SIGHT
The human eye is an organ which reacts to light for several purposes. The rod and cone cells in the retina allow conscious light perception and vision including colour differentioniation and the perception of depth. The human eye can distinguish about 10 million colours. Receptors are groups of specialised cells. They can detect changes in the environment, which are called stimuli, and turn them into electrical impulses. There are around 120 million receptors in the eye. The eye’s specialized receptor cells is the light-receptive neuron in the retina of the eye.
DO WE REALLY PERCEIVE WHAT OTHERS DO?
What governs our perception of the world? As our full perception develops, our awareness of the world around us also develops. The brain is acting upon the information that it receives. Our senses are enriched. The enriched qualities which come from our knowledge of the world is projected into the world from the brain. The brain adopts strategies for making effective use of limited information on the basis of our past experiences.
THE BRAIN
The back of the brain is the primary and visual area. It connects to other areas which carry knowledge and information. For example, movement, colour, line and shape. It is estimated to contaon 15-33 billion neurons, each connected by synapses to several thousand other neurons.
BLACK BOX
The brain is locked away in a black box; not receiving any light (although we ‘see’ light). It receives signals lke morse code. The brain has to decode and interpret these codes, thus constructing the world around us. We actually ‘see’ very little. For example, when looking out into the sky, what the eye sees in the center is just about the size of the moon; everything else is kind of vague.
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The ear detects and receives sound and is part of the auditory system. Sound is a form of energy that moves through air, water, and other matter, in waves of pressure. The outer part of the ear collects the sound. That sound pressure is amplified through the middle portion of the ear. Sound waves are perceived by the brain through the firing of nerve cells in the auditory portion of the central nervous system. The ear changes sound pressure waves from the outside world into a signal of nerve impulses sent to the brain. The ear’s specialized receptor cells is the vibration-sensitive neurons in the cochlea of the ear.
DOES SIGHT DOMINATE SOUND? All senses act in isolation. Interaction doesn’t occur in every situation. Hearing, at least, has equal importance as vision. Sight can dominate the visual percept. An example is lipreading, we are doing so continuously, it is beneficial when the auditory signal is degraded.
THE MCGURK EFFECT
The McGurk effect is a perceptual phenomenon that demonstrates an interaction between hearing and vision in speech perception. The illusion occurs when the auditory component of one sound is paired with the visual component of another sound, leading to the perception of a third sound. The visual information a person gets from seeing a person speak changes the way they hear the sound. The power of the visual image alters perception of the auditory image.