Sensation and Perception
Sensation: your window to the world
Perception: interpreting what comes in your window.

Sensation
• Sensation the passive process of
• Process of sensing our environment through
• Example:

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

Bottoms-up Processing
• Bottoms-up Processing
(AKA - Feature analysis)
• Use the features of the object itself to process the information
• Examples:

Top Down Processing
• Top Down Processing -
Processing information from the senses
• Using your background knowledge to fill in the gaps
• Example :

Selective Attention
• Selective Attention –
• Example :

Selective Attention
Stoop Effect -

Cocktail-party phenomenon
• The cocktail party effect
• Form of selective attention .
• Example:

Selective Inattention
• Change Blindness/Inattentional Blindness -
Falling to notice changes
• Example:
– Choice Blindness - failure to notice
• Example:
– Change deafness – failure to
• 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
• Psychologists use thresholds to measure these events
• Example:

Thresholds
• Absolute threshold – minimum stimulation needed to
• Examples:

Signal Detection Theory
• Predicts
• Assumes no absolute threshold
• Detection depends partly on a person’s
• Examples:

Subliminal Stimulation
• Subliminal Stimulation – below one’s
• Example
• Priming – increased sensitivity to certain stimuli due to
• Example

Do Subliminal Messages work?
100
75
Percentage of correct
50 detections
25
0
Low
Subliminal stimuli
Absolute threshold
Medium
• 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.
Intensity of stimulus

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 Threshold
Difference Threshold –
• AKA Just Noticeable Difference
• the greater the intensity (ex., weight) of a stimulus, the greater the change needed to produce a noticeable change.
• Example:

Weber’s Law
• Webers Law (Related to
JND)
• stimuli must differ by a constant
• Proportion varies depending on the stimulus
• Example:

Weber’s Law
• JND = Constant (K) X Intensity
– Pitch = ( if someone sings a little off key, we will be able to tell)
– Loudness =
– Saltiness =
– Light =
• Example :

Sensory Adaptation
• Sensory Adaptation -
• Example:
Do you feel your underwear all day?