Chapter 3 : Sensation and Perception

PSY 200 JSRCC

Sensation

• Your window to the world

• Sensation refers to the process of sensing out environment through touch, taste, sight, sound and smell

• Sensation is the process by which out senses gather information and send to the brain

• Detection of physical energy by sense organs, which then send information to the brain

• Is the Process of acceptation the stimulus by the sense

Perception

• Interpreting what comes in your window

• Perceptions is the way we interpret these sensations and therefore make sense of everything around us

• Process of organizing and interpreting sensory information

General sensations Concepts

• Transduction

• The process of converting an external energy or substance into electrical acticity with the neurons

• Bottom-Up Processing

• Analysis that begins with the sense receptor and works up to the brain’s integration of sensory information

• Bottom- up processing taking sensory information and then assembling and integrating it

• Top-Down Processing

• Top- down processing: using models, ideas, and expectations to interpret sensory information

• Perceptual sets occur when our expectations influence our perceptions

• As when construct perceptions drawing on our experience and expectations

• Information processing guided by higher level mental processes

General Sensation Concepts

• Sensory receptors

• Specialized cell responsible for converting external stumuli into neural activity for a specific sensory system

• Specialized cells that detect stimulus information and transmit it to sensory (afferent) nerves and brain

Sensory thresholds

• Absolute Threshold

• The absolute threshold refers to the minimum level of stimulus intensity need to detect a stimulus half the time

• Difference Threshold (JND)

• Just noticeable difference

• Degree of difference that must exist between two stimuli before difference is detected

• Weber’s Law

• Principle that two stimuli must differ by a constant minimum percentage to be perceived as different

• Subliminal Perception

• Detection od Information below level of Conscious awareness

Selective Attention

• Cocktail Party Effect

• The cocktail party effect describes the ability to focus one’r listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversation

Vision

• Our most dominating sense

• We encounter waves of electromagnetic radiation

• Our eyes respond to some waves

• Our brain turns these energy to wave sensations into colors

Light

• Light

• Form of electromagnetic energy

• Wavelength

• The distance from the peak of one wave to the peak of the next

• Hue, or color

• Amplitude

• Brightness

• Purity

• Saturation. Or richness

The Eye

• Eye

• Light from the candle passes through the cornea and the pupil, and gets focused and inverted by the lens. The light then lands on the retina. Where it behind the process of transduction into neural impulses to be sent out through the optic nerve.

• The lens is not rigid: it can perform accommodation by changing shape to focus on near of far object

• Sclera

• White, outer part of the eye

• Helps maintain shape of the eye

• Protects the eye from injury

• Iris

• Color part of the eye

• A ring of muscle that form the colored portion of the eye around the pupil and controls the size of the pupil opening

• Pupil

• Opening in center of the iris

• Size controlled by muscles in iris

• Adjustable opening in the center of the eye

The Eye• Cornea

• Clear membrane just in front of the eye

• Transparent membrane covering the front of the eye – the

• Lens

• Transparent structure behind pupil that changes shape to cones images on the retina

• Retina

• Multilayered, light-sensitive surface at back of the eye

• Converts visual stimuli to neural impulses

• Inner surface of the eye

• Contains rods and cons

• Transduction

• Process by which our sensory system convert stimulus energy into neural messages

The Eye• Rods

• Enable us to see basic shapes and forms

• Allow us to see in low level of lights

• Sensitive to light

• Cones

• Requires more light than rods

• Used for color perception

• Enable humans to see color and fine detail in adequate light, by that do not function in dim light

• Fovea

• Tiny area in center of the retina at which vision is best

• Contains only cones

• Central point in the retina, around which the eye’s cones cluster

Visual Cortex

• Feature Detectors

• Neurons in primary visual; cortex that respond to particular features of a stimulus

• Parallel Processing

• Simultaneous distribution of information across different neural pathways

• Binding

• Integration of what is processed by different pathways or cells

Gestalt Principles

• Gestalt Psychology

• School of thought interested in how people naturally organize perception according to certain patterns

• Whole is different from sum of its part

• Figure/ Ground

• When figure-ground relationships are ambiguous, or capable of being interpreted in various ways, out perceptions tend to be unstable, shifting back and forth

