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