET AL.

surprise, fear, enjoyment, and pouting (e.g., Bennett et al., 2002; Camras et al., 1992). To date, several studies confirm that infants commonly react with emotional distress when placed under mild arm-restraint conditions when the restrainers are mothers or strangers (e.g., Alessandri et al., 1990; Braungart-Rieker & Stifter, 1996; Emde, Robinson, Corley, Nikkari, & Zahn-Waxler, 2001; Fish, Stifter, & Belsky, 1991; Stenberg, Campos, & Emde, 1983; Stifter & Fox, 1990). However, no study to date has examined whether the nature of infants’ernotional distress differs when mothers or strangers act as restrainers.

Although the ability to exhibit anger in frustration-eliciting situations appears to be universal, infants often differ in the latency, intensity, and duration of their responses (Fish et al., 1991; Rothbart & Derrybeny, 1981). Most research (e.g., Rothbart & Denyberry, 1981; Stifter & Jain, 1996) suggests that these behavioral variances in the rise, duration, and intensity of behavioral responses reflect individual differences in infants’ reactivity. However, given differing methodological implementations of the arm-restraint protocol, it is not clear if variances in infants’ responses are due to differences in research protocols or to individual differences in temperament.

Besides mixed findings resulting from studies employing different arm-restraint protocols, another common confound in this line of research relates to vari- ations in the way researchers code, aggregate, and report outcomes associated with the use of mothers and strangers as restrainers. These methodological differences often make direct comparisons of studies using restraint conditions problematic (see, e.g., Stifter & Jain, 1996; Stifter & Spinrad, 2002). However, researchers who have used mothers as the restrainers have reported a fairly consistent pattern of reactivity, with a majority of infants typically displaying emotional distress and angry affect during restraint (e.g., Provost & Gouin-DCcarie, 1979; Stifter & Fox, 1990; Stifter & Jain, 1996). A similar pattern of findings has also been observed in studies using strangers as the restrainer, with a majority of infants typically demonstrating emotional distress (e.g., Bennett et al., 2002; Camras et al., 1992; Stifter & Spinrad, 2002). Unfortunately, given the various ways researchers report infants’ responses, it is difficult to know, beyond more global patterns, whether infants organize behaviors in unique ways to mothers in comparison to strangers. Therefore, one of the primary goals of this investigation was to undertake direct comparisons of infants’ responses during both maternal and stranger arm-restraint conditions.

Although it is difticult to directly compare unique features of infants’ responses during mother or stranger arm restraint from previous studies, researchers have employed other frustration protocols that provide insight into infants’ behavioral organization in relation to mothers and strangers. For instance, Stenberg et al. (1 983) examined infants’ reactions to a non-arm-restraint frustration protocol with both mothers and strangers. In this study, 4-month-old infants were given a teeth- ing biscuit that was then withdrawn by either their mother or a female stranger. In-


fants typically reacted negatively regardless of who took away the biscuit, but the authors reported that infants expressed more anger when mothers rather than strangers removed the object. This was particularly the case when infants experi- enced the stranger removal of the biscuit condition first, followed by the mother. However, when the order of the frustration task was reversed (e.g., mother first), a similar increase in anger expressed toward the stranger was not found. Unfortu- nately, what is not clear from this study is whether a similar pattern of responses on the part of the infant would remain at later ages.

In an earlier investigation, Campos, Emde, Gaensbauer, and Henderson (1975) compared behavioral and heart-rate responses with infants at both 5 and 9 months of age using a stranger and mother approach protocol. During this protocol, mothers and strangers followed a sequence of entries, departures, approach toward infant, and then an approach with intrusive behavior (getting close to the infant and holding out arms while talking to the infant). Campos et al. found a developmental shift in infants’ increased distressed behavior and heart-rate acceleration during the stranger condition but not in the mother condition. Moreover, during the stranger approach condition, infant crying was often accompanied by gaze avoid- ance and turning away, whereas distress in the mother condition was often accompanied by signals from the infant indicating a desire to be picked up (i.e., both arms raised toward the mother). Arguably the differential pattern of infant responses to mothers and strangers indicate a growing set of relational expectancies directed toward mothers compared to strangers (Alessandri et al., 1990). Again it is unclear from the literature whether a similar pattern of differential responses remains over time during a mild restraint condition such as arm restraint

To date, only a handful of studies have examined infants’ behaviors to arm restraint across time. For instance, Camras and colleagues (1992) examined U.S. and Japanese infants’ response to arm restraint at both 5 and 12 months of age with strangers (female experimenters) as restrainers. They found that older infants across both cultural groups demonstrated shorter latencies to negative response than younger infants. Older infants also exhibited greater emotional distress to restraint than younger infants, including more intense “cry faces” and angry affect as well as increased motor activity. In a more recent study, Stifter and Spinrad (2002) likewise examined infants’ reactivity to arm restraint with strangers at both 5 and 10 months of age. In this study they did not examine individual features of reactivity (latencies, rise, peak, or duration of distress), but instead employed a global coding system using a 3-point scale (e.g., high, moderate, no distress) to assess infants’ negative reactivity second by second. Similar to Camras et al. (1992), Stifter and Spinrad (2002) reported a significant increase in infants’ negative reactivity during arm restraint over time. Although speculative, it seems likely that this general increase in distress reactivity to strangers can be attributed to infants’ increasing frustration with the arm-restraint protocol, especially as infants continue to gain greater control over motor abilities (e.g., Thelen et al., 1996). However, it is

31 0 PORTER ET AL.

not clear from these studies whether a similar increase in distress reactivity over time would be observed during maternal restraint.

