Age and walking conditions differently affect domains of gait

IntroductionAnalysing gait in controlled conditions that resemble daily life walking could overcome the limitations associated with gait analysis in uncontrolled real-world conditions. Such analyses could potentially aid the identification of a walking condition that magnifies age-differences in gait. Therefore, the aim of the current study was to determine the effects of age and walking conditions on gait performance.MethodsTrunk accelerations of young (n = 27, age: 21.6) and older adults (n = 26, age: 68.9) were recorded for 3 min in four conditions: walking up and down a university hallway on a track of 10 m; walking on a specified path, including turns, in a university hallway; walking outside on a specified path on a pavement including turns; and walking on a treadmill. Factor analysis was used to reduce 27 computed gait measures to five independent gait domains. A multivariate analysis of variance was used to examine the effects of age and walking condition on these gait domains.ResultsFactor analysis yielded 5 gait domains: variability, pace, stability, time & frequency, complexity, explaining 64% of the variance in 27 gait outcomes. Walking conditions affected all gait domains (p < 0.01) but age only affected the time & frequency domain (p < 0.05). Age and walking conditions differently affected the domains variability, stability, time & frequency. The largest age-differences occurred mainly during straight walking in a hallway (variability: 31% higher in older adults), or during treadmill walking (stability: 224% higher, time&frequency: 120% lower in older adults).ConclusionWalking conditions affect all domains of gait independent of age. Treadmill walking and walking on a straight path in a hallway, were the most constrained walking conditions in terms of limited possibilities to adjust step characteristics. The age by condition interaction suggests that for the gait domains variability, stability, and time & frequency, the most constrained walking conditions seem to magnify the age-differences in gait.     

Unattractive infant faces elicit negative affect from adults

We examined the relationship between infant attractiveness and adult affect by investigating whether differing levels of infant facial attractiveness elicit facial muscle movement correlated with positive and negative affect from adults (N = 87) using electromyography. Unattractive infant faces evoked significantly more corrugator supercilii and levator labii superioris movement (physiological correlates of negative affect) than attractive infant faces. These results suggest that unattractive infants may be at risk for negative affective responses from adults, though the relationship between those responses and caregiving behavior remains elusive.     

The role of crawling and walking experience in infant spatial memory

This research explored infants' use of place learning and cue learning in a locomotor task across the transition from crawling to walking. Novice and expert crawling and walking infants were observed in a novel locomotor task-finding a hidden goal location in a large space. In Experiment 1, infants were tested with distal landmarks. Infants with fewer than 6 weeks of experience, either crawling or walking, could not find the goal location. All infants with more locomotor experience were more successful. Learning did not transfer across the transition to walking. In Experiment 2, novice and expert crawlers and walkers were tested with a direct landmark. Again, novice crawlers and walkers with fewer than 6 weeks of experience could not find the goal, whereas those with more experience could. Taken together, these findings suggest that infants' spatial learning is inextricably linked to mode of locomotion.     

Mothers' perceptions of infant affect in a croatian sample: The IFEEL pictures assessment

Recent work demonstrates systematic variability in mothers' perceptions of infant affects in adolescent, depressed, abusive, and preterm mothers (Emde, Osofsky,&Butterfield, 1993). This Croatian study, completed before the war in the former Yugoslavia, reports cultural differences and similarities in mothers' interpretation of infant affect in 103 mothers of healthy, full-term Croatian infants when compared to an American sample. The IFEEL Pictures (IFP) were administered to assess mothers' perception and interpretation of infants' facial expressions. Comparisons of the IFP scores for Croatian and American mothers revealed significant differences in 3 of 12 affect categories, controlling for education. Croatian mothers with different educational backgrounds showed significant differences in their perceptions of infants' affects. Differences between American mothers and Croatian educated mothers were less marked than those between Croatian high-educated and low-educated mothers. Our work suggests that there are cultural differences and similarities in affect interpretation between Croatian and American mothers. If this finding holds, it suggests that studies are needed of the effects if any, on mother-child interaction and child-rearing patterns, and possible differences in cross-cultural affect development.     

