Sensation and Perception

Sensation: your window to the world Perception: interpreting what comes

in your window.

Sensation• the passive process of bringing information

from the outside world to the body and the brain

• Process of sensing our environment through taste, sight sound, touch and smell

• Example:

Perception• the active process of

selecting, organizing, and interpreting the information brought to the brain by the senses

• Perception is the way we interpret sensations and therefore make sense of everything around us

• Example:

Bottoms-up Processing• AKA - Feature analysis• Begins with the sensory

receptors and works its way up to the brain

• Use the features of the object itself to process the information

• Examples:

Top Down Processing• Processing information from

the senses with higher level mental processes using our experiences and expectations

• Using your background knowledge to fill in the gaps

• Example:

Selective Attention• Ability to focus our conscious

awareness on a particular stimulus• Example:

Selective Attention

Cocktail-party phenomenon• The cocktail party effect

describes the ability to focus one's listening attention on a single talker among a mixture of conversations and background noises, ignoring other conversations.

• Form of selective attention.• Example:

Selective Inattention • Change Blindness/Inattentional Blindness -

Falling to notice changes in the environment• Example:

– Choice Blindness - failure to notice a switch in a choice that is made• Example:

– Change deafness – failure to notice a change in voices that are speaking• Example:

• Pop out – stimuli we don’t chose to attend to but they draw our eyes and demand our attention

• Example:

Psychometrics• Study of how

physical stimuli are translated into psychological experience.

• Psychologists use thresholds to measure these events

• Example:

Thresholds• Absolute threshold – minimum

stimulation needed to detect a stimulus of light, sound pressure, taste, or odor 50% of the time

• Examples:

Signal Detection Theory• Predicts how and when we

detect a signal amid background noise

• Assumes no absolute threshold

• Detection depends partly on a person’s experience, expectations , motivation and alertness… alertness…people respond differently to same stimuli

• Examples:

Subliminal Stimulation• Subliminal Stimulation –

below one’s absolute threshold for conscious awareness

• Example

• Priming – increased sensitivity to certain stimuli due to prior experience outside conscious awareness

• Example

Do Subliminal Messages work?

• Based on studies, some people do respond to stimuli below the absolute threshold, under some circumstances. – The problem is people

behave differently at different levels, so what could be subliminal (or below the threshold) for one person, may be supraliminal (above the threshold) for another person.

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Intensity of stimulus

Percentageof correctdetections

Subliminal stimuli

Backmasking- More Subliminal Messaging?

Listing to Songs in Reverse

• There are legends about hidden messages in songs - Led Zeppelin's Stairway to Heaven was one of the first songs to have supposed hidden, satanic messages.

– http://jeffmilner.com/backmasking.htm

• Why does this seem to work?

Difference ThresholdAKA • Just Noticeable Difference – the amount

a change needed in a stimulus (stronger or weaker) for us to recognize the change has occurred

• the greater the intensity (ex., weight) of a stimulus, the greater the change needed to produce a noticeable change.

• Example:

Weber’s Law• Related to JND• For people to really

perceive a difference, the stimuli must differ by a constant "proportion" not a constant "amount".

• Proportion varies depending on the stimulus

• Example:

Weber’s Law• JND = Constant (K) X Intensity– Pitch = .003 ( if someone sings a little off key,

we will be able to tell)– Loudness = .10– Saltiness = .20– Light = .08

• Example:

Sensory Adaptation• Diminished

sensitivity as a consequence of constant stimulation

• Example

Do you feel your underwear all day?