Functionalist theorists (e.g., Barrett, 1998; Bretherton, Fritz, Zahn-Waxler, & Ridgeway, 1986) imply that infant emotional responses are significant not only in communicating internal states, but also in the recruitment of others, such as care- givers, to help infants regulate their emotions. From a functionalist view it might be that infants not only have differing expectations regarding the “help” they can elicit from either their mother or a stranger, but might also employ differing strategies to evoke that help (Alessandri et al., 1990; Fogel, 2000). Therefore, when a mother does not appropriately respond to her infant’s emotional signals, the infant might react more negatively at the perceived violation than perhaps with a stranger. At the same time, infants’ response to violated expectancies will likely be moder- ated by the history of responsiveness the infant has received from his or her mother. This latter point unfortunately goes beyond the scope of this investigation.

In addition to infants’ motor development and functionalist explanations, it is also possible that observed changes to stranger arm restraint in previous studies can be accounted for, in part, by the onset of stranger wariness (e.g., Campos et al., 1975). Past research supports dramatic shifts in infants’ reactions to strangers during the latter half of the first year. For instance, Gaensbauer et al. (1976) conducted a longitudinal study examining infants’ distress to stranger approach between 4 and 12 months of age. They found a mean age of stranger anxiety occurring around 8 months, with distress tending to continue in subsequent stranger interactions at 12 months of age. Distress to stranger approach, however, was not evident at 4 and 5 months of age. Other researchers have similarly noted a pattern of increased infant wariness to strangers toward the latter half of the first year (e.g., Campos et al., 1975; Morgan, & Ricciuti, 1969; Putnam & Stifter, 2005). Thus, emerging stranger wariness could be confounding the findings that infants increased in distress reactivity in both the Carnras et al. (1992) and Stifter and Spinrad (2002) studies, as strangers implemented restraint protocols in both studies. By comparing reactions to both mothers and strangers, we hoped to further tease apart whether infant distress reactivity was linked to increasing stranger wariness or normative developmental changes in distress reactivity in general.

Based on previous literature, we anticipated that by 6 months of age, infants would display distress reactivity during both mother and stranger arm-restraint conditions (Stifter & Jain, 1996; Stifter & Spinrad, 2002). However, what is not clear from the literature is whether infants would respond with greater reactivity to their mother or to a stranger. For example, Gaensbauer et al. (1 976) examined infants’ distress to mother versus strangers in nonrestraint frustration situations and found fewer differential responses in infants before 4 months of age. On the other hand, Stenberg et al. (1983) found that 4-month-old infants became more distressed during maternal rather than stranger-induced frustration conditions. From an individual differences perspective (e.g., Rothbart & Derrybeny, 1981), one

A COMPARATIVE STUDY OF ARM-RESTRAINT METHODOLOGY 31 1

might also expect to find similarities (rank-order stability) in infants’ distress reactivity across conditions and over time. In spite of apparent discrepancies in the literature and given previous findings, we suspected that infants at 6 months of age would show similar individual distress response patterns across mother and stranger arm-restraint conditions. However, we suspected there would likely be an increase in the intensity of infants’ responses during the mother arm-restraint condition due to violated expectancies extending out of mother-infant relational histories.

Additionally, based on past research employing stranger arm restraint over the latter half of the first year, we expected to see an increase in the rise, intensity, and duration of infants’ distress reactivity between 6 and 9 months of age (Camras et al., 1992; Stifter & Spinrad, 2002). Unfortunately, findings in the literature do not facilitate a clear prediction as to whether infants will respond more intensely to strangers or to their mothers during arm-restraint conditions at 9 months of age. Campos et al.’s (1975) earlier work does suggest that older infants become more distressed during a stranger approach condition compared to mothers. Whether a similar pattern translates during a mild arm-restraint procedure is not currently ob- vious from the literature. From a stranger wariness theoretical perspective (Spitz, 1950, 1965), we would predict that as infants’ wariness of strangers increases, infants would show greater distress reactivity during stranger compared to mother arm-restraint conditions. On the other hand, with increasing relational expectancies in the mother-infant dyad (Fogel, 2000) it is also possible that infants might become even more distressed by perceived violation of those expectancies (Alessandri et al., 1990) when mothers act as the restrainers compared to strangers. Thus, this study was designed, in part, to examine these two competing hypotheses.

METHOD

Participants

The overall sample consisted of 101 mothers and their firstborn infants (53 girls). Participants were recruited from a Mountain West semiurban community from lo- cal birth announcements, pediatric practices, and by advertising. Infants were healthy and carried to full term (average birth weight M = 7.26 lb, range = 5.04-9.13 Ib) with no major pregnancy, birth, or perinatal complications. Mothers (M age = 25.22 years, SD = 3.80) were predominately White (94% White, 5% His- panic, 1% Asian), well educated (M = 14.45 years of education, SD = 1.79) and from intact marriages (99.2%) with an average length of marriage at 36.57 months (SD = 21.38). Thirty mothers indicated they were employed outside of the home and 62 mothers indicated that they did not work outside of the home. Nine mothers did not respond to this question. Modal family income was $29,000 to $39,000 per

31 2 PORTER ET AL.

year (range = less than $5,000 to more than $100,OOO). The sample included a high percentage of couples (43%) with at least one spouse in college. Family income was consistent, however, with average levels based on county comparisons from public tax records.

