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Chapter 1

Chapter 1 Review: Percepetion

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Psychology 2115A/B
Christine Tsang

Chapter 1 Review What is Perception?  A conscious sensory experience  Whether or not that experience we perceive is conscious  Sensory experiences and how they result in our perception of the world and whether or not our perceptions can be altered separate from sensory experiences  Salvador Dali’s painting of old people/musicians – basic visual sensation in the lines of the drawing but there is also an effect of our perception of what we see within the picture  top-down/bottom-up effects  Bottom-up: data driven experience that we see and is processed by our brain  Top-down: the knowledge based system in which we are really looking for something in the picture that we know about already  We frame our sensory experiences in this way  We are always manipulating our senses to what our expectations are for our sensory experiences Why Study Perception?  Because you have to  Health and medical applications  Philosophical need to “know” enhanced awareness of ourselves  Figure 1 in text: cyclical process with no actual start or end o Our expectations and what the world is from a physical standpoint o The stimulus: all objects in the environment that are available to the observer o The electricity: the language of the brain – the brain only understands changes in voltages o Knowledge, experience/action: when we recognize something, we are categorizing the object – giving the stimulus meaning o Cyclical process that is continually changing and being modified as we are experiencing the stimulus itself  Figure 1.3 in text: transduction process o The creation of, or the change in, physical energy into electricity so that the brain can process the information o Turning the sensory stimulus into an electrical nerve impulse that will then we processes through the various circuitry of the brain o 4. Energy coming in and going through the dendrites o 5. Two neurons that are linked together – neurons activate one another in the chain o 6. Interactions across neurons – a single piece of transduced information is not passed from one neuron to another, but to hundreds How do you Measure Perception?  Qualitative Methods o Describing o Recognizing  Quantitative methods o Detecting o Perceiving magnitude o Searching Psychophysics: the measurement of perception o The relationship between the magnitude of a sensation and the magnitude of a stimulus that gave ride to that perceptual sensation o Understanding or measuring the relationship between the magnitude of a sensation and the magnitude of the stimulus that gives rise to the perceptual sensation o The measurement of how intense your perception of a particular stimulus is vs. how intense the actual physical stimulus is o E.g.: how much you have to turn a dimmer switch until you detect that the light is on Detection  How much stimulation is needed to know it is present? o Dimmer switch example – how much you have to twist the dimmer to know that there is a light in the room  Absolute Threshold: the minimum amount of stimulus energy that is present necessary for the observer to sense its presence  Psychometric function: the hypothetical relationship between the physical sensation/presence of the stimulus (e.g.: how bright the light actually is) and the psychological perception (e.g.: the light) o A function between two variables – the actual physical world and the psychological process that creates the perception of the physical stimulus in the world o Several ways of measuring psychometric function – 4 main methods to collect data to determine the psychometric function itself Method of Limits  A procedure to measure absolute threshold in which the experimenter presents stimuli in ascending order or descending order over various trials  Over these trials, the observer says whether they do or do not detect the stimulus  Various trials of the same stimulus and the same observer  Find the stimulus value where the observer last reports seeing the stimulus  Do an average of the yes/no point to determine the absolute threshold over various series of trials  Lots of psychological factors that contribute to our sensitivity of a particular stimulus – thresholds are not as definitive as is probably thought because of this Method of Adjustment  A procedure to measure absolute threshold in which the intensity is adjusted continuously until the observer can just barely detect the stimulus o Sort of similar to method of limits in the sense that we are increasing the stimulus energy until a person senses it or decreases it until they can no longer hear it o Combines the series into one instead of doing a series of the same tests  Staircase method: most often used method of adjustment o Pick a stimulus that is way above threshold and then decrease it step by step until the observer no longer detects it (make an error of judging whether the stimulus occurs or not) o When that error is made, the stimulus is increased until it is detected o Reversals  Go back and forth over and over again – each of these switches is called a reversal  Every time you're correct, the stimulus energy is lowered  If you are incorrect, the stimulus energy is raised o Should end up with something that looks like a staircase o End up with a narrow range of a series of trials where half of the time you are saying yes and the other half you are saying no  absolute threshold in this method o Creates a range where above it you always detect the stimulus and below it you never detect the stimulus o Trying to find the range where your guessing point is o Most studies look for 3-4 reversals  e.g. getting your eyes tested o Flaw: what if you never end up with any reversals or the reversals end up messed up? Never ending up with a reasonable mean o Also prone to bias – people who are very agreeable or very conservative – constantly saying yes/no Method of Constant Stimuli  A procedure to measur
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