WEEK 2- SIZE CONSTANCY Flashcards
What factors are ignored when we are achieving visual object constancy
size, position, lighting, colour (though in extreme cases these changes have an effect like massive stimuli, objects in the periphery, silhouettes, fruit)
what factors are more costly to object processing?
plane rotation, depth rotation
when can object constancy fail
in cases of brain damage or stroke
what terms can be used to refer to size in the world?
objective/ physical/ linear
what terms can be used to refer to subjective/ introspective size?
apparent/ perceived
what terms can be used to refer to size related to visual angle in the retinal input or o a projected surface like a mirrror window or thin frame ?
projected, proximal, angular, retinal
what are the arguments for whether we percieve the objective world or our projected input or neither
Gibson and Epstein argued for constancy in normal visual experience and said we can only access input projections by paying special attention. Rock argued that our intial percepts are closer to the projected stimulus
what did Hatfield 2012 argue?
said both the objective world and the projected stimulus are accessible to us and we can show this by careful use of instructions
what happens every time you double the distance of an object to the eye?
the retinal angle at your eye shrinks in half
what did Granrud and colleages investigate?
how size estimates change during a child’s development and the influence of distance on outdoor size estimates. they developed a metacognitive account of how we perceive object size
what is the Ames room
depth cues lead us to misperceive distance and this causes us to misestimate the objective size of one of the people being much smaller
what did Granrud claim about near distances?
even young children can estimate objective size quite accurately at distances up to 3. at near distances multiple depth cues eg accomodation, ocular convergence, binocular disparity, and motion parallax give accurate information about objective distance to an object. so do not need to use explicit distance compensation metacognitive strategies
what are size estimates like for intermediate distances (-6m)?
both children and adults are fairly accurate but they underestimate objective size slightly
what are size estimates like for greater distances (>15m up to at least 60m)
children under 10 years greatly underestimate the objective size of objects whereas older children and adults show nearly accurate size constancy.
what causes children to improve estimations of the objective size of distant objects?
Ho1- perceptual learning- children slowly learn to use visual cues (leibowitz, 1974 size distance invariance hypothesis). Ho2- metacognitive theory children learn to explicitly use a cognitive strategy of compensating for size changes with distance. without this strategy they greatly underestimate size for distances beyond 10m.
what does the size distance invariance hypothesis state
this claims that our visual system estimates the distance of an object then determines the objects objective, physical size based on its angular projected size on our retina, ie perceived distance causes our perception of size
what does Granrud argue about perceptual versus cognitive factors in size estimation
He claims that there is no developmental change in how distant objects appear to us. adults have learnt to estimate the objective size of objects accurately whatever the distance of the object by using explicit metacognitive strategies. these strategies compensate for objects looking smaller when they are further away
what skills let us estimate objective size?
merriman, moore and granrud 2010- children were asked which comparison disc had the same objective, physical size as the target disc at 61m or at 6m. children with better verbal and visuospatial reasoning skills were more accurate suggesting that these skills underlie metacognitive strategy use- and these verbal and visuospatial reasoning skills develop with age
what granrud 2009 study suggested that a metacognitive strategy is used to estimate object size at far distances?
children who could explain how distance affects image size usually were 1) quite accurate at estimating the objective size of objects 61 away and 2) often explicitly reported using a distance compensation strategy ‘i know if you go far it’s gonna look smaller’ so it will look like one of those [points at a small comparsion disc] but know it’s really one of these bigger ones. children who did not seem to fully understand how distance affects image size usually 1) underestimated the size of objects 61m away, and 2) did not report using a strategy. by 5 years most children roughly know how distance affects aparent size but it often takes years more for them to learn how to accurately apply this knowledge so they can explicitly use a distance compensation strategy.
what instructions were given to participants in granruds 2009 study to test when children use a metacognitive strategy?
apparent size: choose a comparison object that matches the size that the test object appears to be. objective size: choose a comparison object that matches the test object’s actual size regardless of it’s apparent size. given these instructions for near AND far object
what were the results of the granrud 2009 study?
older children are more likely to use a metacognitive strategy but it is strategy use (not simply age) that seems to predict whether objective size is underestimated at far (61m) distances
why does undercompensation occur when estimating objective size at far distances?
likely occurs because young children respond based on how the object looks and they do not use an appropriate metacognitive strategy.. note this underestimation is typically only 20-30 per cent
how do some adults and older children accurately estimate objective size at far distances?
because they know that distant objects look smaller than they are
why do some overcompensate when estimating objective size at far distances?
seems a clear marker of the use of a poor metacognitive compensation strategy since visual cues rarely suggest that a distant object is larger than it really is