Ninety-five 6-month-old infants (50 girls) completed the maternal arm-restraint protocol (4 did not adequately settle prior to beginning the second protocol, and data were lost for 2 infants due to equipment failure). An additional eighty-five 6-month-old infants (41 girls) completed the stranger arm-restraint protocol (10 infants were not able to adequately settle, 4 infants were excluded when mothers requested that their infant not complete the second protocol, and data from another 2 infants were lost due to equipment failure). At 9 months of age, 83 of the same infants (44 girls) completed the maternal arm-restraint protocol (10 infants were lost to study attrition, 4 did not adequately settle prior to the second protocol, and 4 were lost due to equipment failure). Another 80 of the previous infants (41 girls) completed the stranger arm-restraint protocol at 9 months of age (3 additional infants did not adequately settle prior to beginning the protocol). Mean comparisons between the final sample that included infants who had complete data for each arm-restraint episode at both 6- and 9-month assessments (n = 70) and the excluded sample (n = 3 1) did not demonstrate significant differences in demographic characteristics or on any of the available reactivity measures between these groups.

Procedures

This study employed a within-subjects design with the same infants observed in differing arm-restraint conditions over time. At approximately 6 months of age (M = 195.53 days, SD = 18.28 days, range = 164-25 1 days) and 9 months of age (M = 275.41 days, SD = 9.13 days, range = 253-300 days) infants and their mothers were invited to attend a 1-hr laboratory session as part of an ongoing longitudinal study. Infants were placed in a high chair and mothers and a female research assis- tant, serving as the stranger, were instructed to gently hold the infants’ arms to their side while maintaining a neutral facial expression and refraining from verbal interaction for 90 sec. The high chair was positioned approximately 45 cm away from and angled toward a one-way mirror through which researchers were able to video- tape the infant for later coding. If the infant cried hard for more than 20 sec the restrainers were signaled to release the arms. Arm-restraint episodes did not differ in length of time between mothers and strangers at either assessment point, but did differ across time, with restraint episodes lasting longer at 6 months of age than at 9 months of age, F( 1,69) = 27 .33 ,~ < .001, I-(* = .28 (see Table 1). This was primar- ily due to experimenters ending the restraint episodes earlier at 9 months of age than at 6 months of age following a period of sustained crying.

The procedure was repeated for each infant, following a brief recovery period (typically between 1 and 3 min) with either the mother or the female research assis-


TABLE 1 Mean and Standard Deviations of Infant Behavior During Mother and Stranger

Restraint at 6 and 9 Months of Age

6-Month Mother 6-Month Stranger 9-hfonIh Mother PMonth Stranger

Variobles N M SD M SD M SD M SD

Restraint Total restraint (sec) 70 77.64 18.91, 76.17 22.59, 59.94 27.93b 62.77 29.14

Latency to first fuss 70 21.37 29.72, 20.30 31.12, 7.01 15.32b 16.60 27.28,

Latency to peak cry 6ga 60.19 26.23, 49.59 33.34 31.41 24.95, 42.07 33.46b

Duration ofcrying 70 0.44 0.33, 0.32 0.31b 0.66 0.31, 0.57 0.36, Cry intensity 70 0.14 0.10, 0.12 0.11, 0.22 0.13b 0.21 0.15b Escapeattempts 70 0.21 0.09, 0.16 0.08b 0.23 0.17, 0.17 0.12b Numberofno-cry 70 5 7.14% 5 7.14% 1 1.43% 5 7.14%

or cry (sec)

intensity (sec)

infants

Note. Means in the same row that do not share subscripts differ at p < .05 on post-hoc comparisons. aN for latency to peak intensity of cry differs because 2 infants did not become distressed.

tant serving as restrainers. During the recovery period, the mother was encouraged to calm her infant in any way she deemed appropriate. If infants were not able to adequately settle, the second arm-restraint protocol was skipped. Mothers re- mained in the room with their infants during the stranger arm-restraint protocol but were seated behind the infant and out of view so the infants could not reference their mothers. The order of mother and stranger restrainers was counterbalanced so nearly equal numbers of infants had mother or stranger restrainers first at each assessment. A series of 2 (order of restraint: mother first, stranger first) x 2 (6 months of age, 9 months of age) repeated measures analyses of variance (ANOVAs) did not indicate any main effects by order of restrainers on the infant behavior variables at either infant age. Therefore, for subsequent data analyses, the order of restraint condition was collapsed.

Infants’ Reactivity Behaviors

Building on Rothbart and Denyberry’s ( I 98 I ) approach to understanding behavioral reactivity, infants’ behaviors (i.e., temporal, intensity, and duration features) were coded along dimensions of how quickly and intensely infants become distressed. Latencies to first negative vocalizations were coded in seconds from the beginning of each arm-restraint protocol. Latencies to infants’ highest level of negative vocalization (peak intensity) were also coded from the beginning of each protocol. During each 10-sec epoch, the duration of time infants cried was also recorded and then summed for a total duration of crying score (measured in

31 4 PORTER ET AL.

seconds). Because episodes differed in length of time, the cry duration variable was summed and then divided by the total time of restraint to create a cry duration mean score.

Four trained graduate student coders, unaware of each other’s ratings, sepa- rately assessed behavioral responses to arm restraint at both 6 and 9 months of age with interrater overlap on approximately 20% of all episodes. Interrater reliability for the latency and duration variables was assessed using a f 2 sec criterion that resulted in 93% interrater agreement.

