Sensation and Perception

I. Sensory ProcessesAll incoming messages must be interpreted

by the brainSensation is not just physical, it is also

psychologicalWe create meaning from what we know

Sensation – activation of our senses

Perception – process of understanding sensation

I. Sensory ProcessesWhat affects how we sense and perceive stimuli:

How long we are exposed (ex: socks)What we are focused on (voluntary v. involuntary cocktail-party

phenomenon)Sensation and perception happen through a

process called: TRANSCUDTION TRANSCUDTION:

signals transformed into neural impulses.sent to thalamus firstThalamus sends messages to correct part of the

brain

II. SensationVisionLight is reflected off objects and gathered by the

eyeWavelengths of light determine the hue we see

Longer wavelengths = infrared waves, microwaves, radio waves

Shorter wavelengths = ultraviolet waves, x-rays

II. SensationA. Structure of the eye

Cornea: clear covering of the eyeIris: colored, circular muscle – contracts/expands to

control lightPupil: opening in the eye (like shutter of a camera)Lens: part of the eye that focuses an object on the

back of the eye, focuses the light ***give me a finger***image is projected upside down

Retina: like a screen, contains neuron receptors for light

Optic Nerve (Blind spot): part of the retina where the optic nerve exits – no receptors for light (p. 4)

II. SensationReceptors in the Retina

Cones – first layer of cells, activated by light, colorRods – respond to black and white

More Rods than cones Peripheral **colored pencils**

Color VisionTrichromatic theory

Red, green, blueOpponent process theory

Red/green Yellow/blue Black/white Fatigue of sensors p. 100

Pic taken with colorized scanning electron micrograph (SEM)

cana

II. SensationColor defects, Color blindness

Red/green colorblindness most common (7-10% men)Color blind test

Feature detectorsWidth, depth, shape, curves, vertical lines,

motion, and many othersAfterimage – firing of cones not used after

viewing something in order to bring the visual system back in balance

II. SensationB. Hearing – auditory sense, uses sound waves

Sound waves created by vibrationsTransduction to neural messagesAmplitude – determines loudnessFrequency – determines pitch

Characteristics of SoundPitch – how high or low a sound isTimbre – complexity of sound (voices, instruments,

sirens)Intensity (decibels) – how loud more than 130 decibels = painful (p. 101)

II. SensationStructure of the Ear

Ear canal – auditory canal (external structure)Ear drum – skin stretched over entrance to ear, thin

membrane; vibrates to sound, connected to 3 bones Hammer Anvil Stirrup

Cochlea – snail shaped, fluidHair cells – receptor cells for hearing, when fluid

moves, hair cells move, tuned to different frequencies, lost with age

Auditory Nerve – sense message to brainDeafness – conduction v. nerve deafness

II. SensationC. Cutaneous Senses- touch

Cutaneous receptors respond to pressure, temp, pain

Receptors more sensitive in some parts of the body than others

All touch senses go to spinal cord Purpose of pain: defense mechanism Interpretation of pain: PLEASURE v. PAIN,

depending on intensity, environment, circumstance (psychological)

WHO????loves ice creamenjoys eating broccolihates spicy, hot, or strongly flavored foodshas a hard time deciding what to order at a

restaurantalways asks for sauces and dressings on the sidedives right into their food after being servedcarefully tastes each food on their plateadds a lot of saltHas ever been called a picky eater

Activity

Let’s answer the following:How did holding your nose and smelling mint

affect the flavor of the food sample?

What are some reasons why it would be important to distinguish different tastes?

Genes are only one factor that determine your food preferences. What else might affect food preferences?

II. SensationSmell (olfaction)

ChemicalsStrongly linked to memory (amygdala, emotion,

and hippocampus, memory area, in brain) Do not go to thalamus first, go directly to

emotion/memory area in brainMechanisms of smell

Cilia – tiny hairs receive odor molecules, send to olfactory bulbs

Olfactory bulbs - generate code that brain interprets

II. SensationPHEROMONESA study involving human subjects, conducted in Switzerland

by Claus Wedekind, consisted of 44 males and 49 females. The men were given t-shirts and instructed to wear the T-shirts to bed for two consecutive nights to ensure that the T-shirts were totally saturated with pheromones. They were also given scentless soap and other toiletries and told to use them exclusively. At the end of the experiment, the t-shirts were put into a box and rated, on the basis of smell, by women. A number of boxes were filled with clean t-shirts to act as a control.

The women were then given the boxes and asked to rate them according to their reaction to the different scents, that is whether they found them pleasant or unpleasant. The results found that the women preferred the scents of the T-shirts worn by men with a dissimilar MSC gene. Many of the women commented that the scents reminded them of boyfriends or husbands.

