Sensation and Perception Ciccarelli and White Chapter 3 Introductory Psychology Spring 2014 Sensation and Perception • Sense- a system that translates outside information into activity in the nervous system • Sensation- the stimulus message coming from the senses • Transduction- process of converting stimuli • Perception- the process of giving meaning to that message Figure: What Do You See? ABC’s of Sensation • Sensation is the activation of receptors in the various sense organs • Sensory Receptors – Specialized forms of neurons – Not stimulated by other neurons – Stimulated directly by different kinds of energy (light waves, sound waves, etc) Sensory Energy • Wavelength- the distance between peaks in a wave of light and sound • Frequency- number of complete waves, or cycles, that pass a given point per unit of time • Amplitude- the distance between the peak and the baseline of a wave Figure: The Dimensions of a Wave Sensory Systems- How Information gets from Sensation to Perception • Your senses gather information through various forms of energy • This energy is encoded into neuronal activity • Neuronal activity relays signals to the brain Modification of Energy into Neuronal Activity • In some sensory systems the first step in sensation involves modifying the incoming stimulus – Accessory structures complete this modification • The second step in modification is transduction – Transduction is the process of converting incoming energy into neuronal activity – Transduction takes place at structures called receptors Transfer of Information through CNS • Coding translates the physical properties of a stimulus into neural activity • Sensory nerves transfer coded activity to the brain (Thalamus) • Coded information for all senses except smell goes to the Thalamus • Thalamus does some initial processing and sends information to the Cerebral Cortex • Cortex receives input and produces sensation and perception Review of Structures of Forebrain Review: Elements of a Sensory System Sensory Threshold – Sensory Thresholds • Weber’s Law of just noticeable differences – Ex: Sugar in Coffee (20%) » Already have 5 teaspoons, must add 1 teaspoon » Already have 10 teaspoons, must add 2 teaspoons » Coffee regular • Absolute Threshold • Subliminal Perception • Movie • Habituation and Sensory Adaptation The Science of Seeing • The Science of Seeing – Psychological Properties of Light • Three psychological aspects to light – Brightness – Color – Saturation Figure: The Spectrum of Electromagnetic Energy Structures of the Eye – The structure of the eye • • • • • • • Cornea Aqueous humor Iris Pupil Lens Vitreous humor Retina – Cones – Rods • Fovea • Optic Nerve • Blind Spot/ Optic Disc Figure: Major Structures of the Eye Figure: The Lens and the Retinal Image How the Eye Works • • • • • Left and Right Visual Fields Areas of the Retinas Where the information goes Optic chiasm Photoreceptors – Rods – Dark adaptation – Light adaptation – Cones Color vision – Color Vision • Trichromatic Theory • The Afterimage • Opponent-process theory – Lateral geniculate nucleus • Color Blindness Perception of Sound • What is sound • Properties of sound waves • Auditory Spectrum The Structure of the Ear The structure of the ear • The outer ear • The Middle ear • The inner ear – – – – Cochlea Basilar Membrane-resting place of the organ of Corti Organ of Corti- contains receptor cells for the sense of hearing Auditory Nerve- bundle of axons from the hair cells in the inner ear that run to the brain Figure: Structures of the Ear Figure: The Cochlea Perceiving Pitch – Theories of Pitch • Pitch- psychological experience of sound that corresponds to the frequency of the sound waves; higher frequencies are perceived as higher pitches • Place Theory • Frequency Theory • Volley Principle Types of Hearing Impairments – Types of Hearing Impairments • Conduction Hearing Impairment – Hearing aids • Nerve hearing impairment – Tinnitus – Cochlear implants Figure: Sound Waves and Waveforms Table: Intensity of Sound Sources Auditory Pathways to the Brain • Auditory nerve conveys information to the thalamus which then relays it. – Thalamus relays the information to the primary auditory cortex • Cells in the auditory cortex have preferred frequencies. • Auditory cortex also receives information from other senses. Chemical Senses • Chemical Senses – Gustation • Taste buds • Five basic tastes • Supertasters – Olfaction • Definitions • Olfactory receptor cells • Olfactory bulbs Smell, Taste, and Flavor • Smell and taste act as two components of a single system, known as flavor. – Scent and taste pathways converge in the cerebral cortex. • Both tastes and odors prompt strong emotional responses. • Variations in nutritional state affects: – One’s experience of taste and flavor. – One’s motivation to eat particular foods. Figure: The Olfactory System Olfactory System • Unique relationship between smell and memory. • Species variability in sensitivity to odor and dependency on smell for survival. – E.g., humans have about 9 million olfactory neurons while dogs have 225 million. – Many species have an accessory olfactory system that detects pheromones. Somesthetic Senses – Touch, Pressure, Temperature • • • • • • Types of sensory receptors Visceral pain, somatic pain Congenital analgesia Congenital insensitivity to pain with anhidrosis Phantom limb Pain Gate Control Theory Kinesthetic Sense/ Vestibular Sense – Kinesthetic Sense – Vestibular Sense • Otolith organs • Semicircular canals • Motion sickness ABC’s of perception • The ABC’s of Perception – Size, Shape, and Brightness – Gestalt Principles • • • • • • Figure-ground Proximity Similarity Closure Continuity contiguity Figure 3.20: Gestalt Principles of Perceptual Grouping Depth Perceptions Monocular Cues – Linear perspective – Relative size – Overlap – Aerial perspective – Texture gradient – Motion parallax – accommodation Linear perspective Relative Size Overlap Aerial Perspective Texture gradient Depth Perception • Binocular Cues – Convergence – Binocular Disparity Perceptual Illusions • • • • Hermann Grid Muller-Lyer Illusion The Moon Illusion Illusions of motion Hermann Grid Muller- Lyer Other factors that Influence perception • Perceptual sets • Top down processing • Bottom up processing Figure 3.18: Misperceiving Reality Which Line Is Longer? From Gardner "Optical Illusions from Figures that are Undecidable to Hot Dogs That Float, Scientific American, 222, 124, 127 Reprinted with permission Figure: Reversible Images Return Synesthsia • Disorder in which the signals from the various sensory organs are processed in the wrong cortical areas resulting in the sense information being interpreted as more than one sensation.