The intensity of infants’ negative vocalizations was assessed with an index of behavioral reactions scored every 10 sec on a scale of 0 (no negative vocalizations), 1 (mild whimper or fuss), 2 (escalated fuss with at least one sob or cry), 3 vull continuous cry or sobbing), and 4 (hysterical crying or shrieking; see Braungart-Rieker & Stifter, 1996). The highest intensity score for each interval was recorded. Interrater reliabilities on the 10-sec interval ratings resulted in a mean kappa of .81 at 6 months and 3 4 at 9 months of age. Crying intensity scores were summed and divided by the total number of 10-sec intervals for each episode to create a proportional mean score.

In addition to temporal and intensity features of behaviors, infants were also coded during each 10-sec epoch for escape behaviors (see later). Past research has shown that escape behaviors are often coupled with infants’ negative reactivity during arm-restraint conditions (e.g., Braungart-Rieker & Stifter, 1996; Camras et al., 1992; Stifter & Braungart, 1995). Escape behaviors were coded on a 5-point scale of 0 (no escape attempts), 1 (gentle movements, mild kicking, small hand movements), 2 (repeated tugs to escape, rubbing feet together; slight arching of back, leaning forward), 3 (arching back, twisting body, or leaning forward and twisting or more forceful kicking of legs), and 4 (in the course of more intense arching, twisting, or kicking, infant actually escapes by freeing arms even though restrainer is making effort to continue to restrain the infant). Interrater reliabilities for escape behaviors resulted in a mean kappa of .77 at 6 months and .81 at 9 months of age. Escape behaviors scores were also summed and divided by the total number of 10-sec intervals for each episode to create a proportional mean score.

RESULTS

Preliminary Analyses

Preliminary analyses examined potential links between demographic variables ( e g , maternal age, family income, education, maternal employment status) and infant behavioral variables across maternal and stranger arm-restraint conditions and across age of infant. There were no significant correlations between infants’ behavioral variables and mothers’ age, family income level, and educational status.


Simple f tests revealed that mothers who were employed outside the home had infants who cried less intensely (M = .12, SD = .lo) and engaged in less intense escape behaviors (M = .17, SD = .07) during maternal restraint at 6 months of age than infants who had mothers that were not employed (M = .16, SD = .13; M = .23, SD = .OS), f = 2 . 2 5 , ~ < .05, and r = 2 . 6 4 , ~ < .01, respectively (n = 66, as 4 mothers in the final sample did not respond to the employment question). No additional differences were found between mothers’ work status and infant behavioral outcomes.

We also examined potential gender differences on the variables of interests. Simple t tests revealed that girls exhibited slightly higher escape behaviors scores than boys (M = .24, SD = .08, M = . I 8, SD = .08, respectively) t = 3.1 3, p < .O 1, during the 6-month maternal arm-restraint condition. No additional gender differences were found; therefore, all remaining analyses were collapsed across infant gender and maternal employment status.

Data analyses were organized around two strategies. The first was to compare mean differences using a within-subjects design to assess infant behavioral reactivity measures concurrently across restraint conditions (stranger, mother) and prospectively over time (6 months of age, 9 months of age). The second strategy involved correlational analyses to examine the degree of overlap and rank-order stability in infant behaviors, again across restraint conditions and infant’s age.

Cry versus no-cry infants. To examine the effectiveness of the arm-restraint protocol to evoke infants’ distress, we first examined the number of infants who became distressed during both maternal and stranger restraint conditions at each time point. Due to unequal cell sizes and the low rate of nondistress, we employed nonparametric chi-square analyses to test restraint condition effects. These analyses (see Table 1) did not indicate any significant differences in the rate of nondistress responses (i.e., infants who did not cry during restraint) across mother and stranger conditions at 6 months of age, x2 (1, n = 70) = 1.34, p = ns. At 9 months of age, only 1 infant did not cry during maternal restraint but 5 infants did not cry during stranger restraint. This low occurrence differential resulted in a significant chi-square, x 2 (1, n = 70) = 13.19, p < .01, but represents a small subset of the overall sample. An examination of the number of infants who did become distressed showed that no fewer than 93% of participants exhibited cry behaviors to restraint during each condition at both time points, suggesting that arm restraint, regardless of the restrainer, is an effective protocol for evoking at least minimal distress in infants at both 6 and 9 months of age, particularly when mothers act as elicitors at an older age.

Infants’ Age and Restraint Condition Comparisons We next examined mean differences in infants’ behaviors across restraint conditions and infants’ age using a within-subjects repeated measures multivariate anal-

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ysis of variance with the five infant behavior variables of interest (total time of restraint, latency to first negative vocalization, latency to peak intensity of cry, duration of crying, and escape attempts) serving as the dependant variables. Wilks’s lambda indicated a main effect for restraint condition (mother vs. strangers), F(6,64) = 7.48, p < .001; infants’ age, F(6,64) = 7.69, p < ,001, and Infants’ Age x Restraint Condition interaction, F(6,64) = 3 . 2 5 , ~ < .01. Each of these variables was further examined using a univariate repeated measures ANOVA.

Latencies to first negative vocalization and peak cry intensity. Univariate ANOVA for latency to first negative vocalization showed no main effect for restraint condition, F( 1,69) = 2.53, p = ns, v* = .03; however, a significant main effect for infant age was found, F( I , 69) = 10.07, p < .01, q* = .12, as was a significant Restraint Condition x Age interaction, F( 1, 69) = 4.80, p < .05, q2 = .06. Post-hoc analyses (see Figure 1) using Fisher’s least significant differences showed that latencies to first negative vocalizations decreased between 6 and 9 months of age during mother restraint, F( 1,69) = 19.59, p < .OO 1, and were shorter during maternal restraint at 9 months of age compared to stranger restraint, F( 1, 69) = 8.57, p < .01.

