How Adaption Experiments Contribute to Visual Perception
How have adaptation experiments contributed to the understanding of visual perception?
Perception involves the input of basic information from a retinal image. Retinal images can be ambiguous in terms of size and orientation of lines, blood vessels infront of the retina, eye tremors and the blind spot can affect perceptual responses. One retinal pattern can lead to different interpretations and distorted images from inadequate sensory data, but perception of something as a recognisable object remains stable despite variations in the retinal image, such as light, or position of the object. Perception is a process of construction, a stable, veridical or true representation of the world which needs to be constructed. The retinal image can be ambiguous due to different sizes, slants or distances, but still leads to a particular interpretation of the object.
Eye movements are not a series of fixations, clips of static images, but smooth movements resulting in a continually moving image. Shadows of blood vessels over receptor cells in the retina can lead to distortions in the retinal image, but the eye takes information from the environment to the brain for a perception to be constructed. People do not see ‘snapshots’ of the world, the eye and optic nerve does not send pictures to the brain, it transmits information regarding the patterns of light that hit the retina.
The visual pathway involves the retina, which includes photoreceptors, rods and cones. Rods are sensitive to dark and light, cones are responsive to colour. Both form a layer at the back of the retina. Retinal ganglion cells (RGC) form another layer infront of the photoreceptors, RGC axons leave the eye and form the optic nerve.
Adaptation occurs in the retina to adjust the sensitivity of receptors and vary the light intensity. Sensitivity is mainly adjusted by adaptation to match the light intensity at that moment. There is also light adaptation, going from a dark to bright environment, a quick process, and dark adaptation going from a bright to dark environment which takes longer.
Items can be recognised by a key or sign stimulus of the object such as angels or features that don’t vary even if the image changes. Barlow (1972) suggested that single cells in the visual pathway act as feature detectors, cells are tuned to respond when particular features are present. Barlow also proposed that cells and neurons are arranged in a hierarchy with...