Chapter 4 Flashcards
Sensation
- the stimulation of the sense organs
- detection of physical energy by sense organs, which then send information to the brain
Perception
- the selection, organization, identification and interpretation of sensory input, in order to form a mental representation
- the brain’s interpretation of raw sensory inputs
Transduction
- a process in which the sensors in the body convert physical signals from the environment into encoded neural signals sent to the CNS
- a process of converting an external energy or substance into electrical activity within neurons
Sensory adaptation
- a gradual decline in sensitivity due to prolonged stimulation
- a process in which activation is greatest when a stimulus is first detected
Psychophysics
- the study of quantitative relations between psychological events and physical events or, more specifically, between sensations and the stimuli that produce them
Absolute threshold
The lowest level of a stimulus needed to detect a change 50% of the time
Just noticeable difference
Smallest change in intensity of a stimulus that one can detect
Weber’s Law
The change in a stimulus that will be just noticeable is a constant ratio of the original stimulus
Fechner’s Law
Describes the relationship between stimulus magnitude and perceived magnitude. The magnitude of perceived intensity increases proportionally to the logarithm of the stimulus intensity
Steven’s Law
- An empirical relationship between an increased intensity or strength in a physical stimulus and the perceived magnitude increase in the sensation created by the stimulus
- Basically, it’s an equation/law that expresses the fact that our perception of how much the stimulus has increased is not the same as how much the stimulus has actually increased
- After a certain point, increasing the strength of the electric shock by just a little bit makes us perceive a much stronger electric shock– we think that the magnitude of the shock has increased by a lot more than it really has!
- After a certain point, we need to increase brightness by a lot to perceive a difference in the magnitude of brightness (opposite trend from the electric shock)
Bottom up processing
Begins with perception of raw stimuli and ends with our synthesizing them into a meaningful concept
Top down processing
Begins with beliefs and expectations which are imposed onto raw stimuli
Iris
Coloured ring of muscle surrounding the pupil, which helps regulate the amount of light passing into the eye
Pupil
Hole through which light passes; size controlled by the iris
Sclera
The white part of the eyeball
Cornea
Curved, transparent layer covering the iris and pupil; bends incoming light to focus the incoming visual image at the back of the eye
Lens
Part of the eye that changes curvature to keep images in focus; changes shape to allow us to see both distant objects and nearby objects
Retina
- Thin membrane at the back of the eye; contains two types of photoreceptor cells (rods/cones)
- Also consists of bipolar neurons and ganglion cells
- The photoreceptors convert light stimuli into electrical nerve impulses
- The nerve impulses are transmitted via bipolar neurons to ganglion cells
- The ganglion cells are apart of the optic nerve fibre, which then sends the electrical nerve impulses to the brain
Fovea
Central part of the retina; responsible for acuity; only contains cones
Acuity = sharpness of vision
Rods
One of two receptor cells found in the retina Much more plentiful than cones Long and narrow Allow us to see basic shapes/forms Good for nighttime and peripheral vision Monochromatic
Cones
One of two receptors cells found in the retina
Less abundant than rods
Shaped like cones
Good for daylight vision and colour vision
Three types, blue/green/red, that are sensitive to different wavelengths of light
Optic nerve
Transmits impulses from the retina to the rest of the brain
Optic disk/Blind spot
A hole in the retina where the optic nerve exits the eye; region of the retina containing no rods and completely devoid of sense receptors; the place where the optic nerve connects to the retina
Optic chiasm
Point at which the optic nerves from the inside half of each eye cross over and project to the opposite half of the brain
Ciliary body
Controls the shape of the lens
Eye muscle
Controls movement of the eye
Accomodation
changing the shape of the lens to focus on objects near or far; flat lens (long/skinny) allow us to see distant objects; fat lens (short/wide) allow us to see nearby objects
Pathway of light
Cornea Pupil Lens Retina (rods/cones → bipolar neuron → ganglion cell → optic nerve) Optic nerve Optic chiasm Visual cortex
Receptive Fields
A collection of rods and cones that funnel signals to a particular visual cell in the retina
When stimulated, this field affects the firing of the visual cell
There are two types of receptive fields: center-on (excitatory center) and center-off (inhibitory center)
Feature detectors
- neurons that respond selectively to very specific features of more complex stimuli
- two types: simple cells and complex cells
- Feature detector cells detect lines and edges
- Hubel and Wiesal found that some cells in the visual cortex fire in response to slits of a specific orientation/location (simple cells) while other cells fire in response to movement of slits in a specific direction/orientation (complex cells)
Simple cells
respond best to lines of correct width, orientation and location in receptive field
Complex cells
respond best to movement of lines in a specific direction
Trichromatic theory
Idea that colour vision is based on our sensitivity to three primary colours: blue, green and red
We have three types of cones that have different sensitivities to certain frequencies of light
