Introduction to: Sensation and

Perception

Advanced Placement PsychologyMrs. Kerri Hennen

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Sensation:The process by which our

sensory receptors and nervous system receive stimulus from the environment.

In other words: the process of bringing information from the outside world into the body and brain.

Perception:The process of organizing and

interpreting sensory information, enabling us to recognize meaningful objects and events.

Or, the active process of selecting, organizing, and interpreting information brought to the brain by the senses.

How do they work together?

Sensation occurs:– Sensory organs absorb energy from a

physical stimulus in the environment.– Sensory receptors convert this energy into

neural impulses and send them to the brain.

Perception follows:– The brain organizes the information and

translates it into something meaningful.

Bottom-Up vs. Top-Down Processing

Top-down processing:– Information processing that begins in

higher brain centers and proceeds to sensory receptors.

Bottom-up processing:– Information processing that begins at

the receptor level and continues to higher brain centers.

What if we could sense everything?

Life would hurt.

So we can only take in a window of what is out there.

This is the study of psychophysics:

relationship between physical stimuli and our psychological experiences to them.

Attention, not your attention. :)

Attention is:

the process in which consciousness is focused on particular stimuli.

There’s two types:

1. Selective Attention

2.Divided Attention

Selective AttentionThe focusing of conscious

awareness on a particular stimulus.

An example of selective attention is:

Cocktail Part Effect: ability to listen to one voice among many.

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Sensory Adaptation

A decline in receptor activity when stimuli are unchanging

Diminished sensitivity as a result of constant stimulation.

The concept of sensory adaptation applies to all of our senses.

Habituation

Decline in sensory sensitivity at the neural level due to repeated stimulation.

Different from sensory adaptation because

Simplest form of learning, and is the behavioral equivalent of an animal realizing that a stimulus is irrelevant.

Measuring this:

THRESHOLDS!

Absolute ThresholdThe point at which stimulation

is detected a 50% of the time.In other words, given a

particular stimulus, it’s the minimum stimulation needed for detection.

Difference Threshold:The minimum difference that a person can

detect between two stimuli 50% of the time.Also known as Just Noticeable Difference

(JND)

Can you tell the difference?

Weber’s Law:

The idea that, to perceive a difference between two stimuli, they must differ by a constant percentage; not a constant amount.

Signal Detection Theory:

Predicts how we detect a stimulus amid other stimuli.

Signal Detection Theory

Subliminal Stimulation:

Below one’s absolute threshold for conscious awareness.

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Does this work?

We do not perceive the world how it really is, but

as it is useful for us to perceive it.