Cues to help use judge depth/distance:
–Primary •Convergence (eye muscles pull eyes inwards to focus on near objects) •Retinal disparity (process of stereopsis i.e. Our brain merges 2 images into 1) •Accommodation (lens changes shape depending on how far or near object is)
–Secondary (monocular cues) •Relative height, aerial size, shadowing, overlap, linear etc – pictorial cues.
If perception is innate ...
It is likely we are born with ability to use primary cues but ..... new born infants can’t co-ordinate their eyes very well – until about 3-12 months, it is probably not till about 6-12 months that retinal disparity is more accurate. So does the visual cliff experiment really test innate ability or learnt?
Testing ability to use secondary cues
Granrud & Yonus 1984. Do young infants use ‘overlap’ to decide if one object is in front of another?
If one object appears to partially cover another, we assume the first object is in front.
•This was investigated by Granrud and Yonus 1984.
Babies tend to reach for objects that are nearer
•Shapes A suggest depth because of overlap. –7 month old babies reached for the left shape –5 month old babies didn’t. •Shapes B and C don’t contain depth cues. –Neither age group reached for the left shape •Suggest babies are influenced by depth cues but the ability to perceive the overlap cue may not appear until 7 months of age.