PSY 101 Lecture Notes - Lecture 6: David H. Hubel, Torsten Wiesel, Absolute Threshold
Chapter 6- Sensation and Perception
ā¢ The studī of hoī the īoīld out theīe gets iī
¶ā¦hoī īe īoī
¶stīuīt iī
¶teīī
¶al īepīeseī
¶tatioī
¶s of the
external world.
o Sensation refers to the stimulation of the sensory organs by physical energy from the
external world, and the conversion of this energy into neural signals.(eyes by light waves
and ears by sound waves)(transduction is the conversion of energy into neural signals)
o Perception refers to our interpretation of what we sense based on experience,
expectations, and surroundings.
o Sensation and perception are not the same thing. For example, people who suffer from
prosopagnosia cannot perceive human faces, but they can perceive objects.(in
attentional blindness)
o Sensing the World: Basic Principles
o Thresholds
o Absolute threshold-the minimum stimulation necessary to detect physical stimulation
half the time; that is, a particular light, sound, pressure, taste, or odor.
o The absolute threshold for human vision is equivalent to the amount of energy emitted
by a single candle on a completely dark night from 30 miles away, while that for hearing
is equivalent to the amount of energy emitted by the tick of a watch at 20 feet.
o Signal Detection
o Psychophysics is the study of the relationship between physical characteristics of
physical stimuli and our perceptual experiences of them, and makes use of signal
detection to measure absolute thresholds and other properties of sensation and
perception.(physical world, psychological world: light, brightness/sound,
volume/pressure, weight/sugar, sweet)
o In a signal detection task, across a number of trials, stimuli of different intensities are
presented. The test-takeīās task is to iī
¶diīate īheī
¶ he or she perceives the stimulus,
and absolute threshold is the intensity at which he or she is correct 50% of the time. The
above graph shows that the absolute threshold for vision is about 12 lumens (measures
of the intensity of light).
o Stimuli below the absolute thīeshold aīe suīliī
µiī
¶al ī¾liteīallī īīeloī thīesholdīīæ, aī
¶d īe
are influenced by subliminal stimulation.
o For example, subjects rated people in photos as more attractive if they were followed
by subliminal presentation of a positive image instead of a negative image.
o Hoīeīeī, effeīts of suīliī
µiī
¶al stiī
µulatioī
¶ aīe fleetiī
¶g, aī
¶d theīeās ī
¶o eīideī
¶īe foī
powerful, enduring effects on behavior- such as those that would have to occur to make
soī
µeoī
¶e get out of theiī seat aī
¶d īuī popīoīī
¶ā¦ oī īhaī
¶ge hoī theī īote
o Vision
o The Stimulus Input: Light Energy
o Wavelength refers to the distance between one wave peak and the next, and
determines hue (color). (Short wavelength = high frequency (bluish colors, high-pitched
sounds), long wavelength = low frequency (reddish colors, low-pitched sounds))(short
wavelength-long wavelength = rainbow colors from purple to red)
o Intensity refers to the amplitude of the light wave (its height), and determines
brightness.
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