Biological Psych - Sensation and perception Flashcards
Perception
Involves the processing, organization, and interpretation of sensory signals in the brain, which results in an internal representation of the stimuli - and your conscious experience of it
Sensation
Involves the detection of external stimuli (ex. light, pressure), responses to those stimuli, and the transmission of these responses to the brain
Transduction
Process by which sensory receptors pass impulses to connecting neurons when they receive stimulation (ex. pressure on the skin from touch)
Absolute threshold
The minimum intensity of stimulation that must occur before you experience a sensation (or the stimulus intensity detected above chance)
Difference threshold
The just noticeable difference between two stimuli (the minimum amount of change required for a person to detect a difference 50% of the time)
Taste
- Every taste experience is composed of a mix of five basic qualities (sweet, salty, sour, bitter, umami/savoury)
- Smell and texture are also important (remember the taste experience occurs in your brain)
Olfactory epithelium
A thin layer of tissue embedded with smell receptors, which transmit information to the olfactory bulb, which is the brain center for smell
Orbitofrontal cortex
- Receives info from smell, taste, and visual systems
- Flavour perception
Mechanoreceptors
- Respond to mechanical distortion or pressure
- The most sensitive mechanoreceptors are found in the cochlea (responsible for sound transduction)
The primary somatosensory cortex
- Connected parts of the body tend to be represented beside each other
-> Somatotopic organization - More sensitive regions tend to have more cortical area devoted to them (ex. lips, fingers)
-> Sensory homunculus
Myelinated fibers
“A delta”
Sharp, immediate pain (protection)
Lightly/non-myelinated fibers
“C”
Dull, steady pain (recuperation)
Gate control theory of pain
For pain to be experienced, pain receptors must be activated AND the neural “gate” in the spinal cord must allow the signals through to the brain
- If the gate is “open”, pain is experienced
- If the gate is “closed”, pain is reduced/prevented
Accomodation
Muscles change the shape of the lens, flattening it to focus on distant objects, and thickening it to focus on closer objects
Photoreceptors
Convert the energy from light particles (photons) into a chemical reaction that produces an electrical signal
Rods
Retinal cells that respond to low levels of light, and result in black and white perception. About 120million in each retina, located along the edges.
Cones
Retinal cells that respond to higher levels of light, and result in color perception. About 6million in each retina, located in the fovea.
Types of cones
- According to the trichromatic theory, the perception of colour is determined by the ratio of activity among these three types of receptors
□ S cones -> short wavelengths -> blues
□ M cones -> medium wavelengths -> greens
□ L cones -> long wavelengths -> reds
Opponent-process theory
- Hering 1920
- Focus on ganglion cells in the retina
- Three opposing pairs (if one colour in the pair is stimulated, the other is inhibited)
-> Red/green
-> Yellow/blue
-> White/black
Motion sensitive neurons
Fatigue of certain motion sensitive neurons leads to motion after-effects (the waterfall illusion)
Visual transmission
Rods and cones -> bipolar, amacrine, horizontal cells -> ganglion cells/optic nerve -> thalamus (LGN) -> primary visual cortex
Dorsal stream
“where”
Specialized for spatial perception, determining where an object is and its spatial relation to other objects
Ventral stream
“what”
Specialized for perception and recognition of objects, such as determining color and shape
Gestalt principles of perceptual organization
- Figure-ground relationship
- Illusory contours
- Proximity
- Similarity
- Continuation
- Closure
Figure-ground relationship
Whatever is not the figure (the focus of visual field) is automatically assigned as background
Illusory contours
We tend to perceive contours, even when they don’t exist (but something in the stimulus suggests that they ought to be present)
Proximity
The closer two figures are, the more likely we are to group them together and see them as being part of the same object
Similarity
We tend to group figures according to how closely they resemble each other
Continuation
We tend to interpret intersecting lines as continuous rather than as changing direction radically
Closure
We tend to complete figures that have gaps
Retinal disparity
Important cue of depth perception, caused by the distance between the eyes, which provides each eye with a slightly different image. The brain uses the disparity between these two retinal images to compute distances.
Monocular depth cues
Include occlusion, relative size, familiar size, linear perspective, texture gradient, and position relative to horizon
Motion parallax
Objects that are farther away seem to move more slowly that objects that are closer
Bottom-up processing
Information is sent from lower-level processing areas to higher level processing areas
Top-down processing
Information from higher-level areas can also influence lower, “earlier” levels in the processing hierarchy
Hemisphere study
- Left hemisphere vocalizes a response, and it sees what is on the right side of the visual field
- Left hemisphere doesn’t know what the right hemisphere has seen (the rubber duck), so it interprets the left hand’s response (pointing to the bathtub) in a manner consistent with the knowledge it has
Interpreter
- A left-hemisphere process that attempts to make sense out of events
- Creates a comprehensible story out of events, provides a narrative, tries to find patterns, relationships
Fusiform face area
- Area of the brain that becomes particularly active when people look at faces (some evidence that it is an “expertise” area and not just for faces)
