Sensation & Perception

(part 2) !

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Imperfect SensesHow are our senses imperfect?

!Limited Range:

Our senses pick up a limited range of signals (and their

range and sharpness is not as well developed as the senses are in some other species).

!Recall: the weakest amount of

a stimulus we can detect is called the absolute threshold.

There are 3 muscles in a human ear: humans can

hear 64-23,000 Hz. !

Dogs have 18 muscles in their ears: dogs can hear

higher pitched sounds and can detect a frequency range of 67-45,000 Hz.

Color-BlindnessThere are cones in the retina of the eye that respond to a specific range of light wavelengths. When some or all of a person’s cones do not function properly, he/she

is said to be color-blind or color-deficient. This is hereditary, and affects 7% of males and .4% of females.

Imperfect SensesHow are our senses imperfect?

!Context Clues:

Our brains use context to determine meaning. This

means that we compare what we see (or hear, smell, etc.)

to the surrounding environment and our past

experiences. !

How can this lead to misinterpretation?

!

!!!!

Our brains compare objects in the environment

to determine size.

Top-Down ProcessingTop-down processing suggests that we form our perceptions

starting with a larger object, concept, or idea before working our way toward more detailed information. In other words, top-down

processing happens when we work from the general to the specific.

Example: instead of processing each letter of a word, you read

the word as a whole. Your brain looks for familiar

patterns and uses context and prior knowledge to

understand overall meaning.

Top-Down ProcessingAoccdrnig 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.

If you can tell what these words are supposed to be, your brain is using top-down processing. It is focusing on the word as a whole

and the context of the sentence in order to understand meaning.

Bottom-Up Processing

Example: The first time you touched fire, the signal was sent from the environment to

your brain, and you pulled your hand away - this is bottom-up processing! (The next time you saw fire, you perceived it as hot before feeling the heat: this is top-down processing.

Bottom-up processing is the opposite: it suggests that we form our perceptions starting with individual details or components before working our way to an understanding of the whole. Bottom-up processing does not use context or prior knowledge to form

understanding, but it uses a direct stimulus: an individual image, smell, taste, or sound directly helps your brain create understanding.

Top-down & Bottom-UpImagine you are in your house at night in the dark.

When you hold out your hands in front of you to feel for furniture and walls, you are using bottom-up processing. You must use direct stimuli from the

environment to help form your understanding of the room in the dark.

When you try to remember what the room looks like during daytime, and use that prior knowledge to help you navigate the house in the dark, you are using top-

down processing. The concept you already have in your mind of the full house layout is helping form your

understanding of the room in the dark.

Pre-attentive ProcessThe unconscious accumulation and processing of

information from stimuli in the environment.

Attentive ProcessThe accumulation of information by actively and

consciously considering only one part of a stimulus at a time. Attentive thinking is slower, because the brain must consider one piece of information at a time…

Let’s try it out!

Say the colors: !

Green Red Orange Yellow Blue Green Purple Red Blue

Orange Yellow Green Red Blue Purple

the Stroop TaskPre-attentive!

the Stroop Task

Say the colors: !

Green Red Orange Yellow Blue Green Purple Red Blue

Orange Yellow Green Red Blue Purple

Attentive!

Gestalt LawsA series of principles that describe how we organize bits and

pieces on information into meaningful wholes.

Closure:We tend to ignore breaks in a figure, and instead focus on an

overall form.

1

Gestalt LawsA series of principles that describe how we organize bits and

pieces on information into meaningful wholes.

Proximity:We perceive elements that are

closer together as grouped together.

2

Gestalt LawsA series of principles that describe how we organize bits and

pieces on information into meaningful wholes.

Similarity:Elements that are similar in appearance we also see as

grouped together.

3

Gestalt LawsA series of principles that describe how we organize bits and

pieces on information into meaningful wholes.

Continuity:

Lines are seen as following the smoothest path.

4

Gestalt LawsA series of principles that describe how we organize bits and

pieces on information into meaningful wholes.

Simplicity:When we observe a pattern, we

perceive it in the most basic, straightforward way we can.

5 !!!!!!

You likely see a diamond shape with two lines on the sides before you see the letter W and letter M satcked on top of each

other.

MM

Gestalt LawsA series of principles that describe how we organize bits and

pieces on information into meaningful wholes.

Foreground/Background:We can identify a figure from the background. (This ability is

related to “simplicity”).

5b

Gestalt Laws

Gestalt memory device

Astronaut ManualRead assignment instructions on the Psych website.

Use Module 8 (page 89)

and Module 11 (page 116) to help you

complete this assignment.