Marina Sangkavichai. Perceiving the World Sensory systems What are our senses? How do we make...

Marina Sangkavichai

Perceiving the WorldSensory systemsWhat are our senses?How do we make meaningful interpretations

from what our senses take in?

SensesSeeingSmellHearingTasteTouchWe have an amazing ability to distinguish

different sensations. For example, a touch sensation does not “feel” the same as a “hearing” sensation.

Sensation and PerceptionSensation: process that occurs when special

receptors in the sense organs are activated, allowing various forms of outside stimuli to become neural signals in the brain.

Perception: the method in which the sensations experienced at any given moment are interpreted and organized in some meaningful fashion.

Perception

Sensory CodingOur senses “boil down” floods of information

into a stream of useful data.After our senses analyze information, our

senses use sensory “coding.”Sensory coding: important features of the

world are converted into neural messages understood by the brain. Also known as “ transduction.”

Exercise: Put pressure on your eyes, hold for a few seconds. The pressure you put on your eyes is “encoded” into visual features…not pressure. This is because the retina encodes visual information.

SensesThe minimum stimulation necessary to

detect a particular stimulus ( light, sound, pressure, taste, odor ) is called its absolute threshold.

Example: we can feel a bee falling on our cheek, or smell a drop of perfume in a small apartment

How loud does someone have to call out your name before you can hear it.

Absolute Thresholds

Bacteria On Our Skin

Signal Detection TheoryThis refers to our attempt to focus on one particularstimulus and ignore the flood of information enteringour senses.

For example, focusing on a friends conversation at aparty while trying to ignore the surrounding noises.

Absolute ThresholdWhat is the dimmest light this lifeguard

could perceive in the darkness?

Absolute threshold measures have been established by sensory psychology.

Just as a threshold of a doorway is the dividing point between being outside or inside a room, the absolute threshold of a sense marks the difference between not being able to perceive a stimulus and being just barely able to perceive it.

Absolute ThresholdsAbsolute thresholds define the sensory

worlds of humans and animals.Humans can hear sounds down to 20Hertz ( vibrations ) per second and up to

20,000 hertz.This is a practical range because if your

ears could sense tones below 20 hertz, you would hear the movements of your muscles!

Absolute ThresholdsDogs, bats, and cats, and other animals can

hear sounds well above 20,000 hertz.Dog whistles ( 40,000 to 50,000) can be

heard by dogs but not by humans.For humans this sound is beyond our

awareness.

Absolute Thresholds The minimum amount of sensory stimulation that can be detected

50% of the time

Sensory AdaptationTendency of sensory receptor cells to become

less responsive to a stimulus that is unchanging.

Receptors are no longer sending signals to the brain

Clothes would drive us crazy, ticking of the clock, and odors from our home would not go away.

Perceptual ConstanciesThe perceived size of an object remains the same, even though the size of its image on the retina changes is called SIZE CONSTANCY. For example: hold your left hand up to your nose, and right hand at arms length. Has your right hand suddenly grown smaller? No

The Amazing EyeLight is one form of electromagnetic waves

which travel around us.The transparent covering on the front surface

of the eyeball that bends light rays inward toward the pupil is called the CORNEA.

The EYEThe cornea bends light inward and usher

it into the pupil which is the small dark opening in the color of the iris. ( the pupil is a hole in your eye ). The iris controls the contraction of this pupil. It is an involuntary reflex.

In very bright light, it can contract to the size of a head pin.

In dim light, ( dark) it dilates ( that is WIDENS) to the size of a pencil eraser. Why do you think this is so?

The EYEYour pupil responds to emotions as well as

light!When a person looks at someone or

something highly desirable, the pupils dilate ( widen ) as if to take in more of the pleasing view!

It also dilates ( widens ) when a person is frightened, telling a lie, or sexually aroused.

Pupil size is also related to mental effort, the more intense the mental activitiy, the larger the pupil becomes.

Wide Pupils More Attractive

Hess Studies In one of the studies they

conducted, they showed men two sets of photographs of women. In one set, the pupils of each woman had been enlarged. In the other set of photos, the pupils of each woman had been reduced. Results showed that the men preferred the photos of the women with the enlarged pupil, even though the men could not explain why those were their favorites. When the test was performed on a group of women, the results were the same.

The EYEThe lens is just behind the iris and the pupil.

This changes shape as it focuses on the retina.

The retina is at the back of the eye. Images are projected from the lens.

Depth Perception Depth Perception: is the ability to see three

dimensional space and to accurately judge distances. You wouldn’t be able to drive a car or ride a bicycle, play catch, etc.

The world would look like a flat surface!Images cast on the retina do not contain

depth. They are flat, just like a photograph. So how do we perceive depth????

Binocular Depth CuesBinocular depth cues are depth cues that

depend on two eyes working together.Close one eye and see how your visual world

changes!

Binocular Depth CuesEach eye is about 2 ½ inches apart, just

enough to give each eye a slightly different view of the objects focused on, and consequently a slightly different retinal image.

These slightly different views are called binocular disparity.

Class ExerciseHold a pencil/pen at arms length straight in

front of you. Then close your right eye and focus on the pencil, then left, than right.

The pencil will appear to be moving side by side. This is BINOCULAR DISPARITY.

Two different images on the retina which allow you to perceive depth. Helps us see things in 3D. Each eye gets a different view of the world, this provides you with depth perception.

A Hole In Your HandInstructions: Roll a piece of paper into a tube.