Analyses of the latency to peak intensity of distress likewise showed no main effect for restraint condition, F( 1,67) = 0 . 0 2 , ~ = ns, @ = .OO, but did differ significantly across infant age, F( 1,67) = 30 .77 ,~ < .001, v2 = .33, showing decreased latencies between 6 and 9 months of age. As can be seen in Table 1, a significant Re-

Latency to First Cry

30

1 25 4 .~

T

6-Month Mother 6-Month Stranger 9-Month Mother 9-Month Stranger

Figure l a

FIGURE 1 restrainers and time.

Mean latency to first negative vocalizations during arm restraint (+ SE) across


straint Condition x Age of Infant interaction was also found, F( 1,67) 1 1.7 1, p < .OOl, q 2 = .16. Post-hoc analyses revealed that infants more quickly reached a peak intensity of distress during stranger restraint at 6 months, F( 1,67) = 7.26, p < .01; however, this pattern reversed at 9 months, with infants reaching peak intensity more quickly during maternal restraint conditions, F( 1,67) = 5.39, p < .01. These analyses further revealed that infants reached their peak intensity more rapidly at 9 months of age during maternal restraint, F( 1,67) = 57.59, p < .001, but did not differ between 6 and 9 months of age in the stranger restraint condition (see Figure 2).

Cry duration and cry intensity. Additionally, cry duration showed a main effect for restraint condition, F( 1,69) = 7.8 I , p < .OO, q2 = . l 1, with infants crying more during maternal restraint. Results also revealed a main effect for infant age, F( 1,69) = 36.14, p < .001, q2 = .35, with infants crying longer at 9 months of age. The Restraint Condition x Infant Age interaction for crying duration was not significant.

A univariate ANOVA for mean intensity of cry did not show a main effect for restraint condition, F( 1,67) = 1.26, p = ns, q2 = .02, but did show a main effect for infant age, F( I , 69) = 32.61, p < .001, q 2 = .32, with cry intensity increasing during both mother and stranger restraint conditions between 6 and 9 months of age. The Restraint Condition x Age interaction for cry intensity was not significant.

Escape behaviors. Univariate analyses were also conducted on infants’ escape behaviors. A main effect for restraint condition was found, F( 1,69) = 15 .93 ,~

Latency to Peak Distress

6-Month Mother 6-Month Stranger 9-Month Mother 9-Month Stranger

Figure 1 b

FIGURE 2 ers and time.

Mean latency to peak of cry or distress during arm restraint (+ SE) across restrain-

31 8 PORTER ET AL.

< .001, qz = .19, but not for infant age or the interaction of restraint condition and age. In this case, infants exhibited escape behaviors more intensely during the mother restraint condition at both 6 and 9 months of age.

Concurrent and Across-Time Correlations During Mother and Stranger Restraint

Although mean comparisons can demonstrate potential changes and differences in infants’ behaviors across restraint conditions and infant age, they do not tell us about the degree of relatedness and the relative rank-order stability of individual behaviors within groups. As such, although groups might differ across restraint condition or across age, individuals might retain their relative rank-order within the group, demonstrating perhaps consistency in individual trait-like behaviors (Hsu & Porter, 2004). Therefore, in addition to mean comparisons, correlation analyses were conducted to ascertain the degree of overlap and stability in infants’ behaviors during the differing arm-restraint conditions and over time.

Concurrent analyses. Correlation analyses examined both concurrent and cross-age linkages between and within conditions (see Table 2). Concurrent correlations between infant behaviors during mother and stranger restraint at 6 months of age revealed modest links. Four of the five infant behavior variables during restraint were significant, with an average correlation of r = .32, however, infant escape behaviors were not significantly correlated. A similar pattern of concurrent correlations was observed at 9 months of age between stranger and mother conditions (average r = .30) with the exception that escape behaviors were now significantly correlated ( r = .36, p < .01).

Across time analyses. Correlation analyses were also conducted for behaviors during mother and stranger conditions from 6 to 9 months of age (see Table 2). Four of the five across-age correlations during the maternal restraint condition were significant, with an average correlation of r = 2 8 (see Table 2). A similar pattern of findings was also observed between 6 and 9 months of age for stranger restraint conditions (average r = .30).

DISCUSSION

Findings from this study demonstrate three important outcomes. First, infants appear to respond differentially to mothers and strangers on individual measures of distress reactivity during arm restraint at both 6 and 9 months of age. Second, patterns of response appear to undergo developmental alterations between 6 and 9 months of age. Third, despite changes in mean levels of behaviors, findings sug-


TABLE 2 Concurrent and Across-Time Correlations of Infant Behavior During

Mother and Stranger Restraint at 6 and 9 Months of Age

Variabfes 6-Month Stranger 9-Month Maternal

6-month maternal restraint

vocalization (sec)

distress (sec)

Latency to first negative .37*** .42***

Latency to peak intensity of .40*** .26**

Duration of crying .37*** .28** Cry intensity .34*** .25** Escape attempts .10 .19

9-Month Stranger

6-month stranger restraint Latency to first negative

vocalization (sec) Latency to peak intensity of

distress (sec) Duration of crying Cry intensity Escape attempts

9-month maternal restraint Latency to first negative

vocalization (sec) Latency to peak intensity of

distress (sec) Duration of crying Cry intensity Escape attempts

.24**

.26**

.26**

.27**

.19

.27**

.22*

.29**

.38***

.36***

*p<.IO. **p< .05 .***p< .Ol .

gest some stability in infants’ responses to mild frustration across restraint conditions and over time. Each of these outcomes is discussed next.

