Orig­i­nal archive video of Gib­son and Walk’s Visual Cliff exper­i­ment: test­ing infant depth per­cep­tion by get­ting them to walk over glass plates sus­pended above a drop.

The researchers wanted to find out whether 6 to 14 month-old infants could per­ceive depth.

The study put the infants, one at a time, in the mid­dle of a table, with one side replaced by glass so you could see the ‘drop’.

Their moth­ers would try and tempt them over both sides, and if the kids had no depth per­cep­tion, the glass ‘drop’ wouldn’t seem scary and they’d just walk straight over. Those who could see the ‘drop’ would avoid it.

Pretty much none of the infants wanted to walk across the ‘visual cliff’, sug­gest­ing that even kids of 6 months old could per­ceive depth.

But what of infants younger than this? When does depth per­cep­tion develop?

In 1973, a study by psy­chol­o­gist Andrew Schwartz placed five and nine-month olds on each side of the ‘visual cliff’ and mea­sured their heart rate.

When placed over the glass ‘drop’, the five month olds typ­i­cally showed no increase in heart rate, sug­gest­ing there was no dan­ger response. This sug­gests depth per­cep­tion prob­a­bly kicks in between about five and six months old.

via Mind Hacks