Module 17 Psychology
What is the function of sensory adaptation?
Sensory adaptation (our diminished sensitivity to constant or routine odors, sounds, and touches) focuses our attention on informative changes in our environment.
top-down processing
information processing guided by higher-level mental processes, as when we construct perceptions drawing on our experience and expectations
priming
the activation, often unconsciously, of certain associations, thus predisposing one's perception, memory, or response.
difference threshold
the minimum difference between two stimuli required for detection 50 percent of the time. We experience the difference threshold as a just noticeable difference (or jnd).
absolute threshold
the minimum stimulation needed to detect a particular stimulus 50 percent of the time.
Weber's law
the principle that, to be perceived as different, two stimuli must differ by a given percentage (rather than a given amount).
sensation
the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment.
perception
the process of organizing and interpreting sensory information, enabling us to recognize meaningful objects and events.
psychophysics
the study of relationships between the physical characteristics of stimuli, such as their intensity, and our psychological experience of them.
Using sound as your example, illustrate the distinctions among these concepts: absolute threshold, subliminal stimulation, and difference threshold.
Absolute threshold is the minimum stimulation needed to detect a particular sound (such as an approaching bike on the sidewalk behind us) 50 percent of the time. Subliminal stimulation happens when, without our awareness, our sensory system processes that sound (when it is below our absolute threshold). A difference threshold is the minimum difference for us to distinguish between two sounds.
Does perceptual set involve bottom-up or top-down processing? Why?
It involves top-down processing. Our perceptual set influences our interpretation of stimuli based on our experiences, assumptions, and expectations.
What are the absolute and difference thresholds, and do stimuli below the absolute threshold have any influence on us?
Our absolute threshold for any stimulus is the minimum stimulation necessary for us to be consciously aware of it 50 percent of the time. Signal detection theory predicts how and when we will detect a faint stimulus amid background noise. Individual absolute thresholds vary, depending on the strength of the signal and also on our experience, expectations, motivation, and alertness. Our difference threshold (also called just noticeable difference, or jnd) is the difference we can discern between two stimuli 50 percent of the time. Weber's law states that two stimuli must differ by a constant proportion (not a constant amount) to be perceived as different. Priming shows that we can process some information from stimuli below our absolute threshold for conscious awareness. But the effect is too fleeting to enable people to exploit us with subliminal messages.
What three steps are basic to all our sensory systems?
Our senses (1) receive sensory stimulation (often using specialized receptor cells); (2) transform that stimulation into neural impulses; and (3) deliver the neural information to the brain. Transduction is the process of converting one form of energy into another. Researchers in psychophysics study the relationships between stimuli's physical characteristics and our psychological experience of them.
How do our expectations, contexts, emotions, and motivation influence our perceptions?
Perceptual set is a mental predisposition that functions as a lens through which we perceive the world. Our learned concepts (schemas) prime us to organize and interpret ambiguous stimuli in certain ways. Our physical and emotional context, as well as our motivation, can create expectations and color our interpretation of events and behaviors.
What is the rough distinction between sensation and perception?
Sensation is the bottom-up process by which the physical sensory system receives and represents stimuli. Perception is the top-down mental process of organizing and interpreting sensory input.
What are sensation and perception? What do we mean by bottom-up processing and top-down processing?
Sensation is the process by which our sensory receptors and nervous system receive and represent stimulus energies from our environment. Perception is the process of organizing and interpreting this information, enabling recognition of meaningful events. Sensation and perception are actually parts of one continuous process. Bottom-up processing is sensory analysis that begins at the entry level, with information flowing from the sensory receptors to the brain. Top-down processing is information processing guided by high-level mental processes, as when we construct perceptions by filtering information through our experience and expectations.
Why is it that after wearing shoes for a while, you cease to notice them (until questions like this draw your attention back to them)?
The shoes provide constant stimulation. Sensory adaptation allows us to focus on changing stimuli.
perceptual set
a mental predisposition to perceive one thing and not another.
signal detection theory
a theory predicting how and when we detect the presence of a faint stimulus (signal) amid background stimulation (noise). Assumes there is no single absolute threshold and that detection depends partly on a person's experience, expectations, motivation, and alertness.
bottom-up processing
analysis that begins with the sensory receptors and works up to the brain's integration of sensory information.
subliminal
below one's absolute threshold for conscious awareness.
transduction
conversion of one form of energy into another. In sensation, the transforming of stimulus energies, such as sights, sounds, and smells, into neural impulses our brain can interpret.
sensory adaptation
diminished sensitivity as a consequence of constant stimulation.
