Chapter 5: Sensation and Perception
What we see, hear, taste, smell or feel from touch results from brain processes that actively
construct perceptual experiences from sensory information. This constant conversion of
sensation to perception allows us to adapt to the details of our physical environments.
5.1
Sensation = the detection of physical stimuli and the transmission of this information to the
brain. (light, soundwaves, molecules of food, temperature, pressure changes)
→ involves no interpretation of what we are experiencing
Perception = the processing, organization and interpretation of sensory signals in the brain.
Bottom-up processing = Perception based on the physical features of the stimulus
Top-down processing = The interpretation of sensory information
based on knowledge, expectations and past experiences.
→ through top-down processing we are able to make sense of
“incorrect” stimuli
(e.g. Y0U C4N R3Ad TH15)
Context affects perception: What we expect to see (higher level)
influences what we perceive (lower level).
Transduction = the process by which sensory stimuli are
converted to neural signals the brain can interpret.
→ sensory receptors receive stimulation (physical stimulation in
the case of vision, hearing and touch & chemical stimulation in the
case of taste and smell) and pass the resulting impulses to the
brain in the form of neural impulses.
Qualitative information → consists of the most basic qualities of a
stimulus. (e.g. difference between red or green traffic light)
Quantitative information → consists of the degree or magnitude
of those qualities (e.g. how bright the light is)
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, 5.2
Psychophysics → examines our
psychological experiences of
physical stimuli.
Absolute threshold = The
minimum intensity of stimulation
necessary to detect a sensation half
the time. (the intensity of stimulation that must occur before you experience a sensation)
Difference threshold (just noticeable difference) = the minimum amount of change
required to detect a difference between two stimuli.
Weber’s law → the just noticeable difference between two stimuli is based on a proportion of
the original stimulus rather than on a fixed amount of difference.
signal detection theory (SDT) = a theory of perception based on the idea that the detection
of a stimulus requires a judgment; it’s not an all-or-nothing process.
response bias = a participant’s tendency to report or not report detecting the signal in an
ambiguous trial
Sensory adaptation = a decrease in sensitivity to a constant level of stimulation
5.3
synesthesia = when a visual image has a taste
5.4
Light first passes through the cornea (thick, transparent outer layer of the eye) where the
light is bent further inward and focused to form an image on the retina.
Retina = The thin inner surface of the back of the eyeball, which contains the sensory
receptors that transduce light into neural signals.
The cornea is not adjustable, but the lens is.
Pupil = dark circle at the center of the eye; a small opening in front of the lens
→ by contracting (closing) or dilating (opening), the pupil determines how much light enters
the eye.
Iris = a circular muscle
→ determines the eye’s color and controls the pupil’s size.
Accommodation = muscles change the shape of the lens; flatten it to focus on distant
objects and thicken it to focus on closer objects
presbyopia = the lens hardens as people get older and it becomes more difficult to focus on
close images.
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