Chapter 6: Sensation and Perception Flashcards
What is sensation?
The process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment…
aka the information the nervous system transmits to the brain.
What is perception?
The processes by which one’s brain organizes and interprets sensory input, enabling us to recognize meaningful objects and events.
In our everyday experiences, sensation and perception…
Blend into one continuous process.
What is bottom-up processing?
Starts at the sensory receptors, works up to higher levels of processing.
Sensory –> Integration of sensory information
What is top-down processing?
Constructs perceptions from the sensory input by drawing on our experience and expectations.
Processing guided by higher-level mental processes.
What three steps are basic to all our sensory systems?
- RECEIVE sensory stimulation –> Specialized receptor cells
- TRANSFORM stimulation –> Neural impulses
- DELIVER the neural information to our brain
What is transduction?
The process of converting one form of energy into another that our brain can use.
What is psychophysics?
The study of the relationships between the physical energy we can detect and its effects on our psychological experiences.
What are absolute thresholds?
The minimum stimulation necessary to detect a particular stimulus 50% of the time
=Half the time, you can detect, half the time, you cannot detect.
What is signal detection theory?
Prediction of how/when we will detect weak signals in the presence of background stimulation, as detecting weak stimulus depends on both strength and psychological state - experience, expectations, motivations, stress.
Why do people respond differently to the same stimuli? Why do reactions vary as circumstances change?
What are subliminal stimuli?
Stimuli you cannot detect 50% of the time - below your absolute threshold for conscious awareness.
What is priming?
The activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory, or response.
When can we evaluate a stimulus?
Even when we aren’t aware of it, and unaware of our evaluation.
What is the dual-track mind, in terms of sensation and perception?
Much of our information processing occurs automatically, out of sight, off the radar screen of our conscious mind.
What is the difference threshold?
The minimum difference between two stimuli required for detection 50% of the time. We experience the difference threshold as a ‘just noticeable difference’.
The difference threshold _________ with the size of the stimulus.
Increases
Does subliminal sensation enable subliminal persuasion?
Subliminal = Below consciousness
Though subliminal sensation can subtly influence people, they don’t have a powerful, enduring effect.
What is Weber’s law?
For an average person to perceive a difference, two stimuli must differ by a constant minimum PERCENTAGE, no a constant amount.
The proportion varies depending on the stimulus.
What is sensory adaptation?
When constantly exposed to an unchanging stimulus, we become less aware of it – our nerve cells fire less frequently = Less sensitive
How does the sensory adaptation not apply to vision?
Our eyes are always moving, whether we are aware of it or not! This ensures that the stimulation on the eyes’ receptors continually changes.
What is the pro to sensory adaptation?
It allows us to focus on informative changes in our environment, without being distracted by background chatter –> USEFULNESS
What is a perceptual set?
A set of mental tendencies and assumptions that affect, top-down, our sensations.
Expectations that come with experience.
What determines our perceptual set?
Through experience, we form concepts/schemas that organize and interpret unfamiliar information.
How does the immediate context affect our perception?
The context creates an expectation that, top-down, influences our perception.
How are perceptions influenced by our emotions and motivation?
Depending on how we feel and what our needs are at that moment, we perceive things differently.
This also alters our social perceptions.
How do we see?
Our eyes receive light energy and transduce (transform) it into neural messages that our brain processes, into what we see consciously.
What do we see as visible light?
A thin slice of the whole spectrum of electromagnetic energy.
What two physical characteristics of light help determine our sensory experience?
- WAVELENGTH: The distance from one wave peak to the next, determining its HUE (colour we experience) and its FREQUENCY (number of complete wavelengths in a given time).
- INTENSITY: Amount of energy in light waves, determined by the wave’s amplitude, influencing BRIGHTNESS.
A great amplitude = bright colours;
A small amplitude = dull colours.
How does the eye work?
- Light enters through the cornea
- The cornea bends light to help provide focus
- Light passes through the pupil: small adjustable opening
- The iris surrounds the pupil and controls its size (dilates/constricts), in response to light intensity and to cognitive & emotional states
- The lens, behind the pupil, focuses incoming light rays into an image on the retina - multilayered tissue on the eyeball’s sensitive inner surface.
- The lens focuses the rays, by changing its own curvature and thickness in a process called accommodation.
How come the image on the retina appears upside down and reversed?
Light rays reflected from the object pass through the cornea, pupil, lens.
The curvature and thickness of the lens change, to bring nearby/distant objects into focus on the retina.
Rays from the top of the object strike the bottom of the retina;
rays from the left side of the object strike the right side of the retina.
What is the pupil?
The adjustable opening in the center of the eye, through which light enters.
What is the iris?
A ring of muscle tissue that forms the coloured portion of the eye around the pupil and controls the size of the pupil opening.
What is the lens?
The transparent structure behind the pupil which changes shape to help focus images on the retina.
What is the retina?
The light-sensitive inner surface of the eye, containing the receptor rods & cones, plus layers of neurons that begin the processing of visual information.
What is accommodation?
The process by which the eye’s lens changes shape, to focus near/far objects on the retina.
How does retinal processing work?
- Light entering the eye triggers a chemical reaction in the rods and the cones at the back of the retina.
- The chemical reaction activates bipolar cells.
- Bipolar cells activate ganglion cells, whose combined axons form the optic nerve.
The optic nerve transmits information, via the thalamus, to the brain.
What are rods?
Retinal receptors that detect black, white, and gray. They are necessary for peripheral and twilight vision when cones don’t respond.
What are cones?
Retinal receptor cells concentrated near the centre of the retina, and function in daylight/well-lit conditions.
The cones detect fine detail and give rise to colour sensations.
What is the optic nerve?
The nerve carrying neural impulses from the eye to the brain = Information highway.
The thalamus is ready to distribute the information it receives from your eyes.
What is the blind spot?
The point at which the optic nerve leaves the eye, creating a “blind” spot because no receptor cells are located there.
How do rods and cones differ in where they’re found and what they do?
Cones cluster in/around the FOVEA: Retina’s area of central focus.
Each cone transmits its message to a single bipolar cell = “Personal hotline” = Direct connection, preserving the cones’ precise information = Better able to detect fine details.
Cones enable colour perception.
Rods share bipolar cells which send combined messages = Funnel their faint energy together.
Rods enable B/W vision, sensitive in dim light.
What is the Young-Helmholtz trichromatic (three-colour) theory?
The theory that the retina contains three different colour receptors, one most sensitive to red/green/blue, which, when stimulated in combination, can produce the perception of any colour.
What do colour-deficient people lack?
Functioning red or green-sensitive cones, or sometimes both.
What is the afterimage effect?
When we stare at a colour, then look at a white sheet of paper, we see its opponent colour.
What is Hering’s opponent-process theory?
There exist three sets of opponent retinal processes, red-green, yellow-blue, white-black, which enable colour vision.
Some cells are stimulated by green, inhibited by red, and vice-versa.
How does colour-processing occur?
In two stages…
- The retina’s red, green, and blue cones respond in varying degrees to different colour stimuli, as the Young-Helmholtz trichromatic theory suggested.
- The cones’ responses are processed by opponent-process cells, as Hering’s theory proposed.
