Sensation and Perception Gateway to the outside world

Definitions  Sensation  The stimulation of sensory receptors and the transmission of sensory information to the Central Nervous System  Perception  The psychological process through which we interpret sensory information

Definitions  Absolute threshold  The weakest amount of stimulus that can be sensed  Difference threshold  The minimum amount of difference that can be detected between two stimuli

Absolute Threshold

Definitions  Sensory adaptation  The process by which we become more sensitive to weak stimuli and less sensitive to unchanging stimuli

Definitions  Signal-Detection Theory  The method of distinguishing sensory stimuli that takes into account not only the stimuli’s strengths but also such variable elements as the setting, your physical state, your mood, and your attitudes

Vision  How does sight work?  What are the main parts of the eye?  How does color vision work?  What is color blindness and what causes it?

Vision  Vision accounts for 80% of the sensory information processed by the brain  The key component of vision is light

Vision  Light is comprised of electromagnetic waves  The human eye sees a small portion of the spectrum of wavelengths  Visible light can be broken down into its key components

Vision  In order from shortest to longest: red, orange, yellow, green, blue, indigo, violet  The nonvisible ranges include ultraviolet and infrared

Parts of the Eye  Pupil  Controls the amount of light that enters the eye  Lens  The lens controls the clarity of the image  Retina  The surface upon which the image is projected

Parts of the Eye  Photoreceptors  Neurons which are sensitive to light  Information is transmitted via the photoreceptors to the brain  Rods  Sensitive to the brightness of light  Cones  Cones provide color vision

Vision Definition  Visual acuity  The sharpness of an image which is determined by the ability to see visual details in normal light  Measured by a Snellen Chart

Vision  Measured against a distance of 20 feet  Numbers show what a person would see against a normal person’s vision  Farsighted vs. nearsighted

Vision  Afterimages  Visual impression that remains after the original image is removed  Blind spot  Area vision which is blocked by lack of photoreceptors

How vision works

Color Blindness  Some people are unable to see normal color vision  Due to the absence or malfunction of the cones  Most common (99%) is red-green in which person has difficulty seeing shades of red or green  8% of males and 1% of females

Hearing  What two characteristics do every sound have?  What are the main parts of the ear and how do they work?  What are some causes of deafness?

Sound  Pitch  How high or low a sound is (frequency)  The frequency depends on the number of cycles per second  The more cycles, the higher the pitch

Sound  Pitch is measured in Hertz (Hz)  Over the course of time, we lose the ability to hear different frequency.  At age 25, you begin to lose your ability to hear over 15,000 Hz  Take the test  an-you-hear-this-hearing-test/ an-you-hear-this-hearing-test/

Sound  Loudness  The loudness of a sound is determined by the height of the sound wave  This is known as the amplitude  Loudness is measure in decibels (dB)

Sound  Loudness can be subjective  A person’s sensitivity to sound and the duration can influence perceived loudness

The Ear

 Pinea  Outer flap of tissue that is use to help funnel the sound to the eardrum  Eardrum  A thin membrane that vibrates when sound hits it  Hammer, Anvil, & Stirrup  Small bones in the middle ear which transmit the sound to the inner ear  Stirrup is smallest bone in the body

The Ear  Cochlea  Bony tube in the ear that contains the fluids and neurons needed to transmit sounds to the brain  Auditory nerve  Nerve that transmits neural impulses from the inner ear to the brain

Locating Sound  Determining locations of sounds is based upon the principles of stereo sound  The level measured in each ear helps to determine where the sound originated

Deafness  May be inherited or caused by injury, disease or old age  Two primary types of deafness  Conductive  Sensorineural

Conductive Deafness  Occurs due to damage to the middle ear  Usually aided by devices that amplify sound  Happens when the eardrum is ruptured or through aging

Sensorineural Deafness  Caused due to damage in the inner ear  May be mild, moderate or severe  Can be born this way or due to prolonged exposure to loud sounds  Can be aided by cochlear implants