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Chapter 5

Chapter 5 - Sensation, Perception, Attention

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University of Toronto St. George
Michael Inzlicht

Chapter 5 Sensation, Perception, and Attention How Do We Sense Our Worlds? Sensor y organs convert forms of physical energy into signals that the brain can understand Adaptive, provides information on threats and food varies between animals depending on their adaptive challenges Stimuli Must Be Coded to Be Understood by the Brain Sensory coding the way our sensory organs translate a stimulus physical properties into neural impulses E.g. a green stoplight will be coded by a particular pattern of neural responses in the retina, etc. Transduction receptors, specialized neurons in the sense organs, pass impulses to connecting neurons when they receive some kind of physical or chemical stimulation from the environment Connecting neurons transmit the information to the brain as neural impulses Most of this sensory information first goes to the thalamus, then to the cortex, where it is interpreted as sight, smell, sound, touch, or taste Two categories of sensory coding quantitative and qualitative Quantitative intensity, brightness, and loudness is often indexed by the neural firing frequency. Higher frequency means brighter or louder Qualitative colour, taste, smell different sensory receptors respond to different qualities of a stimulus. Simplest form would be to have a receptor type for every possible stimulus. Coarse coding in most sensory systems, sensory qualities are coded by only a few receptors, each of which responds to a broad range of stimuli, which are integrated to compute the final percept Psychophysics Relates Stimulus to Response Trying to understand the relationship between physical properties of the world and how we sense or perceive them www.notesolution.com Examines psychological experiences of physical stimuli How much physical energy is required for our sense organs to detect that energy, and how much change is required before we notice the change? Test limits of human sensory systems through careful study Sensory Thresholds o Absolute threshold the minimum intensity of stimulation that must occur before we can experience a sensation e.g. the faintest sound you can hear (defined as the stimulus intensity that is detected above chance) o Difference threshold the just noticeable difference between two stimuli; the minimum amount of change required for us to detect a difference. o Webers law The difference required increases as the stimulus becomes more intense. The size of a just noticeable difference is based on a relative proportion of difference rather than a fixed amount of difference. Signal-Detection Theory o Variable of human judgement means that the concept of an absolute threshold is flawed o Signal-detection theory detecting a stimulus requires making a judgement about its presence or absence, based on a subjective interpretation of ambiguous information. o Four outcomes of a test hit, miss, false alarm, correct rejection o Response bias participants tendency to report detecting the stimulus on ambiguous trials o Circumstances, beliefs and expectancies can also influence this soldier will err on the side of caution, so will doctor higher level processes influence how sensations are perceived. Sensory Adaptation o Sensory adaptation response to a stimulus changes over time. o Sensitivity to stimuli decreases. If a stimulus is presented continuously, the responses of the sensory systems that detect it tend to diminish over time. www.notesolution.com
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