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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
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Home | Pregnancy Timeline | News Alerts |News Archive Oct 31, 2014

The white of the eye (sclera), or how much of it is shown and at what angle,
plays a role in an infant's social response to adults and children.
Image credit: The Visible Embryo




Infants pick up social cues from your eyes

Humans are the only primates with large, highly visible sclera — the white part of your eye. Eyes play a significant role in our expressiveness — and how much sclera is showing can indicate either positive or negative emotions and attitude.

Wide-open eyes, exposing a lot of white, typically indicate fear or surprise. A thinner slit of exposed eye, such as when smiling, expresses happiness or joy. Averted eyes, as well as direct eye contact, may suggest fear or intimidation. So the eye white, or how much is shown, and at what angle, plays a role in social interactions among humans.

Adults are well attuned to social cues involving eyes along with facial and other body contortions. This sensitivity to social eye cues is hard-wired into the brains of adults and they often respond without consciously being aware that cues were given.

But it has been unclear whether the ability to distinguish social cues by eye shape exists early in brain development. Can it be considered a key feature of human social makeup?

A University of Virginia and Max Planck Institute study, published online this week in the journal Proceedings of the National Academy of Sciences, finds that the ability to respond to eye cues apparently develops early — during infancy at seven or so months.

“Our study provides developmental evidence for the notion that humans possess specific brain processes that allow them to automatically respond to eye cues.”

Tobias Grossmann PhD, a developmental psychologist, University of Virginia and one of the study’s authors.

Grossmann and his Max Planck Institute colleague Sarah Jessen used electroencephalography, or EEG, to measure the brain activity of 7-month-old infants while showing them images of eyes wide open, narrowly opened, and with direct or averted gazes.

They found infants’ brains responded differently depending on the expression suggested by the eyes they viewed, which were shown absent of other facial features. They viewed the eye images for only 50 milliseconds – which is much less time than needed for an infant of this age to consciously perceive this kind of visual information.

“Their brains clearly responded to social cues conveyed through the eyes, indicating that even without conscious awareness, human infants are able to detect subtle social cues,” Grossmann said.

The infants’ brain responses displayed a different pattern to sclera depicting fearful expressions (wide-eyed) to non-fearful sclera. They also showed brain responses that differed when viewing direct gaze eyes compared to an averted gaze.

Grossmann: “This demonstrates that, like adults, infants are sensitive to eye expressions of fear and direction of focus, and that these responses operate without conscious awareness. The existence of such brain mechanisms in infants likely provides a vital foundation for the development of social interactive skills in adults.”

The infants in the study wore an EEG cap, like a small hat, which included sensors that could detect brain signals and were sitting in the laps of their parents during the testing.

The human eye with its prominent white sclera is thought to facilitate social and cooperative interactions among humans. While there is evidence for brain mechanisms that allow for the unconscious detection of eye cues in adults, it is not known whether this ability of the human brain emerges early in ontogeny and can therefore be considered a key feature of human social functioning. The current study provides neural evidence for the unconscious detection of emotion and gaze cues from the sclera in 7-mo-old infants. Our findings demonstrate the existence of fast, efficient, and reliable social cue detection mechanisms in the human infant brain that likely provide a vital foundation for the development of social interactive skills.

Human eyes serve two key functions in face-to-face social interactions: they provide cues about a person’s emotional state and attentional focus (gaze direction). Both functions critically rely on the morphologically unique human sclera and have been shown to operate even in the absence of conscious awareness in adults. However, it is not known whether the ability to respond to social cues from scleral information without conscious awareness exists early in human ontogeny and can therefore be considered a foundational feature of human social functioning. In the current study, we used event-related brain potentials (ERPs) to show that 7-mo-old infants discriminate between fearful and nonfearful eyes (experiment 1) and between direct and averted gaze (experiment 2), even when presented below the perceptual threshold. These effects were specific to the human sclera and not seen in response to polarity-inverted eyes. Our results suggest that early in ontogeny the human brain detects social cues from scleral information even in the absence of conscious awareness. The current findings support the view that the human eye with its prominent sclera serves critical communicative functions during human social interactions.

The study was conducted at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany where Grossmann directs the Early Social Development Group.

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