Maternal postnatal psychiatric symptoms and infant temperament affect early mother-infant bonding

Postnatal mother-infant bonding refers to the early emotional bond between mothers and infants. Although some factors, such as maternal mental health, especially postnatal depression, have been considered in relation to mother-infant bonding, few studies have investigated the role of infant temperament traits in early bonding. In this study, the effects of maternal postnatal depressive and anxiety symptoms and infant temperament traits on mother-infant bonding were examined using both mother and father reports of infant temperament. Data for this study came from the first phase of the FinnBrain Birth Cohort Study (n = 102, father reports n = 62). After controlling for maternal symptoms of depression and anxiety, mother-reported infant positive emotionality, measured by infant smiling was related to better mother-infant bonding. In contrast, infant negative emotionality, measured by infant distress to limitations was related to lower quality of bonding. In regards to father-report infant temperament, only infant distress to limitations (i.e., frustration/anger) was associated with lower quality of mother-infant bonding. These findings underline the importance of infant temperament as one factor contributing to early parent-infant relationships, and counseling parents in understanding and caring for infants with different temperament traits.     

Head flexion and different walking speeds do not affect gait stability in older females

Head flexion is destabilizing in older individuals during quiet stance, yet the effect head flexion has on gait is not known. The study examined whether head flexion and gait parameters were altered when walking freely and fixed to a visual target, at different walking speeds. 15 young (23 ± 4 years) and 16 older (76 ± 6 years) healthy females walked at three different walking speeds (slow, comfortable, and fast) under two visual conditions (natural and fixed [focusing on a visual target set at eye level]). Head flexion was assessed using 2D video analysis, whilst gait parameters (step length, double support time, step time, and gait stability ratio) were recorded during a 9 m flat walkway. A mixed design ANOVA was performed for each variable, with age as the between-subject factor and, visual condition and walking speed as within-subject factors. When walking freely, older displayed a greater need for head flexion between walking speeds (P < 0.05) when compared to young. Walking under fixed condition reduced head flexion at all walking speeds in the older (P < 0.05), but had no effect on the young (P > 0.05). Walking at different speeds showed no difference in head flexion when walking under either visual condition and had no effect on gait stability for both groups. Despite older displaying differences in head flexion between visual conditions, there was no effect on gait parameters. Walking speed presented trivial difference in head flexion in older females, whilst overall gait stability was unaffected by different walking speeds.     

Parent mind-mindedness,sensitivity, and infant affect: Implications for attachment with mothers and fathers

Previous research examining links between parenting and attachment has focused on behavioral aspects of parenting such as sensitivity. However, by assessing how parents reflect on infants’ mental states (mind-mindedness) we gain a broader understanding of parenting and how it impacts attachment. Mothers, fathers, and their infants (N = 135) participated in the Still Face Paradigm (SFP) at 3-, 5-, and 7- months of age, and the Strange Situation with mothers at 12 months and fathers at 14 months. Parent sensitivity and infant affect were coded from the SFP and all videos were transcribed and later coded for parents’ use of appropriate and non-attuned mind-mindedness toward their infants. Attachment with each parent was coded from the Strange Situation. Mixed effects models examined trajectories of parents’ mind-mindedness in relation to parent sensitivity and infant affect across attachment groups. Significant differences between parent gender and attachment category were detected. Specifically, parents who were less sensitive were also less mind-minded toward insecure-avoidant infants; parents used more non-attuned mind-mindedness when infants had higher negative affect. Findings suggest that, in addition to parent sensitivity, parents’ use of appropriate and non-attuned mind-mindedness during a parent-infant interaction provides insight into the developing attachment relationship for mothers and fathers.     

The association between prenatal exposure to cigarettes and infant and maternal negative affect

This study examined the association between prenatal exposure to cigarettes and infant and maternal negative affect. Participants were 115 mother-infant dyads (69 prenatally exposed to cigarettes and 46 nonexposed). Infant and maternal negative affect were both assessed during the neonatal period (2-4 weeks of age) and again at 7 months of infant age. Results indicated that only prenatal exposure to cigarettes predicted infant negative affect. Infants who were prenatally exposed to more cigarettes had higher levels of negative affect at both time points. Furthermore, regression analyses indicated that both infant and maternal negative affect during the neonatal period predicted maternal negative affect at 7 months of age. These results highlight the importance of considering the reciprocal relationship between infant and maternal behavior when examining developmental outcomes among infants prenatally exposed to cigarettes.     

Reaching while walking: Reaching distance costs more than walking distance

Surprisingly little is known about how people plan and control everyday physical actions, such as walking along and picking up objects. In order to explore this topic, we conducted an experiment in which university students were asked to pick up a common object (a child’s beach bucket) that stood on a table several meters from the participant’s start position. The bucket stood either on the left side, in the middle, or on the right side of the table and, depending on instructions, was to be carried to a farther target whose horizontal position was also varied. The questions were which side of the table the participant would walk along when picking up the bucket and which hand the participant would use to pick up and carry the bucket. Participants, most of whom were righthanded, preferred to walk along the left side of the table and to pick up the bucket with the right hand, although they departed from that preference when the reaching distance across the table was uncomfortable or if the target was too far to the right. The data were well fit with a mathematical model that included a right-hand bias and an estimate of functional distance that expressed the cost of reaching over some distance as approximately twice the cost of walking over the same distance.     

