Chp 3 - Perception Flashcards
Psychophysics
the branch of psychology that deals with relationships between physical stimuli and mental phenomena
- stimulus detection
- stimulus discrimination
Stimulus Detection
- What can be sensed or perceived and what cannot be
- Involves determining sensory thresholds (i.e., the weakest stimulus that a person is capable of perceiving)
- Stimuli can be supraliminal or subliminal
Sensory threshold
the weakest stimulus that a person is capable of perceiving
Just-Noticeable Difference
(JND)
the smallest physical
change a person can detect
more than 50% of the time
Stimulus Discrimination
- Amount of difference necessary for a person to perceive the difference
- Just-Noticeable Difference
(JND)
Signal Detection Theory
Delineates differences among four potential outcomes
signal: present /absent
response: yes/ no
hit/miss/correct rejection/ false alarm
subliminal
Less than 50% can be detected
stimuli that are not perceived at the conscious level and thus are not detected are called subliminal
supraliminal
Stimuli that are perceived above the threshold and thus are detected at the level of consciousness
Symbolic distance effect
2 stimuli can be discriminated more quickly when they differ more on symbolic dimension
Semantic congruity effect
the condition in which a person’s decision is faster when the dimension being judged matches or is congruent with the implied dimension.
implied dimension is height for balloon, how high, = congruent
for yoyo, lowness and how low = congruent
Anatomy of the eye (8)
→ Iris
→ Pupil
→ Cornea
→ Lens
→ Retina
→ Fovea
→ Blind spot
→ Optic nerve
Sensation
registration by the sensory organ (eyes) of a physical stimuli from the environment
Perception
subjective interpretation of sensations by the brain
- Perception of vision is not in the eyes, it’s in the brain
lens
Take care rest of focus
Fine tuning image based on distance
Change shape to when needed
three layers of neurons of the retina
- rods and cones
- bipolar cells
- ganglion cells
What happens after light waves enter the eye?
- light waves enter the eye, are focused and inverted by the lens, and are projected onto the retina
- rods and cones are stimulated by light, beginning the process of vision. Patterns of neural firing from these cells pass on to a second layer, the bipolar cells.
- bipolar cells then collect the mesages and move them along to the ganglion cells
- axon of the ganglion cells converge at the rear of the eye, forming the bundle of fibre that makes up the optic nerve
- the optic nerve signal exits the eye and continues through various structures, eventually projecting to the visual cortex of the occipital lobe in the lower rear portion of the brain.
fovea
- Central portion of the retina and allows for acute and detailed vision
- Packed tightly with receptors known as cones
- Each cone in the fovea has a direct line to the brain which allows the registering of the exact location of input
optic nerve
- Axons of ganglion cells exit through the back of the eye and travel to the brain
- The point at which it leaves is called the blind spot
- It contains no receptors
blind spot
no rods or cones
Devoted to bundling of the axons in that nerve
ratio of photoreceptors
- rods outnumber cones by a ratio of 20:1 or greater in the retina
Rods
- More numerous than cones
- Sensitive to low levels of light (dim light)
- Used mainly for night vision
- One type of pigment only
Cones
- Highly responsive to bright light
- Specialized for colour and high visual acuity
- In the fovea only
- Three types of pigment
The Periphery of the Retina
- Greater number of receptors called rods
- Detailed vision is less in peripheral vision
- Allows for greater perception of much fainter light in peripheral vision
Photoceptors convert signals into _______ _______
electrical impulses
Photoreceptors
- Located at the back of the eye
- Respond to light
- Sends signals to other cells closer to the eye
4 types of photoreceptors
Bipolar cell
Horizontal cell
Amacrine cell
(Retinal) Ganglion cell
Bipolar cell
Receives input from photoreceptors
Horizontal cell
Links photoreceptors and bipolar cells
Amacrine cell
Links bipolar cells and ganglion cell
Retinal ganglion cell
Gives rise to the optic nerve
Vision in New born babies:
cones a bit diff: short and fat, less efficient in capturing colour and detail
- Are spread out around the whole retina
- 1 yo is like an adult
Explain bad vision in babies
Visible spectrum
- Visible light is a portion of the electromagnetic spectrum
- The perception of color depends on the wavelength of light
- Humans perceive wavelengths between 400-700 nanometers (nm)
Humans: most sensitive to shades of green
- Evolutionary useful to look for predators, seek food
e.g. Blue obj: absorbed all wavelengths that are not blue
Retino-Geniculo-Cortical-Pathway
Left and right LGN
Lateral Geniculate Nucleus (LGN) Contralateral processing, to the vision
Part of the thalamus:
- Specialized for visual perception
-Destination for most ganglion cell axons
-Sends axons to other parts of the thalamus and to the visual areas of the occipital cortex
Each side send sig contralateral/ ipsilateral
Primary Visual Cortex (V1)
Receives information from the lateral geniculate nucleus and is the area responsible for the first stage of visual processing
Damage to V1 show blindsight
- an ability to respond to visual stimuli that they report not seeing
The ventral stream
The ventral stream refers to the path that goes through temporal cortex
The “what” path
Specialized for identifying and recognizing objects
damage to ventral stream↔can’t identify objects (visual-form-agnosia)
The dorsal stream
The dorsal stream refers to the visual path in the parietal cortex
The “where” path
Important for spatial perception, vision for action
Damage to dorsal stream↔don’t know where an object is in space (optic ataxia)
Bottom-up processing
emphasizes basic components
of a stimulus so recognition is influenced by the pattern
of incoming information
Top-down processing
emphasizes prior knowledge and
expectations for recognition
Gestalt Psychology
Gestalt: word for configuration
Law of Pragnanz
Law of similarity
Law of Proximity
Law of Good Continuation
Law of Closure
Necker cube
2 shaded version, 2 possible ways to view
Law of Pragnanz
We will interpret things in the simplest manner possible
Like to simplify, as it helps relieve cognitive load
Law of similarity
Tend to see items similar as a singular unit,
e.g. we see 2 columns of circles and triangles, instead of thinking of 16 shapes
Law of Proximity
Perceive as singular unit when close to each other
Law of Good Continuation
Visual systems perceives continuation
Law of Closure
Don’t need a shape to be completely encloses to view a shape
Figure-Ground
- Ground extends behind the figure
- Border ownership: borders belong to figure
How do we view a scene?
