In the numerosity task, children habituated to slides containing two objects. WS performed like normal controls. The language task involved discriminating between two photos of everyday objects. WS performed like DS and MA-matched controls, not like CA controls. Phenotypic outcomes may not correspond to infant starting states, which does not support the notion that cognitive modules are innately specified.
Acuity is tested by examining whether infants can discriminate vertical stripes from a grey field.
By 3 to 4 months of age, infants tend to see categories of colour like adults. Categorical perception of colour is tested by habituating infants to a colour and varying the wavelength of light. After habituating to a square, infants are not likely to dishabituate to a picture that merely implies the presence of the square. Early on, infants realize that an object's actual size remains the same despite changes in the size of its retinal image. Babies who are crawling display fear on the visual cliff.