The development of infant discrimination of affect in multimodal and unimodal stimulation: The role of intersensory redundancy

This research examined the developmental course of infants' ability to perceive affect in bimodal (audiovisual) and unimodal (auditory and visual) displays of a woman speaking. According to the intersensory redundancy hypothesis (L. E. Bahrick, R. Lickliter, & R. Flom, 2004), detection of amodal properties is facilitated in multimodal stimulation and attenuated in unimodal stimulation. Later in development, however, attention becomes more flexible, and amodal properties can be perceived in both multimodal and unimodal stimulation. The authors tested these predictions by assessing 3-, 4-, 5-, and 7-month-olds' discrimination of affect. Results demonstrated that in bimodal stimulation, discrimination of affect emerged by 4 months and remained stable across age. However, in unimodal stimulation, detection of affect emerged gradually, with sensitivity to auditory stimulation emerging at 5 months and visual stimulation at 7 months. Further temporal synchrony between faces and voices was necessary for younger infants' discrimination of affect. Across development, infants first perceive affect in multimodal stimulation through detecting amodal properties, and later their perception of affect is extended to unimodal auditory and visual stimulation. Implications for social development, including joint attention and social referencing, are considered.     

The disturbed caregiving system: Relations among childhood trauma,maternal caregiving,and infant affect and attachment

The interrelations among maternal childhood experiences of physical or sexual abuse, adult trauma-related symptoms, adult caregiving behavior, and infant affect and attachment were investigated among 45 low-income mothers and their 18-month-old infants. A history of physical abuse was associated with increased hostile-intrusive behavior toward the infant, increased infant negative affect, and a decreased tendency to report trauma-related symptoms. A history of sexual abuse was associated with decreased involvement with the infant, more restricted maternal affect, and more active reporting of trauma-related symptoms. Infants of mothers who had experienced childhood violence or abuse were not more likely to display insecure attachment strategies than infants of mothers who had not experienced trauma. However, the form of insecure behavior was significantly different. Insecure infants of violence-exposed mothers displayed predominantly disorganized strategies, whereas insecure infants of mothers with benign childhoods or neglect only displayed predominantly avoidant strategies. Results are discussed in relation to Main and Hesse's (1990) concept of frightened or frightening behavior and to current literature on psychological sequelae of trauma.     

Associations between mother-infant bed-sharing practices and infant affect and behavior during the still-face paradigm

Parents in the United States increasingly report bed-sharing with their infants (i.e., sleeping on a shared sleep surface), but the relationship between bed-sharing and child socioemotional outcomes are not well understood. The current study examines the links between mother-infant bed-sharing at 3 months and infant affect and behavior during a dyadic challenge task at 6 months. Further, we examine nighttime mother-infant contact at 3 months as a possible mechanism that may mediate linkages between bed-sharing and infant outcomes. Using observational data from a sample of 63 mother-infant dyads, we found that infants who bed-shared for any proportion of the observation period at 3 months displayed significantly more self-regulatory behaviors during the still-face episode of the Still-Face Paradigm (SFP) at 6 months, compared to non-bed-sharing infants. Also, infants of mothers who bed-shared for the entire observation period displayed significantly less negativity during the reunion episode than non-bed-sharing infants. There was no evidence that the relations between mother-infant bed-sharing practices and infant affect and behavior during the SFP were mediated through nighttime mother-infant contact. Results suggest that infant regulation at 6 months postpartum may vary based on early nighttime experiences, with bed-sharing potentially promoting more positive and well-regulated behavior during dyadic interaction.     

Maternal positive responses to a distressed infant simulator predict subsequent negative affect in infants

Existing evidence indicates that maternal responses to infant distress, specifically more sensitive and less inconsistent/rejecting responses, are associated with lower infant negative affect (NA). However, due to ethical and methodological constraints, most existing studies do not employ methods that guarantee each mother will be observed responding to infant distress. To address such limitations, in the current study, a distressed infant simulator (SIM), programmed to be inconsolable, was employed to ensure that mothers (N = 150; 4 months postpartum) were observed responding to infant distress. Subsequently, maternal report of infant NA and an early aspect of regulatory capacity, sootheability, were collected at eight-months postpartum, and observational assessments of infant fear and frustration, fine-grained aspects of NA, were collected at 12-months of age. After controlling for infant sex, the proportion of time mothers spent using soothing touch during the SIM task was related to less overall maternal reported NA and sadness at eight-months postpartum. Similarly, greater use of touch was associated with less fear reactivity, and greater maternal use of vocalizations was related to lower infant frustration, at 12-months postpartum. Specific maternal soothing behaviors were not related to infant soothability at 8 months postpartum. Total time spent interacting with the SIM was not related to infant temperament, suggesting that type of soothing, not quantity of interactions with distressed infants, is important for reducing infant NA. The implications of these findings and important future directions are discussed.     

