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Sensation & Perception

Sensation

the process by which a stimulated receptor creates a pattern of neural messages that represent the stimulus in the brain

Perception

a mental process that elaborates and assigns meaning to the incoming sensory patterns

Core Concept of Sensation & Perception

The brain senses the world indirectly because sense organs convert stimulation into neural messages.

Transduction

the transformation of 1 form of energy to another - especially by the transformation of stimulus info into nerve signals

Sensory Adaption

loss of responsiveness in receptor cells after stimulation has remained unchanged for a period of time

Absolute Threshold

the amount of stimulation necessary for a stimulus to be detected

Difference Threshold

the smallest amount by which a stimulus can be changed

JND

just noticeable difference; same as difference threshold

Weber's Law

states that the size of a JND is proportional to the intensity of the stimulus

Fechner's Law

expresses the relationship between the actual magnitude of the stimulus and the its perceived magnitude

Steven's Power Law

the relationship between the magnitude of a physical stimulus and its perceived intensity or strength; more accurate than the other 2 laws

Signal Detection Theory

provides an accurate portrayal of sensation; occurs outside of consciousness; explains how we detect signals & states that sensation depends on stimulus characteristics, background stimulation & the detector

Subliminal persuasion

the brain perceives information below the level of the conscious mind using a variety of techniques (subliminal advertising)

Core Concept of Senses

Senses all operate in the same way but each extracts different info and sends it to its own specialized processing region in the brain.

Retina

thin, light-sensitive layer at the back of the eyeball which contains millions of photoreceptors & other nerve cells (where transduction occurs for sight)

Photoreceptors

light-sensitive cells (which include rods & cones) in the retina that convert light energy to neural impulses; the farthest place light reaches in the visual system

Rods

photoreceptors in the retina that are very sensitive to dim light but not to colors; allows you to function in near-darkness & cannot make distinctions to sense color

Cones

photoreceptors in the retina that are very sensitive to colors but not to dim light; each is specialized to detect the light waves we sense as blue, red, or green

Fovea

center of the retina that give us our most sharpened vision; we use this to scan any visual interest

Optic Nerve

transports visual information from the eye to the brain

Blind Spot

part of the retina that has no photoreceptors and is located at the point where the optic nerve exists each eye

Role of the Visual Cortex

transforms incoming neural impulses into visual sensations of color, form, boundary, & movement; transforms 2D patterns to 3D

Brightness

these sensations come from the intensity or amplitude of light & is determined by how much light reaches the retina; sensed by the level of neural activity produced in the retina & passed along optic paths

Physical Properties of Color

it is a psychological sensation, not a property of things in the external world; called a hue

Psychological Properties of Color

color exists only in the mind of the viewer & is a sensation that the brain creates based on the wavelength of light striking our eyes

Electromagnetic Spectrum

the entire range of electromagnetic energy, including radio waves, X-rays, microwaves, & visible light

Visible Spectrum

pure energy of a tiny part of the EMS to which our eyes are sensitive

Trichromatic Theory

3 receptor explanation for color vision & sensation; colors are sensed by 3 different types of cones sensitive to light in red blue & green wavelengths

Opponent-process Theory

the idea that bipolar cells in the visual system process colors in complementary pairs (red/green, blue/yellow); better explains some cases of color blindness

Color Blindness

typically a genetic disorder that prevents an individual from discriminating certain colors

Frequency

pitch; the number of vibrations or cycles completed by a wave in a given amount of time usually in a second

2 Physical Properties of a Sound Wave

frequency & amplitude

Amplitude

loudness/intensity; a measure of the physical strength of the sound wave

Tympanic Membrane

eardrum; receives vibrating waves of air & transmits them to 3 tiny bones which pass them on to the cochlea, the primary organ of hearing

Cochlea

where sound waves are converted into nerve messages

Basilar Membrane

a thin strip of tissue sensitive to vibrations in the cochlea; converts the vibrations into neural messages by hair cells (receives sound)