II. SensationTaste – chemical response

Tastebuds -Bumps on your tongue Signals go down into tongue and connect to brain Taste buds are all over tongue, insides of cheeks,

and roof of the mouth4 types of tastes

Sweet – vital for energy, desire for sweet is built in Salty – keeps body chemistry in balance Sour – food gone wild (bad…old) Bitter – detect poison

II. PerceptionThe difference between sensation and

perception =Sensation is like getting data from

environmentPerception is interpreting that date

II. Perception Top-down processing:

I _ope yo_ _ad a g_eat w__ken_.

use background knowledge to fill in the gaps

Schemas – mental representations of how we expect the world to be (from our experiences)

Perceptual Set – Predisposition to perceive something in a certain way.

EXAMPLE: Finding objects in clouds

II. PerceptionBottom-up processing

Aka feature analysisInstead of using our experience to perceive an

object – we use only the characteristics of the object to build a perceptoin

II. PerceptionA. Perceptual

Constancies – our ability to maintain a constant perception of an object despite changes in angle, lighting, etc…

a) Size - close=larger image on retina, far away = small image

II. PerceptionA. Constancies

a) Size – keep things the same sizeb) Color – knowing an object is the same color

regardless of environment (lighting) c) Brightness – keeps brightness of an object

constant d) Shape – objects viewed from different angles, but

we know shape remains constant (coffee mug)e) Space – ability to keep objects in the environment

steady a) Self-motionb) Object-motion

II. PerceptionB. Depth perception

a) Visual Cliff - experiment, proof of depth perception in early years

b) Binocular disparity – eyes see objects at different angles, when brought together, bring a sense of depth

a) With objects that are closer our eyes come together more, brain can sense muscle movement in eyes that bring them together, helps interpret that objects are closer

c) Visual Texture – depth perception based on how rough or smooth objects appear

II. PerceptionC. Perceptual Organization = Gestalt Rules

1. Gestalt Rules – helps give us the “big picture”Proximity -

Similarity -

Continuity -

Closure -

II. PerceptionIllusions

Muller-Lyer

Reversible figure -

Subliminal perception – stimulation presented below the level of consciousness

II. PerceptionPsychology in your life

Do you have ESP? – Ganzfeld procedure Telepathy –Reading someone’s mind Clairvoyance – seeing or knowing something

without being there, knowing when/what is happening at the moment something happens

Premonition or Precognition – Predicting the future Pscychokinesis – influence over/moment of an

object Sixth sense

Full mull mental hospitals

Most people think this is a trick, and that the shapes aren't actually the same in each image. Not so!

The illusion lies in the fact that the red and green triangles appear to be similar. They are not. The green one is 1 square taller than the red. To be similar, it would need to be 7·5 squares long - it's actually 8! This leads to a shallower gradient on its sloping side:

All of the lines are straight!

Lock your eyes on the black spot. Keep them there for 20-30 seconds. What do you notice?Due to the large expanse of white around the circles, once again our peripheral vision is interpolated by the brain. The black dot is rigidly defined, whereas everything else fades away to white. After a while, the brain forgets that a series of shaded circles exist, and fills in the information gaps with pure white.

In the same diagram on the right, it is impossible to achieve this, as no white surround is present. Also, the outside edge of the circle itself is now precisely defined by the edge with the

background.

How many horses do you see?

Concentrate on the center

Concentrate on the four vertical dots in the middle of the image below for 2 minutes.

Now, let your eyes slowly roll up a white wall into the ceiling. You'll see a circle of light. Keep staring at the circle...

What do you see?

http://www.ritsumei.ac.jp/~akitaoka/motion-e.htmlhttp://www.ritsumei.ac.jp/~akitaoka/index-e.htmlhttp://www.psy.ritsumei.ac.jp/~akitaoka/color2e.htmlhttp://www.ritsumei.ac.jp/~akitaoka/index-e.htmlhttp://www.ritsumei.ac.jp/~akitaoka/saishin-e.html http://images.google.com/imgres?imgurl=http://emergent.unpythonic.net/files/01131390746-two-optical-illusions/

anim.gif&imgrefurl=http://emergent.unpythonic.net/index.cgi/01131390746-two-optical-illusions&h=300&w=420&sz=5&hl=en&start=40&tbnid=0Z0QY9MlMp0jRM:&tbnh=89&tbnw=125&prev=/images%3Fq%3Doptical%2Billusion%26start%3D20%26ndsp%3D20%26svnum%3D10%26hl%3Den%26rls%3DGGLG,GGLG:2005-24,GGLG:en%26sa%3DN

http://www.foxnews.com/slideshow/scitech/2010/02/20/mind-bending-optical-illusions?slide=5

Works Citedhttp://www.pbs.org/wgbh/nova/teachers/

activities/0404_01_nsn.htmlhttp://www.macalester.edu/psychology/

whathap/ubnrp/smell/memhttp://www.perriconemd.com/category/dr.

+perricone/case+studies/pheromones.doory.hthttp://www.psychologie.tu-dresden.de/i1/kaw/

diverses%20Material/www.illusionworks.com/html/size_constancy.htmlml

psychology.about.com