Chapter 4 - Sensation and Perception Flashcards
Define: Sensation
- Detection of physical energy by the sensory organs
- Raw “bottom-up” processing of info from outside world
Define: Transduction
The process of translating external stimuli into the “language of the brain”.
Define: Perception
- Brain’s stable and meaningful interpretations of the sensory organ input
- Higher order “top-down” processing that involves memory, previous experience, context, etc.
Define: Parallel processing
- We use a combination of both sensation and perception processes to experience “reality”
- Using many sense modalities simultaneously
Five common traits of transduction
- Specialized: Each sense has specialized cells
- Strength: Change in neuron firing rate depends on strength of stimuli
- Adaptation: Sensory adaptation; activation is greatest when stimulus first detected
- Organized: At each stage of processing sensory receptors are highly organized.
- Threshold
Define: Psychophysics
- A sub-field within sensation/perception area
- Researchers attempt to describe quantitatively the transition from stimulus to experience
- “General laws that apply for most people across all kinds of sensory input?”
- “How intense (bright, loud, hot) does a stimulus have to be in order to sense/perceive it” eg, how far can you see candle at night?
Define: Absolute Threshold
- The intensity level at which most people detect stimulus 50% of the time.
- Eg, candle flame at 48km; watch tick at 6m
Define: Just Noticeable Difference (JND)
Smallest detectable difference in magnitude between two stimuli that we can detect
Define: Weber’s Law
- Constant proportional relationship between the JND and original stimulus intensity
- The greater the stimulus, the greater the change in stimulus must be to perceive
- Eg, 500g sugar + 25g VS 50g + 25G
Per Weber’s law, change required for perception of change in weight, taste, tone, in %
Weight: 2%
Taste: 20%
Tone: 0.33%
Factors affecting individual’s response to JND
TEMPS
- Tired/alert
- Expectations (eg, perceptual sets)
- Motivation to detect
- Previous experience
- Strength of stimulus
Define: Signal Detection Theory (SDT)
- Noticing a stimulus against background “noise”
- Assessing potential gain/loss associated with your decision
- (ie, in response to intermittent very dim light: hit, false alarm, miss, correct rejection)
Define: Selective Attention
- Selecting one sensory channel and ignoring or minimizing others
- Rolse of RAS
Examples of selective attention
- Dichotic listening task (Donald Broadbent; tuning out different messages in each ear)
- Shadowing: mixing of two incomplete messages to form coherent whole
- Cocktail party effect: Hearing your own name
Define: Inattentional Blindness
Failure to perceive an event when our attention is directed elsewhere (gorilla basketball vid)
Three components of visual system (A,B,C)
- Visual Transduction (light enters eye, tansduced into neural messages)
- Extracting sensory messages from light (how eyes relay info to brain)
- Producing stable interpretations of visual input (identify objects, perceive motion, depth, perceptual constancies)
Define: Visible Light
400-700 nM part of electromagnetic spectrum
Define the two properties of light waves
Wavelength: Distance between crests of waves (corresponds to colour/hue)
Amplitude: Height of waves (corresponds to intensity/brightness)
Define basic parts of the eye
- Sclera: white
- Pupil: black middle
- Iris: colour; made up of muscles that constrict and dilate
- Cornea: bends light onto pupil
- Lens: contains muscles that change shape to focus, called accommodation.
- Retina: Lines inside back of eye; light sensitive, creating neural impulses; thin as onion skin
- Fovea: point of central focus; contains all of the cones
Some reasons pupil dilates
- “pupillary reflex”
- Doing something complex
- Finding someone attractive
Path taken by light
Cornea–pupil–lens–retina
Define: Blind spot
Where optic nerve connects to retina
No rods or sense receptors
Long & skinny lens can detect
Distant objects
Short & fat lens can detect
Close objects
Define: Myopia
Near-sightedness
Cornea too round or eyes too long (horizontally)
Define: Hyperopia
Far-sightedness
Cornea too flat or eyes too short (horizontally)
Define: Presbyopia
Lens loses elasticity as we age; loses ability to focus on close objects
How is image on retina oriented?
Upside down and reversed left to right
Describe: Cones
- Short and round
- 6 million on retina (fovea)
- Day-light vision
- Colour vision/fine detail/high spacial acuity
- Packed in fovea
Describe: Rods
- Slender and cylindrical
- 120 million on retina
- Dim-light vision (night)
- Shades of grey/low spatial acuity
- None in fovea
Define: Rhodopsin
- Photo pigments in rods
- Gets bleached; takes 20-30 min to re-sensitize
- In green leafy veg, some in carrots
Define: two theories of how we perceive colour
- Trichromatic Theory:
- Young-Helmholtz
- Three types of cones, each sensitive to red, green, or blue - Opponent Process Theory:
- Three types of cones sensitive to complimentary colours
- yellow/blue; red/green; black/white
Define: bottom-up processing
Perception controlled by physical messages delivered to the senses; whole is constructed from parts
Define: top-down processing
Perception controlled by one’s beliefs, experiences, expectations; imposed on raw stimulus
Define: Gestalt Principles of Visual Organization
-Rules governing how we perceive objects within their overall context
Define following monocular depth cues: Motion Parallax Interposition Light & Shadow Relative Size Texture Gradient Height in Plane Linear Perspective
Distant objects move slower; closer move faster
Closer object blocks view of object behind
Object cast shadow, showing 3D form
Distant objects look smaller
Distant objects have less apparent texture
Distant objects appear higher
Outlines of rooms/objects appear to converge in distance
Define: Monocular Depth Clues
Require input from only one eye
Define following binocular depth clues:
Binocular disparity
Convergence
Difference between location of images in each retina
How far the eyes turn inward to focus on moving object
What is the human audible range?
20 - 20,000 Hz
Define: Pitch (perceptually)
Frequency of wave (in Hz)
Short wavelength = more vib/sec = higher pitch
Define: Loudness (perceptually)
Amplitude of wave (in dB)
Whisper = 30 dB; normal convo = 60 dB; gunshot = 12- dB
Define: Timbre (perceptually)
Pattern of sound
Differentiates two sounds with same pitch and loudness
Define: Outer ear
- Pinna (visible part)
- Ear canal: funnels sound to tympanic membrane
Define: Middle ear
-Ossicles: Bones that vibrate and amplify frequency of soundwaves; link and transmit from ear drum to inner ear:
- Malleus (Hammer)
- Incus (Anvil)
- Stapes (Stirrup)
Define: Inner ear
- Cochlea: converts vibration into neural activity (snail shaped, fluid filled organ containing basilian membrane)
- Movement of fluid moves basilar membrane and organ of corti that contain hair cells
- Hairs are pushed/pulled by motion of fluid and convert acoustic information into action potential which travels down auditory nerve into brain
Explain inner ear and balance
- Semicircular canal filled with fluid and half circular canals, sense equilibrium, maintain balance, and detect:
- Gravity, change of speed, linear movement
Define: Monaural cues
Help distinguish sounds by one ear
Define: Binaural cues
Localize sound cues