How to decide what is in the foreground vs. Bg
- Contrast between light and dark
Audition
- sound waves being sensed
- Vibration-induced changes in pressure of molecules through a medium
The ear main structures (7)
→ Pinna*
→ Eardrum*
→ Malleus*
→ Incus*
→ Stapes*
→ Cochlea*
→ Basilar membrane
Organ of Corti
- Rests on top of the basilar membrane
- Contains ~16,000 “hair cells” that are responsible for sensory transduction
Transfer sounds from basilar membrane to auditory cortex
The middle ear when sounds come in:
Make eardrum vibrate for sounds, at the same frequency
When vibrates, initiate movements in the middle ear
3 bones
-Incus
-Malleus
-Stapes
Transfer the sound into inner ear
Where does sensory transduction occur?
The cochlea of the (inner) ear
Basilar membrane
Layers the cochlea, frequency specific
-Will stimulate specific spots acc to frequency
Every single part of the BM (b4 the sound to be stimulated) will be stimulated regardless, over time, higher pitched harder to hear due to them being in the outer loop of the cochlea
How does sensory transduction occur?
Basilar Membrane
- Sheet of tissue running the length of the cochlea
- Frequency of the wave will cause
- maximum displacement / movement in different parts of the basilar membrane!
- High frequencies near the thicker, narrower base, lower frequencies near the thinner, wider apex
Basic properties of sound waves
- frequency = pitch (Hz)
- amplitude = loudness (dB)
- waveform
Frequency (Hz)
Compression: peaks and the troph
If I have a 1000 wavelength in 1s = 1000hz
Higher pitch= more wavelengths per sec
Human Audition
e.g. ultrasounds we cannot hear
Anything lower (decible lvl) than our threshold, we can’t hear it
Our voices are the focal point for listening
Synesthesia
A set of experiences in which input
from one sensory system produces a conscious
experience not only in that sensory modality but
also in another.
* Projective Synesthesia
* Associative Synesthesia
Synesthesia tend to be related to ________
People with misophonia are affected emotionally by common sounds — usually those made by others, and usually ones that other people don’t pay attention to. The examples above (breathing, yawning, or chewing) create a fight-or-flight response that triggers anger and a desire to escape.
Grapheme-Color Synesthesia
- see indiv letters as colour
- Only goes in one direction, e.g 9 is orange, but orange doesn’t remind them of 9
- More common in women than men
Visual Search
Synesthetes show response time profiles that are consistent with “pop out” color effects - Some do better on memory tests, as mem is mostly association
Associative Synesthesia
Feeling of connection, e.g. might hear the violin, connects to the colour yellow, but can’t see it
e.g cello sounds blue
Projective Synesthesia
Tend to think of, e.g. see particular colours when one modality is stimulated
Cross-modal Perception
e.g. at the movies, the audio comes from the speakers, but the visual info makes the sounds look like it comes from the screen
e.g. lipsyncing
How does the gesture of the marimba player affect the perception of the length of a note?
People to judge the length of the notes played without seeing it (think all the notes are the same length)
VS. Seeing: long gestures/short, length perceived as longer/ shorter, although it is still the same
Affordances
- The sense of action possibilities
inherent in what we perceive.
Each thing in the room makes us think of the action potential.
e.g see a chair, perceive as sth that affords me the opportunity to sit
e.g. for a small child, chair affords the opportunity to crawl under
Template
A model or pattern
- theories of pattern recognition, template is the pattern stored in memory agains which incoming stimuli are compared to recognise the incoming patterns
