3 months: Babies have directed arm movements and look back and forth between objects and hands {behavior, infant}. Babies can reach to touch but miss. Babies put objects or hands in mouth. Babies can laugh. Same-stimulus repetition is boring. Babies can sit with support.
3 months: Cortex begins to function, convolutions begin, conscious motor acts begin, and brain controls primitive reflexes {brain development, 3 months}. Cells in cortical layers five and six are functioning but not other cortical cells. Intraorganismic short circuit is present and stable. Parietal lobes are active.
3 to 4 months: Babies can know depth, orientation, size constancy, shape constancy, completion, motion parallax, and binocular parallax {cognition development, 3 to 4 months}. Using three dimensions and depth uses convergence and eye coordination. Babies recognize people as strangers. Infants watch their two hands as they contact and manipulate each other. Infants can distinguish human faces. Infants make sounds in response to internal states.
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Date Modified: 2022.0225