The Mind (Sensation and Perception) Flashcards
What is Sensation and Perception?
Our bodies are bombarded with information both when we’re
awake and asleep
Sensation: The process of detecting environmental stimuli or stimuli arising from the body
* Sensory systems have developed through natural selection to provide information that enhances survival within a particular niche (humans, dugs, and horses all have unique sensory systems)
* Differences in sensation occur from person to person (ie the need to wear corrective glasses of not), but are relatively subtle
Perception: The process of interpreting sensory information
* Individual differences become more evident: stimulation can be the same and sensation will be similar but interpretation is subjective
so perception is different
- Our sensory systems are particularly sensitive to change
What is the process of sensation? + aspects
- Begins with the interaction between a physical stimulus and our biological sensory systems
Stimulus: Anything that can elicit a reaction from our sensory
systems
Transduction: The translation of incoming sensory information
into neural signals which are sent to the brain
What is the process of perception? + aspects
- The brain constructs perceptions from sensory information (in the
form of neural signals) - Perception allows us to organize, recognize, and use the
information provided by the senses - Important gateway to perception is attention
Sensory adaptation: The tendency to pay less attention to a non changing source of stimulation
* Unfamiliar, changing, or high-intensity stimuli often affect our surroundings / have consequences for our safety, so they have a high priority for attention
Selective attention: Prioritize input to focus on a subset of
available information and exclude the rest
* Can’t process all stimulus
Bottom-up processing: Brain’s use of incoming signals to
construct perceptions
* Build simple input into more complex perceptions
Top-down processing: Impose a structure on the incoming
information
* Memories, other cognitive processes, and knowledge gained from prior experience interpret sensory information
All you hvae to do to mkae a snetnece raedalbe is to mkae srue taht the fisrt and Isat letrtes of ecah wrod saty the smae
** Bottom-up processing brings sensations of letter shapes to brain
* Top-down processing allows us to recognize individual words drawing on knowledge and experience
What are the thresholds? Who studied it?
- Gustav Fechner (1801-1887) developed methods which he called psychophysics for studying the relationship between the physical qualities of stimuli and the subjective responses they produce
Absolute threshold: The smallest amount of stimulus that can be
detected
Difference threshold: The smallest detectable difference between two stimuli
What is signal detection? Example?
Signal detection: The analysis of sensory and decision-making
processes in the detection of faint uncertain stimuli
* Two-step process: (a) the actual intensity of the stimulus, (b) the observer’s criteria for deciding whether the stimulus occurred
Case: driving fast on the highway
* A person more concerned about correctly identifying patrol cars (maximizing hits) might use more lenient standards for identifying patrol cars and slow down frequently (false alarms), but would get few tickets
* Another person might use stricter criteria for identifying a patrol car: they would have fewer false alarms but would run the risk of missing real patrol cars (maximizing misses)
What is Vision?
Vision: The sense that allows us to process reflected light
- Approx. 50% of our cerebral cortex processes visual information (3% for hearing, 11% for touch and pain)
- Human vision involves only a small part of the light spectrum
- gamma rays, x-rays, ultraviolet rays, infrared rays, microwaves, and
radio waves lie outside the capacities of the human eye
- gamma rays, x-rays, ultraviolet rays, infrared rays, microwaves, and
The Visual Stimulus - visible light, or the energy within the
electromagnetic spectrum to which our visual systems respond, is a type of radiation emitted by the Sun, other stars, and artificial sources such as a lightbulb
The Biology of Vision
- Begins in the eye
Cornea: The clear surface at the front of the eye that begins the
process of directing / bending light into the retina
Pupil: An opening formed by the iris
Iris: The brightly coloured circular muscle surrounding the pupil
of the eye
* Adjusts the opening of the pupil in response to the amount of light in the environment and to signals from the autonomic nervous system
Lens: The clear structure behind the pupil that bends light
towards the retina
* Muscles change the shape of the lens, allowing for accommodation: adjust our focus to see near or distant objects
Retina: Layers of visual processing cells (rods and cones) in the back of the eye that transduce light information
Fovea: An area of the retina that is specialized for highly
detailed vision
* Responsible for central vision
* Image of object that we stare directly at is projected onto fovea
Rod: A photoreceptor specialized to detect dim light
* More common as we move from the fovea to the periphery of the
retina —»peripheral vision (ability to see objects to the side while
looking straight ahead) views dim light better than central vision
* Don’t provide information about colour, nor do they provide clear, sharp images
* Human eye contains about 90 million rods
Cone: A photoreceptor in the retina that processes colour and
fine detail
* Function best under sharp bright light
* Human eye contains between 4 million and 5 million cones
Aspects of Visual Pathways
Blind spot: Optic nerve exit with no rods or cones
- Unaware of our blind spots because perception fills in the missing details
Optic nerve: The nerve exiting the retina of the eye
* Cross at the optic chiasm where the axons closest to the nose cross over to the other hemisphere while the axons on the outside proceed
to the same hemisphere
* Partial crossing —> everything to the left of centre in the visual field is processed by the right hemisphere while everything to the right of centre is processed by the left hemisphere
* To actually see something requires the brain to interpret the
information gathered by the eyes
What are the theories of Colour Vision?
