•Perception works upwards from basic sensory input to the higher cognitive levels of the brain. •It is a direct process, inbuilt, adaptive for survival. •We actively interact with our environment and this is how we perceive things and construct meaning
1.All the information we need to perceive the world is contained in the pattern of light that reaches our eyes. This is called the optic array. 2.We pick up information from the way our bodies move, other things move and the constant movement of our eyes. This provides us with lots of information about the relative position of objects & surfaces. 3.The optic array contains information that stays constant even as we move – known as invariant information 4.Invariant information leads directly to perception
Some of the invariant information (things that rem
•The optic flow •Texture gradient •Horizon ratio
The optic flow
•We are surrounded by a rich sensory input – this allows us to understand our environment.
Optical flow patterns
•Gives us information about direction, speed & altitude. •As a plane lands, the runway in front appears motionless but the rest of the environment appears to fan out from that point. •When you are driving down the motorway the same thing happens - you know you are moving forwards. If you look out of the back window it happens in reverse.
Texture gradient – elements appear closer together the nearer they are
If the texture is coarse we assume it is close, as it become smoother, we assume it is further away.
Horizon ratio-The proportion of an object that is above and below the horizon on flat land, will stay constant no matter how close or far away you get.
•If objects are the same size they will all have the same horizon ratio this helps you decide how big something is.
But ... Perception doesn’t take place in a vacuum
•It is also affected by our –Physical state (where we are) –Psychological state (how we feel) –Physiological state (hungry etc) •Information from these states affects how we perceive things e.g. If thirsty we see a glass as something to drink from; if we’ve just picked some roses we might see it as a vase. •The same object offers different opportunities or ‘affordances’ •Bit controversial – not everyone agrees with this bit!
•Gibson 1955 – pilots could land a plane using the information present in the optic array (horizon, texture, movement). •Time-to-contact: speed & distance can be judged using direct visual info alone. Lee et al 1982 – videotaped long jumpers, they varied their final stride length to make sure their foot was in the right place for take off. •Lee et al 1980 Gannets can judge when to close wings, bottom up processing accounts for their estimate of speed etc as they dive. •Johansson 1973 lights on body, P’s could tell movement from the changing array of lights (babies & animals could too)
–real world research – high ecological validity. –Takes movement and light patterns into account which highly controlled lab studies don’t. –Real world applications – traffic approaching roundabouts •Limitations: –Affordances, not a good way of explaining the meaning of objects, trying to get round the idea of memory or prior experience.