Developmental Science最新文献

Numerical estimation is one of the key early math skills and predicts children's long-term math achievement. While children are born with an intuitive “number sense,” they do not form a mapping between nonverbal numerical representations and symbolic numbers until about 5 years of age. This protracted learning process is embedded in children's interactions with other people, although little is known about how children's existing social beliefs may influence how they receive numerical information from other people. Meanwhile, children in the United States develop a stereotype to associate men with being better at math at around 6 years of age. Does this gender stereotype influence how children receive numerical information from other people? Using a numerical estimation task, we showed 5- to 7-year-old children (N = 198; 93 girls; United States) competing answers from a male and a female informant before asking children to provide their own answer. We found that children's answers were biased by the male informant more than the female, even when the female was accurate. This bias was domain-specific, as there was no difference in children's performance on a memory control task. Furthermore, repeated exposure to inaccurate answers from a male informant (in contrast to accurate answers from a female informant) induced changes in children's estimation even when the informants were no longer present. Therefore, gender stereotypes may have profound impacts on how children acquire and process numerical information.

Summary

Infants' time spent in different body positions varies substantially within a day: lying supine on their backs, crawling or playing while prone on their bellies, sitting on the floor or in seating devices, standing or walking upright on two feet, and held by an adult. Infants may spend long periods in one position, such as sitting in a highchair, followed by periods of switching positions (e.g., prone and upright), such as during play. Speech input has been linked with infants’ placement and motor development. Here, we extend past work to ask whether adults speak more frequently depending on infants’ time spent in different body positions throughout the day. We gathered home recordings from 64 infants in two age groups, 4–7 months and 11–14 months, using movement sensors to measure body position and a LENA audio recorder to estimate adult word count. Data were analyzed in 10-min bins throughout the day to determine whether within-day differences in infants' time spent in each position were associated with the frequency of adult's speech. Indeed, increased time spent supine and prone predicted fewer adult words, whereas increased time sitting and held predicted increases in word count. Upright was age dependent, with more time spent upright predicting an increase in word count for younger infants, but a decrease for older infants. These findings reveal the importance of considering infants’ body position in understanding speech input and subsequent language development.

Summary

ABSTRACT

Success at a skill-based activity shows that a person is competent and likely to succeed again in the future. Success at a pure-chance activity, by contrast, does not imply competence or future success. In two experiments, we investigated children's developing understanding of how skill- and chance-based activities differ in relation to competence. In both experiments, children aged 4–7 (total N = 279) saw skill- and chance-based activities and judged whether a person who had previously succeeded with each activity would succeed when next attempting it. From Age 5, children were more likely to see past success as predictive of future success for skill- than chance-based activities. The second experiment also looked at judgments about agents who had previously failed and found that children at all ages predicted future success similarly regardless of whether activities involved skill or chance alone. This experiment also included a sample of adults (N = 202), and found their responses were overall comparable to those of 7-year-olds. Together, these finding are informative about development in children's reasoning about the predictive utility of past success, and potentially about their theory of performance—their understanding of factors that determine whether agents are likely to succeed. The findings provide preliminary evidence for development in this theory at Age 5 while also showing that its development is protracted.

Summary

The ability to follow another's gaze direction is a foundational skill in human cognition that underpins more complex social abilities. Other primate species also exhibit a variety of gaze-following behaviors, but previous experimental work has focused only on captive populations. Studies of cognition in wild animals are crucial to understanding the biological context of different psychological processes, as well as to characterize developmental change in cognition in animals interacting in natural social groups. We therefore conducted field experiments with wild chimpanzees (Pan troglodytes schweinfurthii) ranging from infancy to old age in Kibale National Park, Uganda. Chimpanzees observed a human demonstrator who either looked up on test trials or down on control trials across up to four trials presented on different days. We found that wild chimpanzees reliably followed the actor's gaze, looking up more often during test trials where she looked up compared to control trials where she looked down. We further characterized the development of this skill and found that whereas juveniles and younger adults consistently followed the demonstrator's gaze, infants and older adults did not. Our findings show that even chimpanzees without a history of social interactions with humans will reliably follow gaze, providing the first evidence that wild primates show such co-orienting responses. This work further provides support for the hypothesis that chimpanzees show distinct developmental trajectories for gaze-following compared to humans, even in wild social contexts.

Summary

It has been suggested that bilinguals take greater advantage of visual speech cues than monolinguals. Therefore, in a sample of 474 (47.3% females) monolingual and 101 (48.5% females) bilingual infants at 5 months of age, we examined the tendency to look at the eyes versus the mouth of dynamic faces, as well as the latency and ratio of looking at a static face interspersed with non-social objects. No significant differences were found for these measures, suggesting that monolingual and bilingual infants orient to and scan faces in a similar way. Although no association was found between the tendency to look at eyes versus mouth at 5 months and vocabulary at 24 and 36 months, a higher tendency to look at the eyes was related to a larger receptive vocabulary at 14 months, but only in the monolingual group (β = 0.15, 95% CI: 0.04; 0.27, p = 0.011). However, the difference in beta values of this association between mono- and bilinguals was not statistically significant. In conclusion, we did not find support for the hypothesis that bilingual infants rely on visual speech cues from the mouth more than monolinguals do, and there was no association between the tendency to look at eyes versus mouth and later language development in the bilingual group.

Summary

Variety in locomotor forms—upright (e.g., walking) versus non-upright (e.g., crawling)—reflects a “decision” about how to move. A decision about whether to move upright or non-upright reflects the costs incurred from getting into and moving in a particular posture—energy, stability, time, comfort, and so on. Are infants and caregivers sensitive to the immediate costs of upright and non-upright locomotion? We tested bout-level sensitivity to the costs of locomotor form in groups with different locomotor skills and body size (24 crawling and 24 walking infants and their caregivers). To encourage both short and long bouts, dyads played with toys clustered in a pile and toys dispersed around the room. Most critically, all groups showed bout-level sensitivity to the costs of upright and non-upright locomotion—they factored in their starting posture, typical mode of locomotion, and travel distance when deciding how to move. Walkers and caregivers only moved non-upright if they were already seated and traveled short distances; otherwise, they walked. Conversely, crawlers only moved upright if they were already standing and traveled short distances; if they were seated or moved long distances, they crawled. Moreover, across toy conditions, crawlers moved less than walkers and caregivers moved less than infants. Both crawlers and walkers displayed longer bouts when toys were dispersed, and caregivers mirrored their infants’ activity. Thus, despite infants’ propensity to move, babies—like adults—are indeed sensitive to the costs of upright versus non-upright locomotion.

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