Sensation and Perception Flashcards
Synesthesia
The “crossing” of the senses, senses are connected
e.g. 6 is a number that is green
The nervous system is connected to the environment through…
The senses (sensory systems)
Purpose of the nervous system being connected to the environment
To guide behaviour (approach/avoid), specific for survival and reproduction
Sensation
Detecting external events by sense organs and turning it into neural signals (basic)
Perception
Organizing sensory info in the brain for a meaningful interpretation (more complex), tied to thought and memory
Sensory Psychologists study relationships between…
- Physical Stimulus, 2. Physiological Response and 3. Sensory Experience
Physical Stimulus
The matter or energy in the world
Physiological Response
Pattern of chemical and electrical activity in sense organs and CNS in response to Physical Stimulus
Sensory Experience
The subjective psychological sensation (perception)
5 Major Senses
Taste, Touch, Hearing, Vision, Smell
Sense of Smell
Molecules dissolved in fluid on mucous membranes in the nose trigger a response in the sensitive ends of olfactory neurons in olfactory epithelium in the nose
Sense of Taste
Molecules dissolved in fluid on the tongue trigger a response in the taste cells that are within taste buds on the tongue
Sense of Touch
Pressure on the skin triggers sensitive ends of touch neurons in skin
Sense of Pain
Potentially harmful stimuli triggers sensitive ends of pain neurons in skin and other tissues
Sense of Hearing
Sound waves are sensed by pressure-sensitive hair cells in cochlea of inner ear
Sense of Vision
Light waves are sensed by light sensitive rods and cones in retina of the eye
Steps of message getting to brain
- Stimulation of sensory receptors (Reception)
- Initiate neural impulses to sensory neurons - Physical/chemical stimulation converted into nerve impulse (TRANSDUCTION)
- Message arriving in the brain (sent to many different parts of the brain, including specific sensory areas of cortex.
Sensory Coding
Senses preserve relevant information in step 2, interpreted in step 3
Qualitative variation
Perceived as a precise type of energy
e.g. lights of different wavelengths (perceived as different colours)
Quantitative variation
Interpreted as an intensity, e.g. a sound or light can be weak or strong
Sensory Adaptation
The reduction of activity in sensory receptors with repeated stimulus exposure
- Change in sensitivity when receptors are consistently stimulated or unstimulated
e.g. turning off the lights at night, rods were understimulated, become extra sensitive
Stimulus Thresholds
How loud does someone need to whisper for you to hear it? etc.
Absolute threshold
Measures sensitivity
- Faintest detectable stimulus
- Varies from person to person
- Weakest amount can detect 50% of the time
- Get higher with age
William Fechner
One of the first psychophysicists
Psychophysics
How physical energy relates to psychological experience
Difference Threshold
Depends on magnitude of original stimulus
- Just noticeable difference
- Varies according to Weber’s law
Weber’s Law
JND changes as a proportion of stimuli
Signal Detection Theory
Stimuli is processed with previous experience and other senses
- integrated wholes
What is the purpose of human vision?
Identifying meaningful objects and movements
- Visual system has sorted all points and gradations in the reflected light into useful pieces through problems solving
Gestalt Psychology
We perceive whole, organized patterns rather than parts
- The organization of the parts, not the parts themselves
What does “Gestalt” mean?
Means “form” or “whole” in German
Form Perception
We automatically divide the visual scene into two parts (1. figure, 2. background)
Gestalt Grouping Principles
Proximity, Similarity, Connectedness, Closure, Illusory Contours
Transduction
Conversion of stimulus energy to electrical energy
Conservative Response Bias
Lots of misses and no
Liberal Response Bias
Lots of yes and false alarms
Weber Fraction
Ratio of minimum change in magnitude of stimulus to overall magnitude of stimulus
Dark Adaptation
Adjustment of your eyes to a dark room
Perceptual Adaptation
Occurs in the brain, results in after affects (brain perceiving opposite of what it was exposed to)
Example: Waterfall illusion
Autism
Reduced sensory adaptation, hypersensitivity, harder to detect changes in environment
Echolocation
Animals use soundwaves to map out an area
ex. dolphins, bats, owls, etc.
What are the best smellers on land?
Bears are known to be the best smellers, 7x better than a bloodhound, 2000x better than a human
- Olfactory cortex is 5x larger than a human
What range of wavelengths of light can humans detect?
