sensation and perception

Sensation: Gathering Information

Perception: Interpreting Information

/

Senses and the World

• Stimuli: something external that promotes a physical response

• Sensory neurons are continually inundated with stimuli

Senses:

• Sight- Visual Sense

• Hearing - Auditory Sense

• Taste- Gustation (Taste)

• Touch- Touch Sense

• Smell- Olfactory Sense

Sensation and Perception

Sensation:

• The processes by which our sense organs receive information from the environment

Transduction: 

• The process by which physical energy is converted into sensory neural impulses

Perception:

• The process by which people select, organize, and interpret sensations

Sensation and Perception Processes 

1. Sensation:

• Stimulus Detection: Sensory organs (e.g., eyes, ears, skin) detect external stimuli (light, sound, touch, etc.).

• Transduction: Sensory receptors convert the physical stimuli into electrical signals.

• Transmission: The electrical signals are sent to the brain via the nervous system.

2. Perception:

• Organization: The brain organizes the incoming sensory data.

• Interpretation: The brain interprets the data based on past experiences, knowledge, and context.

• Perceptual Experience: The brain creates a conscious experience (e.g., seeing a face, hearing music, feeling an object).

Coding

The process in which neural impulses:

• Travel by different routes To different parts of the brain

• Allowing us to detect different types of physical stimuli as different sensations

Feature Detectors = Specialized Neurons

• The brains of humans and other animals contain specialized neurons (cells)

• Respond only to certain sensory information and maximally to face

Vision

Your eye has two types of sensory receptors:

• Rods: are active in Dim lighting 

• Cones: responsible for color vision and fine detail

Trichromatic Theory

• T. Young (1802) & H. Von Helmholtz (1852)

• Both proposed that the cones in the eye detect 3 primary colors: red, blue, green

• Said all other colors can be derived by combining these 3

The Color Wheel

• Spectral colors vary from violet-blue to red

• Opponent colors are directly across from each other on the wheel

Opponent-Process Theory:

• Color vision comes from 3 pairs of opposing receptors

• The opponent colors are blue and yellow, red and green, and black and white

• This theory explains afterimages and color deficiency

Afterimage:

• Image you see after staring at something 

• For example: when you look at a projector light and then look away

Optic nerve: Pathway that carries visual information from the eyeball to the brain

Retina: Light sensitive inner surface of the back of they eye, which contains the receptor cells for vision

Hearing

Audition: the sense of hearing

Outer Ear: the pinna, auditory canal, and eardrum structures, which funnel sound waves to the middle ear

Middle Ear: The hammer, anvil and stirrup structures of the ear, which concentrate eardrum vibrations onto the cochleas oval window

Inner Ear: The semicircular canals, vestibular sacs, and cochlea, which generate neural signals that are sent to the brain

Cochlea: the fluid-filled, coiled tube in the inner ear that contains the receptors for hearing

Place theory for hearing: the theory the pitch perception is linked to the particular spot on the cochleas basilar membrane that is most stimulated

Frequency theory for hearing: The theory that pitch perception depend on how often the auditory nerve fires

Volley principle for hearing: An explanation for pitch perception suggesting that clusters of neurons take turns firing in a sequence of rhythmic volleys, and that pitch depends on the frequencies of these volleys.

Conduction hearing loss: a type of hearing loss that results from damage to the mechanical system that conducts sound waves to the cochlea; also called conduction deafness

Sensory hearing loss: A type of hearing loss resulting from damage to the cochleas receptor (hair) hearing cells or to the auditory nerve; also called nerve deafness

Auditory Localization

• The ability to judge from which direction a sound is coming

• Sounds from different directions are not identical as they arrive at left and right ears

• The brain calculates a sounds location by using differences in timing and intensity

Smell

Olfactory System: Structures responsible for the sense of smell

Sense of Taste

Taste Buds: nets of taste receptor cells

Gustation: The sense or act of tasting; receptores are located in the tongues taste buds

Selective Adaptation = Habituation

• A decline in sensitivity 

• To a stimulus due to constant exposure to it

• Example: trains, sirens, loud talking

Vision Cues = Vision Input

• Allows perception of depth and distance 

Depth Perception: The ability to perceive 3 dimensional space and judge distance

Binocular Cues: Visual input from 2 eyes

Monocular Cues: Visual input from 1 eye

Perception

Perception:

• Perceptual organization

• Perceptual constancies

• Depth and Dimension

• Perceptual Set

• The World of Illusions

Perceptual Processing 

Bottom up processing: A, B, C, D..

• Begins at the bottom

• Raw sensory data is sent from the bottom up to the brain

• For higher processing

• Example: learning letters before learning words, then “reading”

Top Down Processing:

• Begins at the top

• The brain uses existing knowledge, beliefs, and expectations to interpret the sensory stimulation

• Example: can make sense when typos are not actual words

Gestalt Principles of Organization 

• Similarity- Objects that are alike are considered to be a unit

• Proximity- because of spacing objects considered a unit

• Closure- the tendency to fill in the gap to produce a familiar object

Identifying Objects 

Geons: (geometric icons) are simple 3D component shapes

• A limited number are stored in memory

• Geons are combined to identify essential contours of objects

Perceptual Constancies

Size Constancy: the tendency to view an object as a constant in size despite changes in the size of the object

Shape Constancy: The tendency to see an object as keeping its form despite changes in orientation

The Ames Room:

• A specially built room that makes people seem to change size as they move around in it

• The room is not a rectangle, as viewers assume it is

• A single peephole prevents using binocular depth cues

Depth and Dimension

The Visual Cliff

• Devised by Eleanor Gibson and Richard Walk to test depth perception in infants and animals

• Provides visual illusion of a cliff

• Caregiver stands across the gap

• Babies are not afraid to cross it until about the age they can crawl

The World of Illusions

The Müller-Lyer Illusion:

• Illusion in which the perceived length of a line is altered by the position of other lines that inclose it 

The Ponzo Illusion

• Illusion in which the perceive line length is affected by linear perspective cues

• Side lines seem to converge

• Top line seems farther away

Convergence (Binocular Cue)

• Turning eyes inward to fixate on the object

• To interpret distance as an object gets closer

Monocular Depth Cues

Relative Image Size:

• close objects cast a larger image than distant objects

• If two objects are roughly the same size, the object that looks the largest will be judged as being the closest to the observer

Texture Gradient:

• Nearby objects have a coarser, more distinct texture than distant ones

Linear Perspective:

• Parallel lines converge/move toward one another, as they recede/go into the distance

Aerial Perspective:

• Distant objects appear hazy and blurred

Parapsychology

Parapsychology:

• Psychology is the study of human behavior and mental processes 

• “Para” psychology means closely related to, or a departure from the normal

• The field of psychology that studies phenomenon that fall outside the normal realm of psychology

Extrasensory Perception (ESP)

• The ability to perceive something without ordinary sensory information

• This has not been scientifically demonstrated

Types of ESP:

• Telepathy: mind-to-mind communication

• Clairvoyance: perception of remote (far away) events

• Precognition: the ability to see future events before they happen