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Sensation and Perception. Part 1: Psychophysics AP Psychology Zahuta. Sensation and Perception. Sensation – the stimulation of sense organs - absorption of energy (light/sound waves) by sensory organs (eyes/ears)
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Sensation and Perception Part 1: Psychophysics AP Psychology Zahuta
Sensation and Perception • Sensation – the stimulation of sense organs - absorption of energy (light/sound waves) by sensory organs (eyes/ears) Perception – the selection, organization, and interpretation of sensory output -translating sensory input into something meaningful.
Example Sensation = hearing the voice Perception = recognizing/associating it as your friend.
Psychophysics Study of how physical stimuli are translated into the psychological experience. How do we process/ understand the things we see and hear around us? Gustav Fechner 1860 University of Leipzig
The Threshold • Fechner – “For any given sense, what is the weakest detectable stimulus?” • Ex. What is the minimum amount of light for someone to recognize they see light? • Absolute Threshold= Minimum amount to be detectable Gradual response as stimuli increases Nothing absolute about it The Threshold *dividing point between energy levels that do or do not have a detectable effect
JND (Just Noticeable Difference) The just noticeable difference in stimulus intensity that a specific sense can detect. very similar to absolute threshold Easiest example is weight. JND=greater for heavy objects than for light ones. vs. Proportional to the original objects weight
Weber’s Law Fechner’s bro-in-law Weber’s law- the size of the JND is a constant proportion of the size of the initial stimulus - Applies to all senses *matches Fechner’s idea of threshold to the concept of detectability and probability.
Signal Detection Theory (SDT) -How stimulus are detected- Needs a decision process AND a sensory process –susceptible to influence from a variety of factors besides stimulus intensity. Ex. Trying to detect a knock at the door in the middle of a huge party
4 possible outcomes in SDT • Hit- Detecting signals that are present • Miss- failing to detect signals when they are present • False Alarm – detecting signals when they are not present • Correct Rejections – not detecting signals that are absent
How does decision making affect stimulus detection? • Must decide if stimulus is present • Criterion – expectations and consequences • Awareness of outside “noise” that can make detection more difficult.
Perception without Awareness • Subliminal Perception below the threshold sensory input without conscious awareness James Vicary (1957) Subliminal messages throughout Movie “Eat popcorn!” Sales by 58%!?
Subliminal Advertising KFC Coca-Cola
Subliminal Messages in Music The Beatles Led Zeppelin Britney Spears?!
Subliminal Messages in Disney Movies?! Are people defenseless against subliminal messages?? Operating below threshold awareness
Perception without Awareness • CAN TAKE PLACE?? • Jon Krosnick (1992) Sensory Adaptation gradual decline of sensitivity to prolonged stimulation ex. Jumping into a cold pool “come on in, the water’s fine!” - Automatic/built-in process - Focus on Changes instead of Constants - Evolutionary Psych
In Conclusion Important to Remember- There is no one-to-one correspondence between sensory input and sensory experience. Next we will look at the Visual System…How do we draw in visual sensations?