Depth perception is the ability to perceive the world in three-dimensions. It does this via monocular and binocular depth cues. Previous research has shown that binocular judgements of depth are better than monocular judgements (Mckee et al., 2010). The current study looked at the effect of monocular and binocular vision when determining which of two objects were closer. It was hypothesised that two eyes would be better than one when judging depth perception. An experimental design was used in which a sample of 20 participants were asked to judge which of two identical pens was closer to them on a 10cm depth scale. The independent variable was whether participants were in the binocular or monocular condition and the dependent variable was the accuracy of depth perceptions. Correct or incorrect responses were recorded on a response scale. The results showed that participants in the binocular condition produced more correct answers than participants in the monocular condition, supporting the experimental hypothesis. This corresponds with previous research.
The Effect of Monocular and Binocular Vision when Judging Depth Perception
Depth perception in relation to physical stimuli comes from the study of psychophysics. Depth perception is the ability to see the world in three-dimensions and the distances of objects. The retina receives information in only two-dimensions, but the brain elicits information about depth so that we can perceive the world in three dimensions. It does this via visual and oculomotor cues. Some depth cues only require input from one eye; these are known as monocular depth cues. They include motion parallax; when moving forward, the way objects move past you can inform you as to how far they are, aerial perspective; objects become clearer the closer they are to you, relative size; if there are two objects that you know are the same size, the smaller one must be further away, interposition; if one object overlaps another you can judge which object is closer to you, texture gradient; the texture of an object is more difficult to see the further away it is, elevation; objects appearing higher in the visual field are perceived as being further away, shading, shadows of objects can help the brain determine how far away they are, and linear perspective; the perception that parallel lines angle towards each other as they recede into the distance (Schiffman, 1997). However, some sources of information require input from both eyes; this is known as binocular depth cues. These include binocular disparity; using two images of the same scene from slightly different angles. And convergence; the movement of eyes turning inwards, depending on the distance of the object your observing. The ability to perceive relative depth using binocular vision is known as stereopsis. Oculomotor cues derive from the act of muscular contraction, either from the focus of the lens or the position of the eyes (Sekuler, 2002). Oculomotor cues include convergence and accommodation. Accommodation is the process of your eyes adjusting to keep an object in clear focus. But why do humans have two eyes? Some animals, such as herbivores, have eyes on the side of their head. Evolutionary psychologists would argue that this enables them to notice the approach of predators and ensure survival. However, most predators need binocular vision and therefore have eyes in the front of their head enabling them to judge distances when looking for pray. Previous research has found that binocular depth cues provide more accurate information about depth. Mckee and Taylor (2010) investigated monocular and binocular depth cues when judging a pair of metal rods in a natural setting either in isolation, or surrounded by other objects, and found that the presence of objects and textures improved monocular judgements; however, binocular judgments were still more accurate. Similarly, Barlow, Blakemore and Pettigrew (1967) investigated monocular and...
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