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Sensation and PerceptionChapter 8, Section 2&3
Ishihara Color Test74 - 21
Sensation becomes Perception
Psychophysics
The study of the relationships between sensory experiences and the physical stimuli that cause them
Gustav Fechner
Our Five Senses
Sight
Vision is the most studied of all the senses
Light enters eye through pupilLens focuses light on the retina in the back of the eye
Retina made up of two types of light-sensitive cells
Rods – require less light to stimulate (night vision)Cones – require more light than rods before they
respond (less of these types of cells)
Retinal cells change light energy into neuronal impulsesImpulses transmitted down optic nerve to the brainBrain interprets the impulses in the visual cortex
located in the occipital lobe at the back of the brain
Light is a form of electromagnetic radiation known collectively as the electromagnetic spectrum
An object’s color depends on which wavelengths of light reach your eye from the visible spectrum
Hearing
Sound waves from the air pass through various bones until they reach the inner ear
The inner ear contains tiny hairlike cells that change the change the waves into neuronal signals
These signals are transmitted through the auditory nerve to the brain
Taste
Chemical senseAppropriate chemical molecules must stimulate
proper receptors in the taste buds of tongueReceptors for sour, salty, bitter and sweetThis information is then relayed to the brain along
with data about texture and temperature
Smell (Olfaction)
Chemical senseAppropriate gaseous molecules must come into contact with smell receptors in the noseMolecules enter as vapors and reach special membrane in upper part of nasal passagesMessages are sent through olfactory nerve to the brain
Cilia in nasal cavity
Touch
Receptors in skin provide information about pressure, warmth, cold and pain
Sensitivity varies across body due to number of receptors located in each piece of skin
KinesthesisThe sense of movement and body position
Helps to maintain posture and balance – otherwise, movements would be jerky and uncoordinated
Absolute Threshold
The weakest amount of a stimulus that a person can detect half the time
Difference Threshold
The smallest change in a stimulus that can be detected half the time
Weber’s LawSmall changes to stimuli are more noticeable at small levels(slight change in the volume of music is more noticeable when already listening at a low level)
Small changes to stimuli are less noticeable at large levels(slight change in the volume of music is more noticeable when already listening at the highest levels)
Signal-Detection TheoryStudies relations between motivation, sensitivity, and decision making in determining the presence or absence of a stimulus
Involves recognizing some stimulus against a background of competing stimuli
Subliminal MessagesBrief auditory or visual messages that are presented below the
absolute threshold
(means there is a less than 50% chance they will be perceived)
Monocular Depth CuesHints that help us perceiving distance and depth that can be used with just one eye
Size – bigger is nearerRelative height – further away appear on higher planeLight and shadowsInterposition – when viewing overlapping images, we know the whole object is in the front Linear Perspective – parallel
lines converge when stretched into the distance
Binocular Depth CuesHints that help us perceive distance or depth that depend upon both eyes
Convergence – our eyes turn inward to look at nearby objectsRetinal disparity – eyes actually see their own, slightly different picture. A large difference = close objectSmall difference = far object
Constancy
Tendency to perceive certain objects in the same way regardless of changing angle, distance or lighting
Ames RoomUses depth cues to distort our perception
Left side of the room sits back several feet from the perceived distance
Right side of the room rises up several feet from the perceived height
Beuchet Chair
Top of the chair is off in the background
Legs of the chair is in the foreground
Standing in just the right spot, the illusion is complete
Extrasensory Perception (ESP)
The ability to gain information by some means other than the ordinary senses
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