Brenda K. Todd

Dynamic aspects of visual event perception and the production of pointing by human infants

The aim of this study was to investigate the relationship between pointing production in infants and two types of event perception factors: spatial localization (e.g. eccentricity of visual events with respect to an initial fixation point) and salience of targets (addition to visual events of sound or object translation through space). Three experiments revealed that target characteristics, such as internal movement, sound, vanishing and translation through space (including disappearance) significantly influenced the incidence and latency of pointing, whereas the main effect of target localization was to determine which hand does the gesture. In particular, there was an advantage to the right side of the visual field in eliciting pointing when there is competition between targets. Finally, for events involving auditory-visual stimulation females made more right-handed points than males. The general advantage of the right hand for pointing may offer further evidence for a specific link between pointing, cerebral dominance and the transition to speech.

Her heart is in the right place: an investigation of the ‘heartbeat hypothesis’ as an explanation of the left side cradling preference in a mother with dextrocardia

A majority of mothers, whether right- or left-handed, exhibit a preference to hold their babies to the left of the body midline. One of the earliest explanations for this finding proposed that babies were being held close to the mothers heart [Salk, L. (1960). World Mental Health, 12, 168–175]. Salk suggested that the foetus becomes imprinted on the sound of the maternal heartbeat in utero. This paper reports a left holding preference in a mother who has the heart positioned on the right rather than the normal left side of the body. Salks ‘heartbeat hypothesis’ is not supported by the holding preference of the dextrocardiac mother, nor by the detailed patterns of holding in the control group.

The transmission of trauma in refugee families: associations between intra-family trauma communication style, children’s attachment security and psychosocial adjustment

ABSTRACT This study explores the transmission of trauma in 30 Middle Eastern refugee families in Denmark, where one or both parents were referred for treatment of PTSD symptoms and had non-traumatized children aged 4–9 years. The aim of the study was to explore potential risk and protective factors by examining the association between intra-family communication style regarding the parents’ traumatic experiences from the past, children’s psychosocial adjustment and attachment security. A negative impact of parental trauma on children might be indicated, as children’s Total Difficulties Scores on the Strengths and Difficulties Questionnaire (SDQ) were significantly higher than the Danish norms. A negative association between children’s attachment security as measured by the Attachment and Traumatization Story Task and higher scores on the SDQ Total Difficulties Scale approached significance, suggesting that the transmission of trauma may be associated with disruptions in children’s attachment representations. Furthermore a significant association between parental trauma communication and children’s attachment style was found.

Lateralization of infant holding by mothers: A longitudinal evaluation of variations over the first 12 weeks.

ABSTRACT The maternal preference to hold infants on the left rather than right side of the body was examined longitudinally, with attention to 4 explanations: maternal monitoring of infant state, maternal handedness, infant proximity to the mothers heartbeat, and preferred infant head position. The side and site of holding were measured over the first 12 weeks of the lives of 24 infants. Information about group and individual consistency in holding side allowed novel evaluation of the theories. A strong bias to hold on the left dropped below significance when the infants were aged 12 weeks and was limited to specific holding positions. Findings were generally consistent with the monitoring hypothesis, and little support was found for the 3 alternative explanations.

The association between psychological stress and miscarriage: A systematic review and meta-analysis

This systematic review and meta-analysis was designed to investigate whether maternal psychological stress and recent life events are associated with an increased risk of miscarriage. A literature search was conducted to identify studies reporting miscarriage in women with and without history of exposure to psychological stress (the only exposure considered). The search produced 1978 studies; 8 studies were suitable for analysis. A meta-analysis was performed using a random-effects model with effect sizes weighted by the sampling variance. The risk of miscarriage was significantly higher in women with a history of exposure to psychological stress (OR 1.42, 95% CI 1.19–1.70). These findings remained after controlling for study type (cohort and nested case-control study OR 1.33 95% CI 1.14–1.54), exposure types (work stress OR 1.27, 95% CI 1.10–1.47), types of controls included (live birth OR 2.82 95% CI: 1.64–4.86). We found no evidence that publication bias or study heterogeneity significantly influenced the results. Our finding provides the most robust evidence to date, that prior psychological stress is harmful to women in early pregnancy.

Putting the “Joy” in joint attention: affective-gestural synchrony by parents who point for their babies

Despite a growing body of work examining the expression of infants’ positive emotion in joint attention contexts, few studies have examined the moment-by-moment dynamics of emotional signaling by adults interacting with babies in these contexts. We invited 73 parents of infants (three fathers) to our laboratory, comprising parent-infant dyads with babies at 6 (n = 15), 9 (n = 15), 12 (n = 15), 15 (n = 14), and 18 (n = 14) months of age. Parents were asked to sit in a chair centered on the long axis of a room and to point to distant dolls (2.5 m) when the dolls were animated, while holding their children in their laps. We found that parents displayed the highest levels of smiling at the same time that they pointed, thus demonstrating affective/referential synchrony in their infant-directed communication. There were no discernable differences in this pattern among parents with children of different ages. Thus, parents spontaneously encapsulated episodes of joint attention with positive emotion.

A comparative perspective on lateral biases and social behavior

Cerebral lateralization and associated motor behaviors were historically thought to be characteristics unique to humans. Today, it is clear that these features are present and visible in other animal species. These shared attributes of brain and behavior suggest inheritance from a distant common ancestor. Population-level motor biases are likely to reflect an early evolutionary division of primary survival functions of the brains left and right hemispheres. In modern humans, these features may provide a foundational platform for the development of higher cognitive functions, inextricably cementing the ties between the evolution and development of cognition. This chapter focuses on the links between a vertebrate-wide right hemisphere dominance for perceiving and producing social signals, left side motor biases (inclusive of visual field preferences), and the evolution and development of cognition in modern humans.