Trichromatic theory: Theory of colour vision based on the existence of different types of cones for detection of short (blue), medium (green), and long (red) wavelengths
* Supported by observations of three primary colours of light
* Explained colour deficiency
* Cannot explain colour afterimages (staring at a colour for a long time and then seeing that colour elsewhere)
Opponent process theory: Theory of colour vision that suggests we have a red-green colour channel and a blue-yellow colour channel in which activation of one colour in each pair inhibits the
other colour
* Most people have 3 types of cones
* Very rare for individuals to have either one type of cone or none —> sees world in black and white
* People who have two types of cones are colour blind
What are the ways to organize incoming sensory information?
(Gesalt Psychology)
Organization principle: We analyse visual input by dividing a scene into figure and ground —> we identify the main object in the scene
Proximity principle: Objects that are close together tend to be grouped together
Continuity principle: We assume that points which form smooth lines when connected belong together
Closure principle: We “fill in the blanks” when we see an image made of lines or gaps
Simplicity principle: We will use the simplest solution to a perceptual problem
What are the aspects of Depth?
Depth perception: The ability to use the 2D image projected onto the retina to perceive 3D
* Use monocular and binocular cues
Monocular cue: Depth cue that requires the use of only one eye
* Texture gradients and shading
* Occlusion: The blocking of images of distant objects by closer objects
* Illusions as well fmm our environment also result from our use of monocular cues to judge depth (eg. different backgrounds)
Binocular cue: depth cue that requires the use of both eyes
* Our most effective depth cue is retinal disparity: difference between images projected onto each eye
* Provides information of the relative distance between two objects in the visual field (as distance between objects increases, disparity increases)
* Helps predators when hunting prey camouflage
* Retinal disparity allows them to spot tiny variations in depths of objects in the visual field
Define and what does it allow us to do? What is sound?
What is Audition?
Audition: Sense of hearing
* Allows us to identify objects and communicate with others through language
* Sound is the movement of an object that sends vibrations in the form of waves in varying amplitudes and wavelengths
Name. (Outer, middle, inner, nerves).
Parts of the Ear
OUTER EAR
Pinna: Collects and focuses sound and also helps us localize sounds as being abovenoelow the head
* Auditory canal
* Tympanic membrane: Also known as the eardrum
MIDDLE EAR
Oval window: Boundary between outer and middle ear
Tiny bones: Transfers sound energy from air of outer and middle ear to fluid found in inner ear
INNER EAR
Cochlea: Structure in the inner ear that contains auditory receptors
* Has three chambers that are separated by membranes
* Two chambers: Vestibular canal and the Tympanic canal
* Sound waves produced in the fluid of the vestibular canal travels around the apex and back through the tympanic canal
Cochlear duct: lies between vestibular and tympanic canals separated by the basilar membrane
Basilar membrane: membrane in the cochlea on which the Organ of Corti is located
* Organ of Corti: Rests on top of the basilar membrane and contains auditory receptors
* Hair cells that transduce sound energy into neural signals
Auditory nerve: Nerve carrying sound information from the cochlea to the brain
* One branch of the auditory nerve cell makes contact with hair cells
* Second branch proceeds to medulla of the brainstem
Medulla —> Midbrain (manages reflexive response to sound) —> Thalamus —> Primary Auditory Cortex (analyzes sound) —> Secondary Auditory Cortex (responds to complex stimuli)
Tones and movement
Pitch Perception
High frequency tones produce maximum movement of the base basilar membrane
Low frequency tones produce maximum movement near apex of basilar membrane
Relationship between frequency + perception + loudness.
(Max sounds)
Loudness Perception
Frequency of sound interacts with our perception of its loudness
We can hear with maximum sensitivity sounds between 80 Hz - I0 000 Hz