750nm to 390nm (visible light)
What is the Just-noticeable difference of light?
Approx 1nm
Wavelength of light
Hue of colour
Amplitude of light
Max height of wave, intensity of brightness of light
Spectral colours
Colours that are made of one or just a few wavelengths
Iris
Decreases/increases side of pupil
Lens
Bends light to focus image on retina (fovea)
Accommodation
Adjusting the lens to focus the image
Presbyopia
Lens gets less elastic as people get older, accommodation ability weakens
Visual Transduction occurs….
In the rods and cones of the eye
Myopia
Objects projected in front of fovea
Hyperopia
Objects projected behind fovea
Photoreceptor cells
Contain photopigments
Photopigments
Sensitive to specific wavelengths of light
What happens when light hits photoreceptors?
It causes a chemical change to the photopigments and they change shape, which alters ion flow through the photoreceptor cell and the ionic concentration generates electricity, which moves to bipolar cells/ganglion cells -> ACTION POTENTIAL
Rods
All have same photopigment, important for SENSITIVITY, many are connected to one ganglion cell, used for dark vision
Cones
Have one of three photopigments, specialized for acuity, one to one match with bipolar/ganglion cells
How many rods and cones are there?
120 million rods, 5 million cones
Fovea
Location where most cones are found, most sensitive part of retina
Foveation
Focusing different stimuli on fovea through moving eyes
Acuity
Sharpness or specifity of perception
Sensitivity
Ability to detect a stimulus
Cortical magnification factor
Regions that require more detail (finer discrimination) get more cortical space
Visual Agnosia
Vision without knowing
Hierarchical analysis
Levels of the brain create more complete representation of the environment
Optic Chiasm
Information from each optic nerve diverges (switches sides)
- Left side of retina to left hemisphere
Feature detectors
Detect basic features
- ex. edges, lines, angles, etc.
Visual Association cortex
Secondary visual cortices
Damage results in difficulty organizing details
Ventral visual pathway
Along temporal lobe, answers “what” questions, damage results in difficulty recognizing objects
Dorsal visual pathway
Along parietal lobe, “where” and “how” questions, damage results in difficulty understanding where it is and how to use
Focused attention
The way that the ventral and dorsal visual pathway communicate
Movement Perception
Occurs in Middle Temporal Cortex, part of Dorsal pathway
- Knowing where something is depends on how it is moving
- Responds to motion in specific directions
Akinetopsia
Unable to perceive motion
Phi Phenomenon
Separate lights or images flashing in rapid succession perceived as a fluid movement
Sound waves
Are made of air pressure waves
Frequency in sound
Results in pitch (Hz)
Amplitude in sound
Volume, measured in dB
Timbre
Quality of sound
- Multiple wavelengths of sound
Human auditory range
20 to 20000 Hz
Pinna
Outer ear, sound funnel
Ear canal
Enhances certain sound frequencies
Tympanic membrane
Also known as the eardrum, vibrates, is the boundary between outer and middle ear
Ossicles
Tiny bones in middle ear (hammer, anvil and stirrup), connects eardrum to oval window, amplifies vibrations
Oval Window
Boundary between middle and inner ear, connects to cochlea
Cochlea
Transducer of the ear, full of fluid.
Basilar membrane
Vibrates when fluid in cochlea moves, causes cilia to bend
Cilia
More than 10 000 in each ear, bending triggers nerve impulses
- Bending in one direction depolarizes, other hyperpolarizes
Auditory nerve
Transfers information from cilia to brainstem
Frequency Theory
- Brain uses frequency of hair cell firing to determine pitch
- Neural hair alternate firing to account for higher pitches
- Better explains lower pitches, doesn’t account for amplitude
Place Theory
- Discovered by Hermann von Helmholtz
- Different pitches come from different places along basilar membrane
- High: beginning
- Low: tip
Georg von Bekesy
Proved Place Theory using cadavers
Place-frequency map/ tonotopic organization
Areas on the basilar membrane and primary auditory cortex corresponds with the order of their frequencies
What is the timing difference between the two ears?
0.000027 seconds
How do humans localize sound?
Using the timing difference between two ears, and the sound barrier the head creates, also using visual feedback to assist.
