Infants' responsiveness to pictorial depth cues in preferential-reaching studies: a meta-analysis.

The findings of numerous preferential-reaching studies suggest that infants first respond to pictorial depth cues between 5 and 7 months of age. However, three recent preferential-reaching studies have found evidence of responsiveness to pictorial depth cues in 5-month-olds. We investigated these apparently contradictory results by conducting meta-analyses of the data from 5-month-olds who participated in preferential-reaching studies. The data from 16 samples, comprising 475 infants 5-5.5 months of age, were integrated. The results showed that the infants responded more consistently to depth relationships specified by pictorial cues under monocular than under binocular viewing conditions (p<.001), indicating that 5-month-old infants respond to pictorial depth cues. This effect remained significant (p<.001) when the individual experiments that had found significant results were omitted from the analysis. Although the majority of experiments were unable to find evidence of pictorial depth perception individually, this ability was clearly revealed when their results were combined.