Sensation Perception Psych 112 Fall 2012 Gloria Suarez

Sensation & Perception Psych 112 Fall 2012 Gloria Suarez Adapted from Xingyu Pan

Learning Objectives • After this lesson, you should: o Be familiar with the 5 senses and how the nervous system processes sensory information o Understand the distinction between sensation and perception o Understand the distinction between top-down and bottom-up processing

Perceptual Memory • • • I will give you a set of pictures to study Keep “face down” until told to start studying Study the images for 20 seconds Pass back image sheet Will be tested later (for fun!)

Sensation vs. Perception • Sensation Detection of physical energy by sense organs, which then send information to the brain • Perception The brain’s interpretation of raw sensory inputs

Principles of Sensation • Transduction The process of converting an external energy or substance (like light or sound) into electrical activity within neurons • Sense receptor Specialized cell responsible for converting external stimuli into neural activity for a specific sensory system • Sensory adaption Activation is greatest when a stimulus is first detected

Psychophysics • Absolute threshold: Lowest level of a stimulus needed for the nervous system to detect a change 50 percent of the time • Just noticeable difference: The smallest change in the intensity of a stimulus that we can detect • Weber’s Law

Bottom-Up vs. Top-Down Processing • Bottom-Up Processing: Processing in which a whole is constructed from parts • Top-Down Processing: Conceptually driven processing influenced by beliefs and expectancies • Parallel processing: The ability to attend to many sense modalities simultaneously

Perceptual Set • Set formed when expectations influence perceptions • Perception of objects is influenced by the context/environment

Perceptual Constancy • Perceive stimuli similarly across situations 1. Color constancy 2. Size constancy 3. Shape constancy

Perceptual Memory Test • Take out a sheet of paper • Try to remember the images you studied earlier • Draw the images you remember o Try to keep your drawings consistent with the drawings you studied

Discussion • Form groups of 3 -4 o Compare your drawings and share what they are o Do your drawings look similar or different? • Compare your original list • How the words have affected your memory?

Color Changing Card Trick!

The Role of Attention • Selective attention: Process of selecting one sensory channel and ignoring or minimizing others o Cocktail party effect • Inattentional blindness: failure to notice stimuli when our attention is focused elsewhere o Change blindness: inability to notice changes in the environment

The Visual System

Rods and Cones • Rods: • Enable us to see basic shapes and forms • Allow us to see in low levels of light • Cones: • Allow us to see in color • Sensitive to detail • Require more light than rods

Perception and the Visual Cortex

When We Can’t See or Perceive Visually Blindness The inability to see; the presence of vision less than or equal to 20/200 Motion blindness Visual agnosia Blindsight A disorder in which patients can’t seamlessly string still images processed by their brains into the perception of ongoing motion A deficit in perceiving objects A phenomenon in which blind people still make correct guesses about the visual appearance of things around them

Audition Ear canal Conducts sound waves to the eardrum Eardrum Membrane that vibrates in response to sound waves Semicircular canal One of three fluid-filled structures that play a role in balance Cochlea Converts vibration into neural activity Pinna Flexible outer flap of the ear, which channels sound waves into the ear canal

When We Can’t Hear • Conductive deafness Due to a malfunctioning of the ear Nerve deafness Due to damage to the auditory nerve Noise-induced hearing loss Due to damage to our hair cells from loud sounds Age-related hearing loss By-product of the loss of sensory cells, degeneration of the auditory nerve

Smell and Taste Somatosensory cortex Olfactory bulb Orbitofrontal cortex Thalamus Pons Medulla oblongata

Sense Receptors Smell • Olfactory receptors in our noses are sensitive to hundreds of different airborne molecules. Taste • Taste buds: Sense receptors in the tongue that respond to sweet, salty, sour, bitter, umami, and perhaps fat • Papillae: Bumps on the tongue containing numerous taste buds

Five Basic Tastes SALTY UMAMI SWEET SOUR BITTER

When we can’t smell or taste • Gradual loss of taste and smell can be part of normal aging • Can also result from diseases, such as diabetes and high blood pressure • Loss of smell or ability to identify odors o Damage to the olfactory nerve o Brain damage caused by disorders such as Parkinson’s and Alzheimer’s • Loss of sense of taste o Cancer patients

Three Different Body Senses

The Sense of Touch Free nerve ending Meissner’s corpuscle Ruffini ending Pacinian corpuscle Source: Adapted from Dorling Kindersley

Pain Deficits • Disorders of pain perception, called pain insensitivities, are associated with an increased risk of injury. • Children with pain insensitivity usually have a normal ability to discriminate touch, although not necessarily temperature. • As unpleasant as pain may be, it’s essential to our survival.

Reference • This presentation is adapted from previous work of Sara Festini in Fall 2011.

The Visual System & Light • The visible spectrum is a subset of the electromagnetic spectrum. • Additive and subtractive color mixing