Cultural differences in the development of face perception

The development of specialised face processing is shaped by postnatal social experience. Previous literature indicates cultural influences on face scanning, but when and how culture modulates the development of expert face processing remains unclear. Current interpretations are additionally restricted to highly controlled screen-based paradigms that lack the social presence and visual complexities common to social interactions. This thesis explores cultural differences in infants’ and adults’ face scanning during naturalistic dyadic interactions and within screen-based paradigms to cast light on possible mechanisms that can explain how the postnatal environment shapes face perception. Chapter 2 discusses the significant methodological challenges associated with the analysis of head-mounted eye tracking data and presents a semi-automatic computational solution as well as a novel data-driven method based on permutation testing. Chapter 3 adopts dual eye tracking techniques in Western Caucasian and East Asian adults to explore face scanning during dyadic interactions. Chapter 4 presents a methodologically refined follow-up study and reveals greater eye scanning in Japanese adults and more mouth looking in British/Irish individuals. Chapter 5 employs a cross-sectional screen-based paradigm to examine face scanning in British and Japanese infants (aged 10 and 16 months) and adults. Independent effects of culture and age are revealed, suggesting that cultural differences largely manifest by 10 months of age. Chapter 6 examines whether scanning strategies of British and Japanese 10-month-olds extend to dyadic interactions but finds that both groups predominantly scan the lower face region. Altogether, the thesis findings suggest that the manifestation of cultural differences in face scanning and the degree to which they can be observed depends on various factors, e.g., age, social presence, or the dynamic complexity of faces. Overall, this points to a highly adaptive face processing system that is shaped by early postnatal social experience and modulated by contextual factors

Is mere exposure enough? The effects of bilingual environments on infant cognitive development.

Bilinguals purportedly outperform monolinguals in non-verbal tasks of cognitive control (the 'bilingual advantage'). The most common explanation is that managing two languages during language production constantly draws upon, and thus strengthens, domain-general inhibitory mechanisms (Green 1998 Biling. Lang. Cogn. 1, 67-81. (doi:10.1017/S1366728998000133)). However, this theory cannot explain why a bilingual advantage has been found in preverbal infants (Kovacs & Mehler 2009 Proc. Natl Acad. Sci. USA 106, 6556-6560. (doi:10.1073/pnas.0811323106)). An alternative explanation is needed. We propose that exposure to more varied, less predictable (language) environments drive infants to sample more by placing less weight on consolidating familiar information in order to orient sooner to (and explore) new stimuli. To confirm the bilingual advantage in infants and test our proposal, we administered four gaze-contingent eye-tracking tasks to seven- to nine-month-old infants who were being raised in either bilingual (n = 51) or monolingual (n = 51) homes. We could not replicate the finding by Kovacs and Mehler that bilingual but not monolingual infants inhibit learned behaviour (experiment 1). However, we found that infants exposed to bilingual environments do indeed explore more than those exposed to monolingual environments, by potentially disengaging attention faster from one stimulus in order to shift attention to another (experiment 3) and by switching attention more frequently between stimuli (experiment 4). These data suggest that experience-driven adaptations may indeed result in infants exposed to bilingual environments switching attention more frequently than infants exposed to a monolingual environment

Early bilingual experience is associated with change detection ability in adults.

To adapt to their more varied and unpredictable (language) environments, infants from bilingual homes may gather more information (sample more of their environment) by shifting their visual attention more frequently. However, it is not known whether this early adaptation is age-specific or lasts into adulthood. If the latter, we would expect to observe it in adults who acquired their second language early, not late, in life. Here we show that early bilingual adults are faster at disengaging attention to shift attention, and at noticing changes between visual stimuli, than late bilingual adults. In one experiment, participants were presented with the same two visual stimuli; one changed (almost imperceptibly), the other remained the same. Initially, participants looked at both stimuli equally; eventually, they fixated more on the changing stimulus. This shift in looking occurred in the early but not late bilinguals. It suggests that cognitive processes adapt to early bilingual experiences