Mutual regulation between infant facial affect and maternal touch in depressed and nondepressed dyads

The ability to regulate affect is important for later adaptive child development. In the first months of life, infants have limited resources for regulating their own affects (e.g. by gaze aversion), and for this reason they are dependent on external affect regulation from their parents. Previous research suggests that touch is an important means through which parents regulate their infants’ affects. Also, previous research has shown that post-partum depressed (PPD) mothers and nonclinical mothers differ in their touching behaviors when interacting with their infants. We examined the affect-regulating function of affectionate, caregiving and playful maternal touch in 24 PPD and 47 nonclinical mother-infant dyads when infants were four months old. In order to investigate the direction of effects and to account for repeated observations, the data were analysed using time-window sequential analysis and Generalized Estimating Equations. The results showed that mothers adapt their touching behaviors according to negative infant facial affect; thus, when the infant displays negative facial affect, the mothers were less likely to initiate playful touch and more likely to initiate caregiving touch. Unexpectedly, only in the PPD dyads, were the mothers more likely to initiate affectionate touch when their infants were displaying negative facial affect. Our results also showed that mothers use specific touch types to regulate infants’ negative and positive affects; infants are more likely to initiate positive affect during periods with playful touch, and more likely to terminate negative affect during periods with caregiving touch.     

Interlimb coordination in prosthetic walking: effects of asymmetry and walking velocity

The present study focuses on interlimb coordination in walking with an above-knee prosthesis using concepts and tools of dynamical systems theory (DST). Prosthetic walkers are an interesting group to investigate from this theory because their locomotory system is inherently asymmetric, while, according to DST, coordinative stability may be expected to be reduced as a function of the asymmetry of the oscillating components. Furthermore, previous work on locomotion motivated from DST has shown that the stability of interlimb coordination increases with walking velocity, leading to the additional expectation that the anticipated destabilizing effect of the prosthesis-induced asymmetry may be diminished at higher walking velocities. To examine these expectations, an experiment was conducted aimed at comparing interlimb coordination during treadmill walking between seven participants with an above-knee prosthesis and seven controls across a range of walking velocities. The observed gait patterns were analyzed in terms of standard gait measures (i.e., absolute and relative swing, stance and step times) and interlimb coordination measures (i.e., relative phase and frequency locking). As expected, the asymmetry brought about by the prosthesis led to a decrease in the stability of the coordination between the legs as compared to the control group, while coordinative stability increased with increasing walking velocity in both groups in the absence of a significant interaction. In addition, the 2:1 frequency coordination between arm and leg movements that is generally observed in healthy walkers at low walking velocities was absent in the prosthetic walkers. Collectively, these results suggest that both stability and adaptability of coordination are reduced in prosthetic walkers but may be enhanced by training them to walk at higher velocities.     

Parade strippers: A note on being naked in public

This research studied the practice of exposing the female breasts in exchange for “throws” from Mardi Gras parade floats in the New Orleans area. Data were obtained from men who rode parade floats and from women who exposed themselves. Interviews were done with 51 women parade strippers and 54 male float riders. This phenomenon is compared to nudism, mooning, nude sunbathing, and streaking.     

Mothers’ attuned responses to infant affect expressivity promote earlier achievement of language milestones

To investigate infants’ affective expressivity and maternal attuned responsiveness to infant expressivity in relation to early language achievement, 77 dyads were visited in their homes at 9 and 13 months, and mothers were interviewed about their children’s language between 9 and 21 months. Maternal responses that were attuned to infant affect, by selectively matching either the gradient features or the valence of infants’ affective expressions, were more predictive of children’s language achievement than maternal nonmatching responses; and maternal matching responses at 9 months were more predictive of children’s language achievements than maternal responses at 13 months. Moreover, maternal matching responses at 9 months predicted second-year language achievements over and above infant affect expressivity at 9 and 13 months, and over and above maternal matching responses at 13 months. Infants’ affective expressivity per se was not predictive.