Consistent with expectations, we observed that arm restraint administered at 6 and 9 months of age by both mothers and strangers elicited a distress response in the vast majority of infants, regardless of who elicited the distress. This finding co- incides with past work demonstrating that infants commonly respond to mild frustration and goal blockage with angry or distressed affect (e.g., Alessandri et al., 1990; Hsu & Porter, 2004; Lewis & Ramsay, 2005; Stein & Jewett, 1986) and do so whether mothers or strangers are involved in inducing the frustration (e.g., Sten- berg et al., 1983). Although most infants became distressed, we note that the behavioral organization of distress varied to some degree across restraint conditions (i.e., mother vs. stranger as restrainer) as well as over time.

320 PORTER ET AL.

Infant Behavior During Mother Versus Stranger Restraint Conditions

Mean comparisons of mother and stranger restrainers at 6 months of age revealed no differences in infants’ latency to first negative vocalization or the amount of time to reach peak of distress. Infants did, however, differ in their duration or crying and escape behaviors, crying more and exhibiting more vigorous escape behaviors during maternal restraint conditions. Although there were some slight vari- ations in infants’ behavioral organization, concurrent correlational analyses at 6 months of age also revealed that latency to distress variables was moderately related across conditions. This suggests some stability in infants’ initial response to arm restraint as well as stability in the amount of time it takes them to become distressed (Rothbart & Derryberry, 1981).

As anticipated, by 9 months of age, infants were found to have shorter latencies to both initial distress and rise to peak distress compared to 6 months of age. These findings appear again to be consistent with past studies that likewise have shown a decreasing latency to distress and greater distress response during arm restraint toward the latter half of the first year (e.g., Camras et al., 1992; Stifter & Spinrad, 2002). Although somewhat speculative, it is likely that this decreasing latency for distress reactivity might be related to infants’ emerging sense of intentionality, particularly as related to goal-directed behavior (e.g., Flavell, 1999). It could be that by 9 months of age infants more quickly grasp the nature of the perturbation and the intended action of the restrainer, which in turn might disrupt the normal course of reciprocal interactions and lead to even greater distress (e.g., Tronick & Gianino, 1986). Some support for this idea is found in the current findings that infants not only had shorter latencies to distress and peak distress intensity but also cried more intensely at 9 months than at 6 months of age. Additionally, arm re- straints were ended approximately 14 to 16 sec earlier at 9 months than at 6 months of age because of apparent increase in infants’ distress responses. This is perhaps an additional marker of increased intensity of distress in these older infants. Alter- natively, although not directly observed, it could be that as infants mature they increase their capacity to produce self-generated movement (Thelen et al., 1996) which might also make restraint conditions at 9 months of age even more frustrating, further adding to the quicker rise time of distress.

To better understand the nature of these changes in distress reactivity we further examined similarities and differences in infants’ behaviors under conditions when mothers and strangers acted as restrainers. Findings demonstrated that by 9 months of age, mothers evoked a faster distress response from infants than strangers both in terms of shorter latencies to first negative vocalization and peak intensity of distress. Although again not directly observed in this study, it seems likely that this emerging pattern of distress response with mothers could be connected to matur- ing relational expectancies on the part of infants and the resulting violation of these


expectancies that are built within the historical relationship of mother-infant dyads (see Fogel, 2000; Hsu & Fogel, 2003; Kochanska, 2001). Additional study is needed to fully explicate this notion and would benefit from research designs that capture relational features of mother-infant dyads in addition to infants’ differential responses to mothers and strangers. Despite this limitation, support for a violated expectations explanation on the part of developing infants is garnered by past research that has demonstrated the efficacy of the still-face paradigm with infants to elicit distress responses when perturbation of dyadic interactions occurs (e.g., Adamson & Frick, 2003; Lamb, Momson, & Malkin, 1987). For instance, in Ad- amson and Frick’s (2003) review, they argued that the still face is effective in prompting distress in infants “because the procedure violates the rules that govern the mutual regulation of social interactions” (p. 462). A similar argument could be made with respect to arm-restraint protocols, especially when arm restraint is coupled with presentation of a neutral or “still” face during restraint by both mothers and strangers, as in the case of this investigation. However, our finding that infants responded more quickly and with more intense distress features at 9 months of age with mothers rather than strangers would suggest that the “rules that govern mutual regulation” perhaps operate in the context of specific relationships that are not ger- mane to human interactions in general.

Additional infant behavioral outcomes in this study might indirectly support a mutual regulation supposition; specifically, infants were found to not only cry longer during maternal arm restraint, but also increased the intensity of their escape behaviors during maternal restraint compared to stranger restraint at both 6 and 9 months of age. Again, these cry and escape behaviors might indicate that infants perceive the maternal arm restraint as a greater violation of expectancies given the historical nature of their relationship (Hsu & Fogel, 2003). From a functionalist perspective, it could be argued that infants expect greater help to remediate distress from their mothers than from strangers and thus increase their rate of crying in an attempt to gather that support. However, when that support is not forthcoming, infants perhaps are more likely to increase their attempts to escape from the restraint condition to help remediate their own distress.