Colours other than blue/green/red are a result of the additive mixing of light (combinations of blue/green/red)
Opponent process theory
Colour perception depends on receptors that make antagonistic responses to three pairs of colours: blue/yellow, green/red, and white/black
The presence of green inhibits red and vice-versa in that particular spot on the visual field; same with blue/yellow and white/black
Depth perception
- The interpretation of visual cues that indicate how near or far away objects are
- Appears in infancy
Monocular cues
- clues about distance based on the image in either eye alone
- includes motion parallax and pictorial depth cues
Motion parallax
- Monocular depth cues resulting from the images of objects at different distances moving across the retina at different rates
- Objects that are closer tend to move quicker than objects far away
Pictorial depth cues
- monocular clues about depth that can be given in a picture
1. Linear perspective: parallel lines converge in the distance
2. Texture gradients: closer objects have more texture detail than objects far away
3. Interposition: objects that have other objects in front of it tend to be further away
4. Relative size: determine distance by size; smaller = further away
5. Height in plane: objects lower in the plane tend to be closer, while objects higher tend to be further
6. Light and shadow: the presence/location of light and shadows help us to perceive depth
Binocular cues
- clues about distance based on the differing views of the two eyes
- includes retinal disparity and convergence
Retinal disparity
- binocular cue
- objects project images to slightly different areas in each eye
Convergence
- binocular cue
- sensing the eyes converging towards each other as they focus on closer objects
Illusion
perception in which the way we perceive a stimulus doesn’t match its physical reality
Perceptual constancy
the tendency to experience a stable perception despite continually changing sensory input
Distal stimuli
stimuli that lie in the distance (in the world outside the body)
Proximal stimuli
the stimulus energies that impinge directly on the sensory receptors
Perceptual hypothesis
an inference about which distal stimuli could be responsible for the proximal stimuli sensed
Shape constancy
the tendency to perceive the shape of a rigid object as constant despite differences in the viewing angle
Colour constancy
the tendency to perceive the colour of objects as constant despite differences in illumination conditions
Size constancy
the tendency to perceive the size of objects as constant despite the fact that the size of objects on the retina vary greatly with distance
Pinna
Flexible outer flap of the ear, which channels sound waves into the ear canal
Ear canal
Conducts sound waves to the eardrum
Eardrum
Membrane that vibrates in response to sound waves; separates the outer ear from the middle ear
Ossicles
- malleus, incus, stapes
- Tiny bones located just beyond the eardrum; vibrate at the frequency of the sound wave, transmitting it from the eardrum to the inner ear
Semicircular canals
Fluid-filled structures that play a role in balance
There is one for each plane (x, y, z) so three in total
Cochlea
Spiral shaped organ with a fluid-filled inner cavity; converts vibration into neural activity
Organ of Corti
Tissue in the cochlea containing the hair cells necessary for hearing
Basilar membrane
Membrane in the cochlea supporting the organ of Corti and hair cells
Pathway of sound
Pinna Ear canal Eardrum Ossicles (Malleus → Incus → Stapes) Cochlea Auditory nerve Auditory cortex
Frequency theory
The rate at which neuron fire action potential reproduces the pitch (up to 100 Hz)
Volley theory
Variation of frequency theory
Sets of neurons fire at their highest rate out of sync to reach rates up to 5000Hz
Place theory
Hair cells at the base of the basilar membrane are excited by high pitch, whereas hair cells at the top of the basilar membrane are excited by low pitch
Account only for high pitch tones (5000 to 20000)
Types of deafness
Conductive: due to malfunctioning of the ear (failure of the eardrum or the ossicles of the inner ear)
Nerve: due to damage to the auditory nerves
Olfaction
- smell
Odour interact with sense receptors in the nasal passage
Each olfactory neuron contains a single type of olfactory receptor, which recognizes an odorant on the basis of its shape
Each olfactory receptor recognizes a particular odorant; “lock-and-key” method
When olfactory receptors come into contact with odour molecules, action potentials in olfactory neurons are triggered
Info reach the olfactory cortex and part of the limbic system
Amygdala helps distinguish pleasant from disgusting smell
Gustation
- taste
Sensitive to five basic tastes
Sweet, salty, sour, bitter and umami
Perception biased by sense of smell
Info interact with taste bud, reach gustatory cortex and part of the limbic system
Person with damaged gustatory cortex don’t experience disgust
Tongue taste maps are a myth!
What’s the convergence site for smell/taste?
frontal cortex
Pheromones
Odorless chemicals serve as social signals to members of one’s species
Most mammals use vomeronasal organs to detect pheromones– Doesn’t develop in human
Touch vs Pain
- touch information travels faster than pain
- touch informs us of our immediate surroundings, and keys us to urgent matters
- pain alerts us to take care of injuries, which can often wait a little while
Pain
- an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. Personal subjective experience, influenced by cultural learning, the meaning of the situation, attention paid to the situation, and other psychological variables.
