Chapter 5 Notes .doc

Chapter 5 Sensation and PerceptionHow Do We Sense Our Worlds way we experience the world is divided into two sections sensation the organs responses to external stimuli and the transmission of these responses to the brain light air vibrations odoris an elementary experience such as colour or motion without the more complex perceptual experience of what is being seen or what is moving perception the processing organization and interpretation of sensory signals it results in an internal representation of stimulus often based on prior experiences which shape our expectations about new sensory experiences unlikely to see a blue applepshaped object as a real apple because you know apples are not blue our perception of the world does not work like a cameratape recorder what we sense is the result of brain processes that actively construct perceptual experiencesallow us to adopt to our environments detail Stimuli Must Be Coded to Be Understood by the Brain sensory coding our sensory organs translation of stimulis physical properties into neural impulses brain cannot process raw stimulimust be translated into chemical and electrical signals that the brain can interpret sensory coding begins with transduction a process by which sensory receptors produce neural impulses when they receive physical or chemical stimulation to function properly our brains need qualitative and quantitative information about stimuli qualitative knowing whether traffic light is green or yellow difference between salty and sweetquantitativecoded by the speed of a particular neurons firing a brighter light Psychphysics Related to Stimulus Response psychophysics examines our psychological experiences of physical stimulihow much change is required before we notice that change Sensory Thresholdsabsolute threshold the minimum intensity of stimulation that must occur before you experience a sensation the absolute threshold for hearing is the faintest sound a person can detect 50 of the time difference threshold the just noticeable difference between two stimulithe minimum amount of change required for a person to detect a difference the minimum change in volume required for you to detect a difference the difference threshold increases as stimulus becomes more intense Webers Law states that the just noticeable difference between 2 stimuli is based on a proportion of the original stimulus rather than on a fixed amount difference II11001you can detect a single candle when you have 10 candles Signal Detection Theory since people might convince themselves that a stimulus was presented due to questioning signal detection theory SDT a theory perception based on the idea that the detection of a faint stimulus requires a judgementis is not an allornothing process any trial in which participants judge whether an event occurs can have 1 of 4 outcomes hit if signal is presented and observer detects it miss if participant fails to detect a signal false alarm if participant detects a signal that was not presented correct rejection if signal is not presented and observer does not detect it response bias refers to a participants tendency to report detecting the signal in an ambiguous trial peoples expectations often influence the extent to which they are bias Sensory Adaptations sensory systems are tuned to detect environmental changes sensory adaptations a decrease in sensitivity to a constant level of stimulation researchers have noticed that if stimulation is presented continuously the responses of the sensory systems that detect it tend to diminish over time those who live near the airport become less aware of the airplane noises over time What Are the Basic Sensory Processes only the neurons in the sensory organs respond directly to events in the worldthe neurons in the brain do not respond to events in the world they only respond to input from other neurons In Taste Taste Buds Detect Chemicals gustation our sense of taste