Stability of Infant Behaviors Across Conditions and Time

We finally considered outcomes regarding the rank-order stability of infants’ behaviors across restraint conditions and over time. Correlation analyses helped us to understand that even though there might be differential patterns of responses in infants’ behaviors, there was also modest stability in individual behaviors as well. These findings appear consistent with past research that has shown modest to moderate amounts of overlap in observed and reported individual behaviors across experimental situations and with increasing age (e.g., Goldsmith & Rothbart, 1991; Hsu & Porter, 2004; Hubert, Wachs, Peters-Martin, & Gandour, 1982; Seifer,

322 PORTER ET AL.

Sameroff, Barrett, & Krafchuk, 1994; Slabach, Morrow, & Wachs, 1991). To- gether these findings suggest that even though several infant behaviors are sensitive to protocol parameters, there exists some behavioral variance across conditions and over time that can be attributed to individual differences in infants’ temperament.

Together these findings suggest that care is needed in designing and implementing mild perturbation techniques to assess infants’ response to frustration. It could be that infants under differing conditions not only demonstrate individual characteristics with regard to proneness-to-distress tendencies (e.g., Rothbart & Derry- berry, 198 I ) , but might organize their behaviors around relational expectancies given who elicits the distress response. During mild restraint, it appears that infants might respond faster and with greater distress to violation of social expectancies with a primary caregiver rather than with a stranger (e.g.. Fogel, 2000). This might suggest that researchers attempting to achieve more rapid emotional lability in infants, especially those working with older infants, could benefit by utilizing mothers as opposed to strangers during arm restraint.

Although not examined in this study, it could also be that infants are more likely to call on relationship expectancies to engage self-regulatory process in the presence of their primary caregiver but have greater difficulty accessing similar self-regulating strategies with a stranger. Additional research is needed to more fully explicate this possibility and to help us better understand the specific strategies infants engage to soothe themselves under differing perturbation conditions. In addition, it would also be important in future research to examine the specific emotional content of infants’ responses during mother and stranger perturbation tasks to further tease apart the nature of infants’ distress reactivity. It could be that as infants get older they are more likely to engage a fear and anxiety system in the presence of strangers and an anger and frustration system with their mothers. Such research would allow for a fuller understanding of the differential patterns of responses observed in this investigation and would help further an understanding of the effectiveness of the arm-restraint protocol to elicit distress reactivity in infants.

ACKNOWLEDGMENTS

This project was supported by generous funding from the Family Studies Center, the Camilla Eyring Kimball Chair, and the Mary Lou Fulton Young Scholar Chair at Brigham Young University awarded to Christin L. Porter. We would like to thank Rebecca L. Farmer, Staci S. Ohmni, Adrienne Earnest Porter, Taralyn Trost Parker, and Elizabeth C. Haynie Brown for their help in data collection, coding, and library research. Additional thanks go to the mothers and infants who partici- pated in this project. Appreciation is also expressed to Dr. Celia A. Brownell for her encouraging and careful editorial oversight of this article and to the three anon-


ymous reviewers who likewise helped to strengthen this article by their insightful comments and feedback.

REFERENCES

Adamson, L. B., & Frick, J. E. (2003). The still face: A history of a shared experimental paradigm. In-

Alessandri, S. M., Sullivan, M. W., & Lewis, M. (1990). Violations of expectancy, loss of control, and anger expressions in young infants. Developmental Psychology, 26, 745-75 1.

Barrett, K. C. (1998). A functionalist perspective on the development of emotions. In M. S. Mascolo & S. Giftin (Eds.), What devefops in emotional development? (pp. 109-134). New York: Springer.

Bennett, D. S., Bendersky, M., & Lewis, M. (2002). Facial expressivity at 4 months: A context by expression analysis. Infancy, 3, 97-1 13.

Braungart-Rieker, J. M., & Stifter, C. (1996). Infants’ responses to frustrating situations: Continuity and change in reactivity and regulation. Child Development, 67, 1767-1779.

Bretherton, I., Fritz, J., Zahn-Waxler, C., & Ridgeway, D. (1986). Learning to talk about emotions: A functionalist perspective. Child Devefopment, 57, 529-548.

Campos, J., Emde, R., Gaensbauer, T., & Henderson, C. (1975). Cardiac and behavioral interrelation- ships in the reactions of infants to strangers. Developmental Psychology, 11, 589-601.

Camras, L. A., Oster, H., Campos, J. J., & Miyake, K. (1992). Japanese and American infants’ responses to arm restraint. Developmental Psychology, 28. 578-583.

Emde, R. N., Robinson, J. L., Corley, R. P., Nikkari, D., & Zahn-Waxler, C. (2001). Reactions to restraint and anger-related expressions during the second year. In R. N. Emde & J. K. Hewitt (Eds.), Infancy to early childhood: Genetic and environmental influences on developmental change (pp. 127-140). London: Oxford University Press.

Fish, M., Stifter, C. A., & Belsky, J. (1991). Conditions of continuity and discontinuity in infant negative emotionality: Newborn to five months. Child Developmenr, 62, 1525-1537.

Flavell, J. H. (1999). Cognitive development: Children’s knowledge about the mind. Annual Review of Psychology, 50, 2 1 4 5 .

Fogel, A. (2000). Beyond individuals: A relational-historical approach to theory and research on communication. In M. L. Genta (Ed.), Mother-infant communication (pp. 123-161). Rome: Caroci.

Fox, N. (1989). Psychophysiological correlates of emotional reactivity during the first years of life. De- velopmental Psychology, 25, 364-372.

Gaensbauer, T. J., Emde, R. N., & Campos, J. J. (1976). Stranger distress: Confirmation of a developmental shift in a longitudinal sample. Perceptual & Motor Skills, 43, 99-106.

