Visual Cues & Constancies: Depth Cues (AQA GCSE Psychology)
Revision Note
Written by: Claire Neeson
Reviewed by: Lucy Vinson
Monocular depth cues
Depth cues are made up of information taken from the surrounding environment which help humans to understand depth i.e. that the world is 3-D rather than flat and depthless
A visual cue is any environmental stimulus which provides humans with information about spatial dimensions, movement, distance and proximity of objects and people within the visual field
Visual constancy is the ability of humans to understand that objects remain the same size even though they may appear smaller or larger depending on where they are located in the visual field (e.g. a cow which is far away in a field appears smaller than cows standing near the fence)
Humans use a perceptual system of visual cues and constancies to enable them to understand depth
Monocular depth cues are those which allow someone to judge distance and depth using only one eye (‘mono’ = ‘one’) i.e. if one eye is covered it is still possible to understand that an object is not smaller simply because it is seen in the distance
Monocular depth cues (which interpret the world as being in 2-D) include:
Linear perspective: this occurs when parallel lines (such as those on a railway track) appear to converge in the distance
Relative size: the further away an object/person is from the viewer, the smaller they appear in the visual field
Height in plane: objects/people who are higher up in the visual field appear to be further away from the viewer
Occlusion: when one object/person is obscured by another object/person they appear further away in the visual field
Monocular Depth Cue Example
Linear perspective is a monocular depth cue.
Binocular depth cues
Binocular depth cues are those which involve the use of both eyes (‘bi’ = ‘two’)
Each human eye takes in a slightly different view when both are used together and this is what enables human beings to use depth perception (see the image below):
Binocular Depth Cue Example
Retinal disparity: each eye takes in a slightly different view from the other.
Each eye takes in a view that is processed by the brain to create a 3-D image: the fact that each eye takes in a slightly different view is due to retinal disparity (if human eyes took in the same view they would have to be stacked on top of each other which would be of no use whatsoever!)
Objects/people which are further away do not produce as much retinal disparity as those which are closer to the viewer - this is due to convergence i.e. the eyes coming together to take in the view
Both retinal disparity and convergence allow human beings to process and understand depth
Animals such as birds have poor depth perception as they are only able to use monocular depth cues due to the placement of their eyes
Examiner Tips and Tricks
Make sure that you know all of the key terms for both monocular and binocular depth cues - and don’t get them mixed up! Make a table/grid and put it in your planner or above your desk to remind yourself of which depth cues are monocular and which are binocular.
Worked Example
Here is an example of a question you might be asked on this topic - for AO1 and AO2.
AO1: You need to demonstrate knowledge and understanding of key concepts, ideas, theories and research.
AO2: You need to apply your knowledge and understanding, usually referring to the ‘stem’ in order to do so (the stem is the example given before the question)
AO3: You need to analyse and evaluate key concepts, ideas, theories and research.
After each featured question there is a ‘model’ answer i.e. one which would achieve top marks in the exam.
Briefly outline two of the monocular depth cues shown in the image above. Explain how each cue you have identified helps us to perceive the distance of objects in this image. [4]
AO1 = 2 marks
AO2 - 2 marks
Model answer: (remember that you only need to use two of the following cues, we have presented you with a choice of several possibilities here):
AO1:
Height in plane is concerned with the position of the objects in the visual field;
Relative size is how large the same or similar objects appear to be in the visual field;
Occlusion is concerned with whether objects overlap’ linear perspective is the appearance of parallel lines converging;
AO2:
Height in plane – the person on right (walking near the second umbrella down) is higher in the visual field than the person in profile on the right of the image, so we know that the person near the second umbrella on the right is further away than the person in profile;
Relative size - the people further away in the image appear smaller than those who are in the foreground;
Occlusion - some of the shops on the right side of the image are occluded by tables and umbrellas so they appear further away; linear perspective - the straight lines of the road appear to converge in the distance;
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