Sensation and Perception: In-Class Flashcards
What is bottom-up processing (vs top-down processing)?
SENSATION –> PERCEPTION
Stimulus –> Transduction –> Receptor cells –> Neural processing in the PNS, spinal cord, brain stem –> Thalamus –> Neural processing in the brain –> Percept
What is the signal detection theory? What does perception depend on?
The presence of a stimulus does not indicate the presence of a percept (detection).
The perception/detection of a stimulus depends on…
- Presence of (target) stimulus
- Presence of noise
- Sensitivity to stimulus
- Cognitive factors, top-down processing
What is an individual’s absolute threshold?
The intensity of the stimulus at which the detection rate is at least 50%.
What is the stimulus/percept matrix?
Stimulus present, percept present: Hit
Stimulus present, percept absent: Miss
Stimulus absent, percept present: False alarm
Stimulus absent, percept absent: Correct rejection
What is an individual’s difference threshold (JND)?
The minimum difference between two stimuli, for a rate of detection of at least 50%.
Difference in the DENSITY of the stimulus.
What is Weber’s law?
K = Delta I (noticeable difference) / I (starting intensity)
Where…
K = Weber Fraction
I = Intensity of the stimulus
The difference threshold is proportional to the intensity of the stimulus.
What is sensory adaptation?
Reduced sensory sensitivity to a stimulus, after prolonged exposure.
This occurs both at the receptor level as well as in the cortex, therefore applying to bottom-up and top-down processing.
What is perceptual priming?
In top-down processing, the phenomenon in which later perceptions are affected by earlier exposure to similar stimuli. Occurs at the cortical level.
Top-down processing: Perceptual set
Tendency to perceive stimuli in a particular way, as determined by the schemas that come to bear on the current stimulus.
What factors affect our perceptual set?
- Previous exposure to another stimulus, aka priming
- Current context
- Internal psychological state: Expectations, emotions, motivation
- Prior knowledge and experience
- Culture
What are photoreceptors comprised of?
RODS (95%)
- Very sensitive to light
- Monochromatic: Sensitive to black, white, gray
- Enable scotopic (low-light) vision
- Enable peripheral vision
CONES (5%)
- Highly concentrated in the fovea
- Sensitive to colour and detail
- Used in bright-light settings
- Three types = Red, green, blue
What is the vertical visual pathway?
What is the horizontal visual pathway?
Rods + cones –> Bipolar cells –> Ganglion cells –> Optic chiasm –> Thamalus –> Primary visual cortex
Rods –> Bipolar cells
Cones –> 1 bipolar cell
What is Young-Helmholtz’s Trichromatic Theory?
We perceive a wide range of colours as a result of varying combinations of red, green, and blue cones being activated.
What the Opponent-Process Theory?
We perceive colour as a result of three pairs of opposing processes:
- Red/green
- Blue/yellow
- Black/white (luminance)
What is one of the visual cortex’s functions?
It gives rise to more complex FEATURE DETECTORS,
cells that are specialized to movement, location, structure, receptive fields, roles = Localization of function
What is the concept of parallel distributed processing?
The idea that there is shared specialization, within which each area responds MORE to one thing, while still being able to detect the others.
What is the Gestalt theory?
The idea that the percept is more than the sum of the sensations themselves; we always perceive in CONTEXT, which gives rise to our interpretation.
What are the Gestalt principles of perceptual constancy?
Shape constancy: The form does NOT change with perspective.
Size constancy: Size does not change with distance.
Colour constancy: Colour does not change with illumination/lighting
Brightness constancy: Brightness does not change with illumination/lighting
What are the two aspects of sound waves?
Wavelength = Sound pitch = Place theory (high-frequency sounds) and Frequency theory (low-frequency sounds)
Wave amplitude = Sound loudness = Number of hair cells responding
In audition, what is the principle of localization?
The differences in intensity and timing of sound between the two ears.
What is the auditory pathway?
Hair cells –> Thre consecutive nuclei in the brainstem –> thamalus –> primary auditory cortex
What is the vestibular sense?
The perception of position, movement, and balance of the whole body. This can be traced back to the inner ear!
What is the role of the semicircular canals?
- ANTERIOR: Tilting back-and-forth movement
- POSTERIOR: Tilting side-to-side movement
- LATERAL: Swiveling, horizontal movement
What is the role of vestibular sacs?
These otolithic organs sense head position and acceleration to movement –> Respond to gravity
What are the four types of somatosensation receptors?
- Mechanoreceptors: Pressure
- Thermoreceptore: Hot and Cold
- Nociceptors: Pain
What is the pathway of touch?
Mechanoreceptors –> Up the spinal cord –> Medulla –> Decussate –> Thalamus –> Postcentral gyrus
What is the pathway of pain?
Nociceptors –> Spinal cord –> Decussate –> Thalamus –> Postcentral gyrus
What is the gate control theory?
The idea that we can lessen pain signals by incorporating other sensations. The pain signals can be interrupted in the substantial gelatinase of the spinal cord, which acts as a gate.
What is the principle of multi-sensory integration?
Some people rely on certain senses more than others!