- Pain producing stimuli has a threshold: the point at which we perceive it as painful
Mechanoreceptor
- specialized nerve endings located on the ends of sensory nerves in the skin; sense touch, deep pressure and temperature
Free nerve endings
- more plentiful than specialized nerve endings
- also sense touch, temperature and especially pain
Nociceptors
- pain receptors
Four types: mechanical, thermal, chemical, polymodal
Mechanical nociceptor
respond to excess pressure or deformation or breaks in the skin
Thermal nociceptor
activated by different levels of temperature (hot/cold)
Chemical nociceptor
respond to a number of chemicals such as spices, venom, environmental irritants and endogenous chemicals that arise from changes in tissue
Polymodal nociceptor
senses more than one type of pain stimuli
Traditional theories of pain
Pain results from the transmission of pain signals from the site of injury to the brain
Amount of pain experienced is directly proportional to the amount of tissue damage
Gate Control Theory of pain
There is a “pain gate” that can open and close to modulate the experience of pain
Psychological factors play an important role
Interrelationships between pain, emotions and cognitions
Emotional factors of pain vs Cognitive factors of pain
- anxiety/worry/depression = emotional
- focusing on pain/boredom = cognitive
Functions of pain/pain expression
- protect organism from further harm
- alert co-species to possible harm
- recruit empathy and care from others (possibly)
Proprioception
- kinesthetic sense
- helps us keep track of where we are and move efficiently
- use proprioceptors to sense muscle stretch and force
- can tell what our bodies are doing, even with our eyes closed
- stretch receptors embedded in muscle and force detectors embedded in muscle tendons
- proprioceptive information enters the spinal cord and travels upward through the brainstem and thalamus to reach the somatosensory and motor cortexes
- there, our brains combine information from our muscles and tendons, along with a sense of our intentions, to obtain a perception of our body’s location
Vestibular sense
- our sense of equilibrium
- inner ear contains three semicircular canals, filled with fluid to help us sense equilibrium and maintain our balance
- vestibular information reaches parts of the brainstem that control eye muscles and triggers reflexes that coordinate eye and head movements
- vestibular information also reaches the cerebellum which controls bodily responses that enable us to catch our balance when we’re falling
- not heavily represented in our cerebral cortex, so our awareness of this sense is limited; only become aware of it when we lose our sense of balance or when there’s a dramatic mismatch between our vestibular and visual inputs (ie. moving in a car while not looking outside)
Gestalt principles
- Proximity: Objects physically close to each other tend to be perceived as unified wholes
- Similarity: All things being equal, we see similar objects as composing a whole, much more so than dissimilar objects. If red/yellow circles are lined up horizontally, we perceive separate rows of circles
- Continuity: We still perceive objects are wholes, even if other objects block part of them (ie. the cross)
- Closure: When partial visual information is present, our brains fill in what’s missing (ie. Kanza square)
- Symmetry: We perceive objects that are symmetrically arranged as wholes more often than those that aren’t
- Figure-ground: Perceptually, we make an instantaneous decision to focus attention on what we believe to be the central figure, and largely ignore what we believe to be the background
Face perception
- we have cells that fire in response to things that look like faces
- brains desire to see faces as faces
Phi phenomenon
- illusory perception of movement produced by the successive flashing of images
- our perception of what’s moving and what’s not are based on only partial information, with our brains guessing what is missing
Sound location perception
When the auditory nerve enters the brain stem, some of its axons connect with cells on the same side of the brain, but the rest cross over to the other side of the brain
Information from both ears reach the same structures in the brain stem
Since the two sources of information (ie. left ear/right ear) take different routes, they arrive at the brain stem slightly out of sync
There is also a difference in loudness between the two ears
Our brains compare the difference in loudness/timing (binaural cue) to determine the location of sound
We mostly rely on binaural cue to determine the source of sounds, but we also use monaural cues (one ear only) which helps us to distinguish sounds that are clear from those that are muffled
Subliminal perception
- perception below the limen, or threshold of conscious awareness
- supported by evidence
- when researchers subliminally trigger emotions by exposing subjects to words related to anger, the subjects are more likely to rate other people as hostile
- subliminally presenting religious words made participants less likely to cheat than those presented with non-religious words
Subliminal persuasion
- subthreshold influences over our decisions/votes in elections/product choices/etc.
- no evidence
- we don’t engage in much/any in-depth processing of the meaning of subliminal stimuli, so the stimuli probably cannot produce large-scale or enduring changes in our attitudes/decisions
- self-help tapes are ineffective
- reversed subliminal messages probably also do not influence behaviour