Goldsmith, H., & Rothbart, M. K. (1991). Contemporary instruments for assessing early temperament by questionnaire and in the laboratory. In J. Strelau & A. Angleitner (Eds.), Exploration of tempem- rnent (pp. 249-272). New York: Plenum.

Hsu, H., & Fogel, A. (2003). Stability and transitions in mother-infant face-to-face communication during the first 6 months: A microhistorical approach. Developmental Psychorogy, 39,

Hsu, H., & Porter, C. L. (2004). Young infants’behavioral reactivity to mild p e w t i o n : Developmental

Hubert, N. C., Wachs, T. D., Peters-Martin, P., & Gandour, M. J. (1982). The study of early tempera-

Kochanska, G. (2001). Emotional development in children with different attachment histories: The first

fancy, 4, 451473.

I06 1 - 1082.

continuity, stability, and organization. Infancy, 6, 95-1 20.

ment: Measurement and conceptual issues. Child Development, 53, 57 1-600.

three years. Child Development, 72, 474-490.

324 PORTER ET AL.

Kochanska, G., & Coy, K. C. (2002). Child emotionality and maternal responsiveness as predictors of reunion behaviors in the strange situation: Links mediated and unmediated by separation distress. Child Development, 73, 228-240.

Lamb, M., Morrison, D. C., & Malkin, C. M. (1987). The development of infant social expectations in face-to-face interaction: A longitudinal study. Merrill- Palmer Quarterly, 33, 24 1-254.

Lewis, M., & Ramsay, D. (2005). Infant emotional and cortisol responses to goal blockage. Child De- velopment, 76, 5 18-530.

Morgan, G., & Ricciuti, H. (1969). Infants’ responses to strangers during the first year. In B. Foss (Ed.), Determinants ofinfant behavior (Vol. 4, pp. 253-272). New York: Wiley.

Provost, M. A,, & Gouin-DCcarie, T. (1979). Heart rate reactivity of 9- and 12-month old infants showing specific emotions in natural settings. International Journal of Behaviorul Development, ,?,

Putnam, S. P., & Stifter, C. A. (2005). Behavioral approach-inhibition in toddlers: Prediction from infancy, positive and negative affective components, and relations with behavior problems. Child De- velopment, 76, 2 12-226.

Rothbart, M. K., & Denybeny, D. (1981). Development of individual differences in temperament. In M. K. Lamb & A. L. Brown (Eds.), Advances in developmental psychology (Vol. I. pp. 37-86). Hillsdale, NJ: Lawrence Erlbaum Associates, Inc.

Scaramella, L. V., &Conger, R. D. (2003). Intergenerational continuity of hostile parenting and its con- sequences: The moderating influence of children’s negative emotional reactivity. Social Develop- ment, 12, 4 2 W 3 9 .

Seifer, R., Sameroff, A. J., Barrett, L. C.. & Krafchuk, E. (1994). Infant temperament measured by mul- tiple observations and mother report. Child Development, 65, 1478-1 490.

Sherman, M., & Sherman 1. C. (1925). Senson-motor responses in infants. Journal of Comparative P.yychology, 5, 53-68.

Slabach, E., Morrow, J., & Wachs, T. D. (199 I) . Questionnaire measurement of infant and child temperament. In J. Strealu & A. Angleitner (Eds.), Explorarions in temperament (pp. 205-233). New York: Plenum.

Spitz, R. A. (1950). Anxiety in infancy: A study of its manifestations in the first year of life. Interna- tional Journal of Psycho-Analysis, 31, 138-143.

Spitz, R. A. (1965). Thefirst year .flife. New York: International Universities Press. Stein, N. L.. & Jewett, J. J. (1986). A conceptual analysis of the meaning of negative emotions: Implica-

tions for a theory of development. In C. E. Izard & P. B. Read (Eds.), Measuring emotions in infants and children (Vol. 2, pp. 238-267). Cambridge: Cambridge University Press.

Stenberg, C. R., Campos, J. J., & Emde, R. N. (1983). The facial expression of anger in seven- month-old infants. Child Development, 54, 178-184.

Stifter, C. A., & Braungart, J. M. (1995). The regulation of negative reactivity in infancy: Function and development. Developmental Psychology, 31,448455.

Stifter, C. A., &Fox, N. A. (1990). Infant reactivity: Physiological correlates of newborn and 5-month temperament. Developmental Psychology, 26, 582-588.

Stifter, C. A.. & Jain, A. (1996). Psychophysiological correlates of infant temperament: Stability of behavior and autonomic patterning from 5 to 18 months. Developmental Psychobiology, 2Y, 379-391.

Stifter, C. A., & Spinrad, T. L. (2002). The effect of excessive crying on the development of emotional regulation. Infancy, 3. 133-152.

‘Ihelen, E., Corbetla, D., & Spencer, J. F? (1996). Development of reaching during the first year: Role of movement speed. Journul of Experimentul Psychology: Hwnan Perception and P e r f o m r e , 22, 1059-1076.

Tronick, E. 2.. & Gianino. A. F. (1986). The transmission of maternal disturbance to the infant. In E. Z. Tronick & T. Field (Eds.), Maternal depression and infant disturbance (pp. 5-1 1 ). New York: Wiley.

Watson, J. B. ( I 925). Experimental studies on the growth of emotions. Pediarric Seminars, 32, 328-348.

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Documents

A Comparative Study of Arm-Restraint Methodology: Differential Effects of Mother and Stranger Restrainers on Infants' Distress Reactivity at 6 and 9 Months of Age