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Unit 4: Sensation and Perception

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Laura Koritz

on 1 March 2017

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Transcript of Unit 4: Sensation and Perception

Sensation and Perception
Vision: Sensation
Sensing and perceiving things is very very important; the only way we can get information from our world.
Not much would be possible if we couldn't get information from our eyes, ears, nose, skin, mouth, etc. (Which would you give up?)
Vision is the sense we probably rely on most everyday.
sensation and perception are DIFFERENT Processes.

You can have one without the other!
We sense things all the time without perceiving them.

If all the sensory information we took in came into our conscious mind it would be difficult to function.
We can also sometimes perceive things that we don't really sense.

Most often in connection to abnormal psychology (e.g. schizophrenia), because our senses are pretty well designed.
Wavelength creates color:

rods - light sensing (black and white), great at catching movement, more on edges of retina
cones - color detection, many more in center of retina.

(Fovea is the direct center, optic nerve creates "blindspot")
Distal stimulus - the actual thing you're seeing.

Proximal stimulus - the image that hits your retina.
Vision: Perception
Perception happens in our brains, where the raw data from the environment, transmitted by our sense organs and neuron pathways, is created into a meaningful thing.
figure-ground relationship
Your brain can perceive the background and foreground. Requires PROCESSING of the raw information.
Depth Perception
Binocular Cues:

how different are the two images, (one from each eye)

where are your eyes turned? straight out vs turned in to some degree
Monocular Cues:

ways to tell depth using only one eye (or if things are further away and binocular cues don't work)
motion parallax - faster moving things are closer.
Linear Perspective
Relative Size: smaller ones seem further away
Texture Gradient: detailed textures are closer
Relative Clarity:
Further away = more blury
Muller-Lyer Illusion - Cultural influence on perception

"Capentered" cultures that use lots of right angles tend to get the sizes wrong. Cultures that don't tend to see that they're the same length.
How good are your perception powers? Which of these lines are longer?
Sight is based on detecting light energy, but hearing is detecting mechanical waves that travel through a medium (usually air).
Sound waves go in your outer ear, and cause your eardrum (tympanic membrane) to vibrate.

The vibrations go through three little bones, and to the cochlea (a small organ in the inner ear)
Small hairs inside the cochlea vibrate. The hairs are connected to nerves, which pass the information on to your brain.
Front of your head; light comes from this way.
Conduction Deafness - damage to the outer or middle ear stops the information from being detected
Sensorineural Deafness - damage to the inner ear, the cochlear nerve, or the auditory cortex stops the information from being detected, passed to the brain, or perceived
Other Senses:
Habituation: reduced attention to a stimulus over time as you are exposed to it a lot;

e.g. a sound in the background that you notice less and less

You'll be able to bring it back into your attention if you want to.
Dishabituation - When the stimulus changes you would notice it again.
Sensory Adaptation - senses respond less and less over time as your exposed to a stimulus (sensory cells actually fire less because the signal isn't changing)

e.g. eyes and saccades; if held in place on a fixed image, sight will fade.
Selective attention:

You can attend to some stimuli, and ignore others, even though these others will still enter your brain and be processed.

e.g. Cocktail Party Effect - Hearing your name is easy in a noisy place full of conversation, even if you weren't paying attention to the other conversations.
Other Attention Effects:
Divided Attention:

tring to focus on multiple things at the same time will reduce your ability to pay attention to them; especially true if the stimuli are from the same sense.

(it's easier to pay attention to a sight and a sound stimuli at the same time than it is to do so to two different sound stimuli)
Phenylthiocarbamide - genetic determination of tasting. dominant trait is to taste.
Detection vs. Discrimination

"there or not there?"


"same or different?"
* Theories of Colour perception, demo, then move on to states of consciousness; self study other stuff.... :(
A Couple Other Things:
Theories of colour vision
dichromatism (dichromatic colour blindness)

a form of color blindness in which the sufferer can perceive only two of the three primary colors and their variants.
Some neurons in your brain are for detecting lines, curves, and motion.

They are called "feature detectors" and they are very early in visual processing
The range of freuencies that humans can hear is generally stated at 20 Hz to 20,000 Hz.

Some animals will be able to hear in ranges outside of these (e.g. dogs can hear noises that are more high pitched than we can)
Weber's law - it is easier to notice a change if the stiumulus is less intense, and more difficult later.

can be expressed as:
In other words, if you have a very salty soup, you need to add a lot of salt to notice a difference,

but if you have a soup with almost no salt, you only need to add a little bit to notice a difference

This works for all senses, though the constant K will be different for each sense.
Sensory Thresholds:
(Smallest stimuli we can detect)
Error in Cram Kit:

pg. 23 - Q1 says the answer is Phi Phenomenon (pictures displayed quickly seem like motion, like movies)

but the actual answer is stroboscopic effect (like a strobe light, flashing lights make it seem less like motion and more like still frames.)

These two are kind of like opposites, so it's important to note the difference.

Bottom-Up Processing
Top-Down Processing
Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy, it deosn't mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.
Bottom-Up: Analysis that begins with the sensory receptors and works up to the brain's integration of sensory information.
Top-Down: information processing guided by higher-level mental processes, as when we construct perceptions that draw on experience and expectations
Selective Attention: focus of conscious awareness on a particular stimulus


Change Blindness
Absolute Threshold:
the minimum stimulation needed to detect a stimulus 50% of the time
Psychophysics: studies the physical energy we can detect and its effect on our psychological experience

Signal detection theory: predicts when we will detect weak signals

difference threshold: minimum difference a person can detect between any two stimuli half the time
What about subliminal priming? Does it work?
Sort of.
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