Depth perception

• Depth perception

• Ability to perceive objects three- dimensionally

• Binoculars cues

• Combined images from two eyes

• Monocular cues/ Pictorial Cues

• Available from image in one eye

• Relative size

• Interposition; objects blocking the view of another perceived as closer

• Familiar size

• Familiar objects that appear small are inferred to be distant

Perceptual Constancy• Perceptual Constancy

• Recognition that objects are constant even though sensory input is changing

• Color: tendency to perceive object color as stable even inside conditions changing illumination

• Size: objects do not differ in size when viewed from different distances

• Size Constancy

• Experiences teach us about perspective

• Allows us to perceive objects to be the same size even when viewed from different distances

• Same size despite retinal image changes

• Shape Constancy

• Same shape despite orientation changes

• Color/ Brightness Constancy

• Color Constancy

• The tendency to perceive objects as retaining their color even though lighting conditions may alter their appearance

• Perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object

• Brightness Constancy

• Similar to color constancy

Hearing/Audition• Audition

• Sense of Hearing

• Hearing

• Sounds requires a medium, such as air or water, through which to move

• Sound

• Vibrations in air processed by auditory system

• Wavelength/.Frequency

• Frequency

• The number of complete wavelengths that pass a point in a given time

• Determines the pitch of a sound

• Amplitude

• Loudness of sound

• Measure in ID decibels

• Timbre

• Distinctive quality of a sound that distinguishes it from other sounds of the same pitch and loudness

Auditory Processing the Brain

• Inner ear= auditory nerve= temporal lobe

• Most fibers cross over midline between hemispheres

• Left ear = right hemisphere

• Right ear= left hemisphere

• Some fibers go directly to same –side hemisphere

Skin Senses• Skin Senses

• Skin senses detect touch (pressure, temperature and pain

• Touch (tactile)

• Skin is the body’s largest sensory organ

• Millions of skin receptors mix and match to produce specific perception

• Temperature

• Two separate sensory system- one for signaling warmth and the other for signaling cold

• Also have distinct spot on the skin that register only warmth or cold

• Pain

• Pain serves a function- it warns us of impending danger

• Gate-Control Theory

• Theory that the spinal cord contains a neurological “gate” that blocks pain signals or allows them to pass on to the brain

• “gate” opened by the activity of pain signals traveling uo small nerve fibers

• “gate” closed by activity in larger fibers of by information coming from the brain

Taste/Gustation

• Gustation- (taste) receptors are taste buds on tongue, Four basic tastes: sweet, salty, sour and bitter

• Taste: Savory sensations

• Sensory interaction

• The principle that one sense may influence another

• As when the smell of food influences its taste

• When one sense affects another sense, sensory interaction takes place. So, the taste of strawberry interacts with its smell and its texture on the tongue to produce flavor.

• B. Papillae/Taste buds

• Papillae

• Knoblike elevations on the tongue, containing the taste buds

• Taste buds

• Nests of taste-receptor cells

• Children have more taste buds than adults

• C. Sweet, sour, salty, bitter and umami

Smell• Smell (The Olfactory Sense)

• Olfaction (smell) receptors are located at top of nasal cavity

• Smell: the sense of scents

• Airborne chemical molecules enter the nose and circulate through the nasal cavity

• Vapors can also enter through the mouth and pass into nasal caity

• Receptors on the roof of the nasal cavity detect these molecules

• Olfactory epithelium• Lining the roof of the nasal cavity, contains a sheet of receptors cells for smell

• B. Smell and Emotion

• Major Histocompatibility Complex

The Balance and Movement Senses

• Kinesthetic

• Kinesthesis= (body posture, orientation, and body movement) results from receptors in muscles, joint and tendons

• The sense of body position and movement of body parts; also called kinesthes Proprioceptive Feedback

• Vestibular Sense

• The sense of body movement and position

• Including the sense of ba;ance

• Vestibular sense (sense of balance) results from receptors in inner ear Semicircular canals

• Sense organs in the inner ear, which contribute to equilibrium by responding to rotation of the head

Question

• 1: The Process through which the senses detect environmental stimuli them to the brain is called

• A: Consciousness

• B: Perception

• C: Sensation

• D: Reception

Question

• 2. ______________ is the process by which the brain actively organizes and interprets sensory information

• A: Consciousness

• B: Perception

• C: Sensation

• D: Reception

Question

• 3. The crossover point where the right visual field information goes to the left hemisphere is called the ____________.

• A:: Fovea

• B: Optic Nerve

• C: Retina

• D: Optic Chiasm

Answer

• 1: C

• 2: B

• 3: D