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Chapter 5

Psychology 1000 Ch.5 Notes: Very Comprehensive and Organized

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Western University
Psychology 1000

Chapter 5 NotesSensation and PerceptionSynaesthesia mixing of the senses Experiencing sound as colours or tastes 1 in 150 women have it 1 in 7150 men have itThese people provide glimpses into different aspects of how we sense and understand our worldSpecific types of stimuli activate specialized sensory receptors Stimulus can be light sound waveschemical molecule whatever These are translated into nerve impulses the only language the nervous system understands Stimulus is matched within an internal storehouse of knowledge which allows us to recognize the stimulus and give it meaning Then we consciously experience a perceptionSensation Stimulus detection process where our sense organs respond to and translate environmental stimuli into nerve impulses that are sent to the brain Perception Making sense of what our senses tell us The active process of organizing this stimulus input and giving it meaningThe same sensory input may be perceived in different ways at different times because perception is active and a creative procesessFor example ABC We perceive the middle symbol as B12 13 14 We perceive the middle symbol as 13Sensory ProcessesSenses vision audition touch gustation olfaction But there are more Senses that provide info about balance and body position touch can be subdivided into pressure pain temperature etc Human Sensory systems are designed to extract from the environment the info we need to function and survive We have specialized sensors that can detect different kinds of stimuli with considerable sensitivityPsychophysics Relations between physical characteristics of stimuli and sensory capabilities and is concerned with 2 kinds of sensitivityThe first concerns absolute limits of sensitivityThe second concerns with the difference between stimuliStimulus Detection The Absolute ThresholdOften unsure of whether weve actually sensed very faint stimuli researchers designate the Absolute Threshold the lowest intensity at which a stimulus can be detected correctly 50 of the time The lower the threshold the greater the sensitivity Our senses are very sensitive imagine thatAbsolute Threshold for smell One Drop of Perfume in a large apartment We can pick up on thatSignal Detection TheoryFound that peoples sensitivity can fluctuateThe concept of an absolute fixed threshold is inaccurate because theres no single point on a detection scale that separates nondetection from detection There is a range of uncertainty people set their ownDecision Criterion Standard of how certain they must be to determine a stimulus is present before theyll say they detect itCan change based on fatigue expectation or significance of stimulusSignal Detection Theory is concerned with the factors that influence sensory judgement Perception is in part a decisionFocus on Neuroscience The Neurosciences of Subliminal Perception in PropagandaSubliminal Stimulus received by the senses but not noticed by youThese stimuli can however affect behaviour and attitudes without us knowing Persuasive stimuli above the absolute threshold are far more influential than subliminal attempts to sneak into our subconscious mind maybe because were more likely to get the messageProsopagnosia Inability to recognize familiar facesVisual Agnosia is specific for facesHigher order facial recognition involves LOA FFA Brain regions But you can give certain info about visual stimuli faces even if one of these areas are damagedSubliminal cues can bias what we perceive at a conscious level and may alter our conscious experience of those stimuli study showed that subliminal presentations of aggressively tones words caused people to judge the ambiguous behaviours of others as more aggressive and to increase their own tendency to behave aggressivelyWe may not be consciously aware of the stimuli but aspects of the stimuli are processed at a different level and available for us to use in subsequent decisionsThe Difference ThresholdSmallest Difference between two stimuli that people can perceive 50 of the timeSometimes called the just noticeable difference or jndWebers Law States that the difference threshold is directly proportional to the magnitude of the stimulus with which the comparison is being madeexpressed as a Weber FractionJND value for weight150If you lift a weight of 50 grams another weight must weigh 51 grams for you to tell the difference500 grams other weight has to weigh 510 gramsWeber Fractions show that humans are very sensitive to audition tonal pitch and vision But least sensitive to taste and smell
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