Sensation and Perception CHAPTER 4 Sensation and perception form our world. Sensation is processed by physical receptors; perception is a psychological function of interpretation. Sensation and Perception © West Educational Publishing EXIT

Sensory Processes Sensation Perception Sensation is the process of receiving information from the environment through remarkable receptors in the human body. Perception Perception is the psychological process of organizing sensory information to make it meaningful. These two processes are intermixed. © West Educational Publishing EXIT

The body receives information through the five main senses. Vision Taste The Five Human Senses Smell Hearing Touch © West Educational Publishing EXIT

An absolute threshold is the minimal amount of sensory stimulation needed for a sensation to occur. © West Educational Publishing EXIT

Vision is the dominant sense. Click on the arrows for more information. Retina Iris Pupil Blind Spot Cornea © West Educational Publishing EXIT

The Iris The iris is a muscle that opens and closes in order to control the amount of light entering the eye. Iris Click for more information. Cornea Blind spot Iris Pupil Retina © West Educational Publishing EXIT

The Cornea The cornea is the outer covering of the eye. Cornea Cornea Click for more information. Cornea Blind spot Iris Pupil Retina © West Educational Publishing EXIT

The Pupil The pupil is the opening in the eye. Pupil Cornea Blind spot Click for more information. Cornea Blind spot Iris Pupil Retina © West Educational Publishing EXIT

The Retina The retina is the back of the eye that has receptors for light. Retina Click for more information. Cornea Blind spot Iris Pupil Retina © West Educational Publishing EXIT

The Blind Spot The blind spot is where the optic nerve exits and there are no receptors for light waves. Blind Spot Click for more information. Cornea Blind spot Iris Pupil Retina © West Educational Publishing EXIT

Blind Spot Demonstration Close your left eye and stare at the dot and move either forward or backward until the cube disappears. © West Educational Publishing EXIT

Rods Rods are visual receptors that “see” only black and white and are most sensitive in low light. Cones Cones are visual receptors that receive color and are most sensitive in daylight. © West Educational Publishing EXIT

Rods and Cones 7-8 million 120-125 million How many? Where concentrated? Sensitive to light? Sensitive to color? 120-125 million 7-8 million Periphery of retina Center of retina Very sensitive Low sensitivity Yes No © West Educational Publishing EXIT

Color Vision Some people cannot tell the difference between certain colors. The most common form is the inability to see the colors of red or green. © West Educational Publishing EXIT

The Structure of the Ear Cochlea This structure is a snail-shaped part of the ear that has tiny hairs and fluid that vibrate with incoming sound. Cochlea Eardrum Eardrum This is a piece of skin stretched over the entrance to the ear and vibrates to sound. © West Educational Publishing EXIT

Sound Audition Sound is energy; it travels in waves like light, but much slower. Characteristics Pitch: how high or low a sound is Timbre: complexity of tone Intensity: loudness (measured in decibels) © West Educational Publishing EXIT

Cutaneous Senses (Touch) There are 3 types of receptors: for pressure for temperature for injury or poison © West Educational Publishing EXIT

Smell (Olfaction) The sense of smell performs a critical role in providing information about the food we eat. It is very closely related to the sense of taste. Animals also use smell (chemicals called pheromones) to communicate sexual interest. © West Educational Publishing EXIT

Taste Taste receptors on the tongue are called taste buds. Salty Sweet Sour Bitter Taste receptors on the tongue are called taste buds. There are four types of taste receptors: salty, sweet, sour, and bitter. These receptors combine sensations to create subtle flavors. © West Educational Publishing EXIT

Perception Perceptual constancies use memory to maintain order in the world. Size constancy: ability to remember the size of an object no matter where it is located Color constancy: ability to perceive an object as the same color regardless of the environment Shape constancy: ability to perceive an object as having the same shape regardless of the angle Space constancy: ability to judge distance by perceiving either self or object movement © West Educational Publishing EXIT

Perceptual Organization Gestalt: making incomplete organization whole (they way something should be rather than how it actually is) Similarity: grouping like things together Proximity: grouping things together that are near each other Closure: filling in the missing details © West Educational Publishing EXIT

Perceptual Organization Closure Proximity Similarity © West Educational Publishing EXIT

Perceptual Illusions Which line is longer? Illusions are misperceptions. They illustrate how we organize objects into meaningful perceptions . Franz Müller-Lyer designed this illusion in 1889. Which line is longer? © West Educational Publishing EXIT

The Vertical-Horizontal Illusion Are the two lines the same length? © West Educational Publishing EXIT

Figure-Ground Illusion In the figure-ground illusion, the figure is in the front while the ground is in the back. Do you see the faces facing one another or do you see the vase? © West Educational Publishing EXIT

Which cylinder is largest? Click the forward arrow to move the cylinder on the right forward to the middle cylinder. © West Educational Publishing EXIT

Which cylinder is largest? Now click the forward arrow to move the cylinder forward to the front cylinder. © West Educational Publishing EXIT

Which cylinder is largest? © West Educational Publishing EXIT

Summary of Main Topics Covered Sensory Processes Vision Hearing Touch Smell Taste Perception © West Educational Publishing EXIT