Close your left eye. Hold tube to your right eye like a telescope. Place left hand halfway down tube. Now open left eye.

You will see a “hole” in your hand. Your brain blends these two images automatically.

The Visual Cliff ExperimentResearchers Eleanor Gibson and Richard Walk

wanted to test depth perception in childrenBuilt a special table that had a big drop on one

side. They called it the “visual cliff.”Different size of the pattern was a clue for

depth. Whole table was then covered by a clear glass

top, so that a baby could safely be placed on or crawl across the “deep” side. ( video )

Youtube.com Visual Cliff ( 1950s) Joseph Campos-Visual Cliff

Visual Cliff ResultsInfants tested in this study ranged from 6

months to 14 months old.81 percent refused to crawl over the deep

side.They interpreted this as a very early sign of

depth perception.

Gestalt Theories of PerceptionGestalt A German word that refers to the whole form, pattern, or

configuration a person perceives

Figure-ground When viewing the world, some object (the figure)

often seems to stand out from the background (the ground)

Figure-Ground Images

Figure Ground Images

Gestalt Principles of Grouping

Perceptual ConstanciesAllows perceived objects to maintain stable properties

(size, shape, brightness) despite differences in distance, viewing angle, and lighting:

Size constancy – as objects move away they seem to maintain same size

Brightness constancy – objects seem to maintain a constant level of brightness regardless of differences in lighting conditions

Shape constancy – objects are perceived as having an unchanging shape regardless of viewing angle changes that alter the retinal image

Perception of Images

Perception Exercise

Cultural Influence on Emotional Perceptions

Two studies tested the hypothesis that in judging people’s emotions from their facial expressions, Japanese, more than Westerners, incorporate information from the social context. In Study 1, participants  viewed cartoons depicting a happy, sad, angry, or neutral person surrounded by other people expressing the same emotion as the central person or a different one. The surrounding people’s emotions influenced Japanese but not Westerners’ perceptions of the central person. These differences reflect differences in attention, as indicated by eye-tracking data (Study 2): Japanese looked at the surrounding people more than did Westerners. Previous findings on East–West differences in contextual sensitivity generalize to social contexts, suggesting that Westerners see emotions as individual feelings, whereas Japanese see them as inseparable from the feelings of the group. (…)

Influences on PerceptionAttention

Process of sorting through sensations and selecting some for further processing Some sensations are automatic requiring minimal mental effort

Inattentional blindness Changes in objects not receiving direct attention are not noticed

Cocktail party phenomenon When you hear your name, focus follows due to assumption that

other meaningful information will follow Focus

Information that receives focus is remembered while other stimulation received at same time is lost Hearing words spoken into both ears at same time; only words

that receive focus of attention are recalled (Invisible video)

Piano Stairs in Sweden A Volkswagen initiative called The

Fun Theory is setting out to prove that people’s behavior can be changed for the better by making mundane activities fun. In a recent experiment, they set up musical piano steps on the staircase of a Stockholm, Sweden subway station to see if more people would be more willing to choose the healthier option and take the stairs instead of the escalator. That day, 66 percent more people took the stairs than usual, proving that fun is the best way to get people to change their ways.

© E.R. Degginger/Animals Animals

What do you see?

Can you find the human face here?

Optical Illusion

Curved lines or straight lines

Which one of the surrounded circles is bigger?

What do you see?

How many prongs are there?

There’s a baby in this picture

Animals on hands!

Guido Danieli Animal on Hands

Impossible Scenes

Psychology QuestionPlease define the terms sensation and

perception.

If a tree makes a sound in the forest, does it still make a sound? What are your thoughts?

Supermarket PsychologyConsumers buying more than what they needSlow musicRed and yellow are NOTICEABLEGreen evokes feelings of healthBlue means reliable and trustingVisual merchandising is keyFresh flowers in the front to appeal to your

sense of smell! Oh, earthly joy!Cereal and coffee usually in the middle aisles!

HearingHow do humans hear?By picking up sound waves in the air.Sound waves are invisible ripples of high and

low air pressure created by objects that vibrate or shake rapidly to and fro.

You can “feel” sound waves if you’ve ever put your hand on a loud, booming speaker.

Sounds WavesA little science!Sound waves have amplitude ( which is the

height of each wave and frequency which is the number of waves per second).

Low pitch sounds have low frequency, and low amplitude

High pitch sounds high amplitude and high frequency. Illustration.

How we hear!The ear converts this type of energy-in

this case the energy of sound waves, into tiny electrical nerve signals.

Sound waves are transmitted into the cochlea, a snail shaped tube in the ear. There are tiny hairs in this cochlea that are stimulated. These vibrations are then transmitted to the brain as sound.

Exposure to loud noises can damage the ear so be careful….jack hammers, airports, etc.

SmellAirborne molecules must reach receptors in

the back of the nose in order to smell.Sniffing swirls the air up into these receptors. Messages from these receptors are sent to

the brain temporal lobe and to parts of the limbic system.

That’s why certain smells conjure up memories!

Smell is important because it signals us to dangers in our environment such as smelling something burning, poisonous gases, etc.

TasteYour tongue is covered with small bumps called

the papillae. Each papillae has 100-200 taste buds ( sensory receptors of taste!)

Basic taste sensations are sweet, salt, sour, bitter,

Smell and taste work together ( colds don’t help!)

Taste adds to our enjoyment of food.Taste signals travel slowly to the brain ( it may

take a few seconds to realize what the taste is ).End of lecture