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Chapter 5

chapter 5

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Steve Joordens

Chapter 5 SensationOur sensory nerves sense organs and our senses help us detect the world around us without these our brain would be useless We wouldnt be able to learnthink and have experiencesMilner and Goodale 1996 they used vision as an example as a control of distal sensory movement the animal makes that allows it to survive and reproduceSense systems rely on modality of the informationCharacteristics of the informationState of the brain at the time it receives itThe differences between the sources of information in the environment have different impacts on the way we sense and process the information For instance visual worldThe world as we see itis very rapid because our eyes have to adjust to light and see everything as we move our headsour body etc it is very rapid but yet we sense our vision to bestableauditory world This is different although the intensity of sound changes as we move closer or away from something there are less variables of sound and our perception is more gradual than vision Hence our ears have more time to process sound signals than our eyes to process vision signalsAs a result of this delay we can discriminate complex waveforms of the underlying soundsSenses all together contribute to the richness of our experiences Vision and Auditory capacity takes care of communication and seeinghearing things from a far while touch and smell have to do with things that are close by All this information helps us maintain our balance in our everyday livesSensory Processing Sensationthe detection of simple properties of stimuli such as brightnesscolor warmth and sweetness eg seeing the color red is a sensationPerception the detection of objects both animate and inanimatetheir locationstheir movements and their background eg seeing a red apple is a perceptionBack then psychologists used to believe that perception was based on learning but now they believe that experience has a lot to do with perception because they did not find clear boundaries between simple sensations and complex perceptionsWe know that they are 5 senses but in reality they are several of themTransductionDue to the fact that our brains are covered up and separate from the rest of our body it can only sense salt concentration in blood and temperature To perform useful actions we have to gather information from the external world this is done through the sense organs located away from the brainThese Sense organs transmit signals to the brain that coded to represent interactions with the environment transduction is the therefore the conversion of physical stimuli into changes in the activity of receptor cells of sensory organs Each organ receives a stimuli and transmits the energy gotten from the environment into neural firing which the brain responds toReceptor cellA neuron that directly responds to a physical stimulus such as light vibrationsor aromatic molecules In the sense specialized receptor cells release chemical transmitters that stimulate other neurons and alters their action potential and responds to the stimulus appropriately Some senses like body senses do not require specialized receptor cells however some of these neurons have specialized endings that enable to respond to particular kinds of sensory informationSensory CodingSensory information must accurately represent the environment However there are axons in the nerves that transmit action potentials which are limited in size and duration making it impossible to have different action potentials for different stimuli so the information the sense organs carry have to be coded so that we can sense different stimuli A codeis a system of symbols or signals representing information As long as we know the rules of the code we can convert a message from one medium to another They are 2 general forms of coding Anatomical Codingsensory organs send their information to the brain through different nerves and because the brain has no idea about physical energy on a given sensory organ it uses anatomical coding which isa means by which the nervous system represents informationdifferent features are coded by the activity of different neuronsTemporal Codingthis is the coding of information in terms of timeThe simplest form is rateThe faster or slower the rate of firing according to the stimulus tells the brain about quantitative information for instance a light touch means there is low rate of firingThe anatomical coding tells us about where the touch is while temporal coding tells us how intense the firing isPsychophysicsBirth in 19th century EuropeIt is study of the relation between thephysical characteristics of stimuli and the sensations they produceThere are 2 ways to examine and measure peoples sensations The Principle of the JustNoticeable difference jndErnst Weber17951878 he investigated the ability of humans to discriminate between various stimuli This is the smallest change in the magnitude of a stimulus that a person can detectHis experiment involved asking people if they could sense differences in the weight of two metals People reported that the weights were the same unless they differed by a factor of 1 in 40For instance the difference between 40 grams and 41 or 80 and 82
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