How reliable is our perception?

How reliable is our perception?

We use our senses to acquire information that we use to produce knowledge.

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Our ability to see, hear, feel, taste, and smell are fundamental to

our memory, thinking, and behavior.

But do our senses give us an accurate picture of our environment?

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Can we trust our senses?

Important to understand:

SENSING vs. PERCEIVING

• Sensation = a PASSIVE process in which sensory organs receive info from the external world

• Perception = an ACTIVE process of the mind that makes meaning out of sensory info

Under normal circumstances,

sensation & perception blend

into one continuous process.

An example of sensation WITHOUT perception:

• Prosopagnosia (Face Blindness)

• A neurocognitive disorder involving the inability to recognize faces

• Condition may be inherited OR acquired (stroke or brain injury)

• Affected brain region is the fusiform gyrus (temporal lobe)

Bottom-up processing

• starts at your sensory receptors and works up to brain's integration of sensory information

• e.g. taste buds --> flavor identification

Top-down processing

• perception guided by higher-level mental processes

• draws on our experiences and expectations

What factors affect our perception?

Selective Attention

• focusing of conscious attention on a particular stimulus

• cocktail party effect (ability to pay attention to just one voice among many)

• inattentional blindness (failing to see visible objects when our attention elsewhere)

Sensory Adaptation

diminished sensitivity because of constant stimulation

Signal Detection

idea that detection of stimuli depends partly on a person's experiences, expectations, motivation, and alertness

(This predicts how/when we will detect the presence of a faint stimulus.)

Sensory Interaction

• one sense may influence another

• e.g. the smell of food influences taste

Gestalt principles, depth perception cues & perceptual constancies

Sensitivity of receptors

absolute threshold = the minimum amount of stimulation required to produce a sensation; the lowest or weakest level of stimulation (e.g., the slightest, most indistinct sound) that can be detected on 50% of trials

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difference threshold = the smallest difference (AKA "just noticeable difference") between two stimuli that can be consistently and accurately detected on 50% of trials

Weber's Law (of Difference Threshold)

• The ratio of initial stimulus magnitude to background is constant

• So... when you're in a noisy environment, you must shout to be heard while a whisper works in a quiet room

   

Perceptual Set

a temporary readiness to perceive certain objects or events rather than others

Schemas

• concept or framework that organizes and interprets information

• developed through experience

• These determine our perceptual set

Context

• "eel is on the wagon" vs. "eel is on the orange"

• culture

• emotion

Context Example

What emotion is this?

SEE UPPER LEFT

Cultural Context

What is above the head of the woman in the green shirt?