Lecture 4 notes - sensation and perception

Lecture 4 notes - sensation and perception - Lecture 4...

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Retina Lecture 4 Module 12 -17 12.1 Introduction to sensation and perception Perception: the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events. Interpretation of the sensory information Bottom-up processing: analysis that begins with the sensory receptors and works up to the brain‘s integration of sensory information Top-down processing: information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experiences and expectations. Sensation: Translation of physical energy from environment to neural signals. 12.2 Thresholds Psychophysics is the study of how this physical energy such as their intensity, relates to our psychological experience. Absolutes thresholds - the minimum stimulation needed to detect a particular stimulus 50% of the time. This 50/50 reconition of a particular stimulation signifies the Absolute threshold. Signal detection The ability to detect stimulus depends on the strength of the stimulus and also on our psychological state- our exp, expectation, motivation and alertness. Signal detection Theory: a theory predicting how and when we detect the presence of a faint stimulus in the middle of background stimulation. Assumes there is no single absolute threshold and that detection depends –partly on a person’s exp, expectation, motivation and alertness., -predicts when we will detect weak singles, measured as our ratio of “hits” and “False Alarms” and “miss” -signal detection can also have life-or-death consequences eg. War soldiers will fire at the slightest noise because of the immediate danger they are always in – however, when remove from the war soldiers do not respond as impulsively to such stimulus. Subliminal Stimulation: Subliminal: below one’s absolute threshold for conscious awareness Prime: the activation, often unconsciously, of certain associations, thus predisposing one’s perception, memory or response. While asked to express how one fells about a certain stimulus, a invisible image or word can briefly prime your answer to the question. Difference Thresholds (noticeable difference or jnd) The minimum difference between two stimuli required for detection 50% of the time. We experience the difference threshold as a just noticeable difference. Eg. 1 candle then 2 candle: the likelihood of noticing the difference is 100%
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eg. 15 candles then 15 candles: the likelihood of noticing the difference is drastically reduced Weber’s Law: the principle that, to be perceived as a difference, two stimuli must differ by a constant minimum percentage ( rather that a constant amount). *not the amount of stimulus that differs but the proportion. A constant proportion such as. .. Eg.
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Lecture 4 notes - sensation and perception - Lecture 4...

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