Role of the Auditory Cortex

processes neural messages to make experiences we know as music, whispers, shouts, doorbells, etc

3 Sensory Qualities of Sound

pitch, timbre, loudness

Pitch

a sound wave's frequency determines the highness or lowness of a sound

Loudness

determined by a sounds physical strength or amplitude

Timbre

the quality of a sound wave

Conduction Deafness

the ways in which sound waves are converted to nerve energy have been interfered with or interrupted; result of very loud sound or trauma

Nerve Deafness

linked with a deficit in the body's ability to transmit impulses from the cochlea to the brain; damage that has occurred to the auditory nerve; most people born death have this type

How are visual & auditory sensations alike?

Both sensations are processed by neural messages sent to the region of the cortex; different regions of the brain, when activated, produce different sensations

Vestibular Sense

the body position sense that orients us with respect to gravity & tells us how our bodies - especially our heads - are postured, whether straight, leaning, reclining, or upside down; also tells us when we are moving or how our motion is changing

Kinesthetic Sense

the body position sense that keeps track of body parts relative to each other; makes you aware of crossing your legs, for example & tells you which hand is closer to a ringing phone

Olfaction

sense of smell

Olfactory Bulb

where sensations of smell are realized

Pheromones

chemical signals released by organisms to communicate w/ other organisms of their species; often used by animals for sexual attractions, danger, food sources, etc

What 2 senses are based on chemistry?

smell & taste

Gustation & its 5 Qualities

sense of taste - sweet, sour, bitter, salty, umami (MSG)

Papillae

taste receptors

Where are taste sensations sent?

somatosensory cortex

Source of brain processing for touch

skin senses that are connected to the somatosensory cortex, located in the parietal lobes

Where is the greatest skin sensitivity?

where we need it the most - face, tongue, & hands

Experience of Pain

can arise from intense stimulation of various kinds, such as a very loud sound or heavy pressure; sensations of pain arise in the brain itself & not the damaged nerves in the sensory pathways

Gate-Control Theory

assertion that pain depends on relative amount of traffic in 2 different sensory pathways; an explanation for pain control that proposes we have a neural "gate" that can block incoming pain signals under some circumstances

Purpose of Pain

serves as an essential defense signal, warns us of potential harm & helps us survive in hostile environments

Placebo Effect

a response to a placebo (fake drug), caused by a subject's belief that they are taking real drugs

Pain Threshold

varies enormously from person to person

Relationship between Perception & Sensation?

Perception brings meaning to a sensation, so perception produces an interpretation of the world, not a perfect representation of it

Percept

what we perceive; the meaningful product of perception - often an image that has been associated with concepts, memories of events, emotions, and motives

Feature Detectors

cells that detect certain stimulus features such as length, slant, color and boundary

Binding Problem

the unknown knowledge of how the brain manages to combine (or bind) the multiple features it detects into a single percept (ex: a face)

Bottom-Up Processing

stimulus-driven processing; perceptual analysis that emphasizes characteristics of the stimulus, rather than our concepts and expectations; thorough but time consuming

Top-Down Processing

conceptually-driven processing; invokes a perceiver's goals, past experiences, knowledge, expectations, memory, motivations, or cultural back round; quicker & inferential

Perceptual Constancy

ability to recognize the same object as "constant" under the different conditions such as changes in illumination, distance, or location

Illusion

what occurs when your mind deceives you by interpreting a stimulus pattern in a manner that is demonstrably incorrect

Ambiguous Figures

stimulus patterns that can be interpreted in 2 or more ways; no right way

Gestalt Psychology

"whole"; emphasizes how we organize incoming stimulation into meaningful perceptual patterns; Gestalt psychologists believe that much of perception is shaped by innate factors built into the brain

Figure

a pattern that grabs our attention

Ground

backdrop against which we perceive the figure

Closure

allows us to see incomplete figures as wholes by supplying missing segments, filling gaps, and making inferences

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