Cultural influences on face scanning are consistent across infancy and adulthood

The emergence of cultural differences in face scanning is thought to be shaped by social experience. However, previous studies mainly investigated eye movements of adults and little is known about early development. The current study recorded eye movements of British and Japanese infants (aged 10 and 16 months) and adults, who were presented with static and dynamic faces on screen. Cultural differences were observed across all age groups, with British participants exhibiting more mouth scanning, and Japanese individuals showing increased central face (nose) scanning for dynamic stimuli. Age-related influences independent of culture were also revealed, with a shift from eye to mouth scanning between 10 and 16 months, while adults distributed their gaze more flexibly. Against our prediction, no age-related increases in cultural differences were observed, suggesting the possibility that cultural differences are largely manifest by 10 months of age. Overall, the findings suggest that individuals adopt visual strategies in line with their cultural background from early in infancy, pointing to the development of a highly adaptive face processing system that is shaped by early sociocultural experience

A systematic review of physiological methods in rodent pharmacological MRI studies

Rationale: Pharmacological magnetic resonance imaging (phMRI) provides an approach to study effects of drug challenges on brain processes. Elucidating mechanisms of drug action helps us to better understand the workings of neurotransmitter systems, map brain function or facilitate drug development. phMRI is increasingly used in preclinical research employing rodent models; however, data interpretation and integration are complicated by the use of different experimental approaches between laboratories. In particular, the effects of different anaesthetic regimes upon neuronal and haemodynamic processes and baseline physiology could be problematic. Objectives: This paper investigates how differences in phMRI research methodologies are manifested and considers associated implications, placing particular emphasis on choice of anaesthetic regimes. Methods: A systematic review of rodent phMRI studies was conducted. Factors such as those describing anaesthetic regimes (e.g. agent, dosage) and parameters relating to physiological maintenance (e.g. ventilatory gases) and MRI method were recorded. Results: We identified 126 eligible studies and found that the volatile agents isoflurane (43.7 %) and halothane (33.3 %) were most commonly used for anaesthesia, but dosage and mixture of ventilatory gases varied substantially between laboratories. Relevant physiological parameters were usually recorded, although 32 % of studies did not provide cardiovascular measures. Conclusions: Anaesthesia and animal preparation can influence phMRI data profoundly. The variation of anaesthetic type, dosage regime and ventilatory gases makes consolidation of research findings (e.g. within a specific neurotransmitter system) difficult. Standardisation of a small(er) number of preclinical phMRI research methodologies and/or increased consideration of approaches that do not require anaesthesia is necessary to address these challenges

Cultural differences in the development of face perception

The development of specialised face processing is shaped by postnatal social experience. Previous literature indicates cultural influences on face scanning, but when and how culture modulates the development of expert face processing remains unclear. Current interpretations are additionally restricted to highly controlled screen-based paradigms that lack the social presence and visual complexities common to social interactions. This thesis explores cultural differences in infants’ and adults’ face scanning during naturalistic dyadic interactions and within screen-based paradigms to cast light on possible mechanisms that can explain how the postnatal environment shapes face perception. Chapter 2 discusses the significant methodological challenges associated with the analysis of head-mounted eye tracking data and presents a semi-automatic computational solution as well as a novel data-driven method based on permutation testing. Chapter 3 adopts dual eye tracking techniques in Western Caucasian and East Asian adults to explore face scanning during dyadic interactions. Chapter 4 presents a methodologically refined follow-up study and reveals greater eye scanning in Japanese adults and more mouth looking in British/Irish individuals. Chapter 5 employs a cross-sectional screen-based paradigm to examine face scanning in British and Japanese infants (aged 10 and 16 months) and adults. Independent effects of culture and age are revealed, suggesting that cultural differences largely manifest by 10 months of age. Chapter 6 examines whether scanning strategies of British and Japanese 10-month-olds extend to dyadic interactions but finds that both groups predominantly scan the lower face region. Altogether, the thesis findings suggest that the manifestation of cultural differences in face scanning and the degree to which they can be observed depends on various factors, e.g., age, social presence, or the dynamic complexity of faces. Overall, this points to a highly adaptive face processing system that is shaped by early postnatal social experience and modulated by contextual factors