Sensation & Perception
Sensation & Perception PSY 210
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This 3 page Class Notes was uploaded by Alvera Adams MD on Thursday October 29, 2015. The Class Notes belongs to PSY 210 at Wofford College taught by David Pittman in Fall. Since its upload, it has received 33 views. For similar materials see /class/230997/psy-210-wofford-college in Psychlogy at Wofford College.
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Date Created: 10/29/15
Thermal Thresholds Sensation amp Perception Detection differences based on somatosensory location Differences in psychophysical techniques Objectives 1 Determine the thermal threshold for the forehead the left palm and back of the right hand 2 Compare the processes of method of constant stimuli the method of adjustment and the method of limits as psychophysical tools to measure threshold 2 Locations Cognitive Testing RMSC 229D amp RMSC 229E Equipment Thermal delivery system consisting of a powerstat regulator 3 infrared heat lamps 250 watts and switches to control and deliver the stimuli Blindfold Procedure Save the individual data collection le from the course web site to the computer naming it as your own file You should open the data collection excel sheet You should enter and save the data for each subject in their own respective EXCEL sheets The subject should be blindfolded throughout the experiment You will use each psychophysical test to determine the threshold of all three locations forehead left palm back of right hand Adjust the lamps so that they are the correct distances from the hands and forehead 12 inches Both subjects should complete the method of adjustment rst After the rst subject has completed the method of adjustment the experimenter should switch places with the subject and the two students should repeat the experiment The students should do the same for the method of constant stimuli and the method of limits After both students have been tested using all three methods the data should be saved Take your individual THERMAL excel le with you and complete the data analysis After you have determined the threshold for all three methods you need to enter your thresholds into the Group data sheet found on the desktop of the NEURO4 computer Method of Adjustment The blindfolded subject has control of the powerstat and adjusts the thermal level to the minimal detectable stimulus for the forehead left palm and back of right hand Be careful in moving the powerstat so that the subject can control it The experimenter should manipulate the lamp selection and turn the stimulus button on and off at the subject s request Enter the Threshold data into the Data Collection Sheet in the thermalxls Excel workbook Method of Constant Stimuli In this experiment thermal stimulation is randomly delivered to the forehead left palm or back of the right hand A random order of stimuli has been created for you on the data sheet Set the thermal deliver system to the appropriate stimulus and hold the button down to deliver the stimulus The stimulus duration should be at least seconds to ensure that the subject receives the stimulus this is very important if the subject does not feel the stimulus the experiment will not work Approximately 1 second after depressing the button ask the subject for a response Saying the word stimulus is an appropriate prompt for a response of yes or no to indicate detection Be sure to enter data into Data Collection sheet Method of Limits Thermal stimulation is delivered in altering ascending and descending series You will deliver at least 2 ascending and descending series Use the following order FOREHEAD ascending descending ascending descending LEFT PALM ascending descending ascending descending BACK RIGHT HAND ascending J J39 J39 J J39 The 139 series should begin at 5 units on the powerstat and the descending series should begin at a level 15 units higher than the detected level of the previous ascending series Each stimulus trial should vary in multiples of 5 for example 5 10 15 etc and the stimulus duration should be at least sec as in the previous experiments The experimenter then increases ascending series or decreases descending series the intensity in multiples of 5 and the subject makes a detection judgment at each intensity until she or he responds yes that they did feel the stimulus in the case of an ascending series or no they no longer detect the stimulus in the case of a descending series Enter data into Data Collection Excel sheet The thermal level between the no to yes responses is the threshold and should be determined by the mean between for example 15 no and 20 yes would yield a threshold of 175 DATA ANALYSIS INSTRUCTIONS CONTINUED ON THE NEXTPAGE THERMAL LAB DATA ANALYSIS INSTRUCTIONS Open the data spreadsheet that you saved as your unique lename Click on the Data Collection Sheet and highlight columns A B amp C where you entered your data while conducting the lab and copy them Click on the Data Analysis sheet and paste the copied columns over columns A B amp C on this sheet Make sure that columns A B amp C are selected and choose the Data menu and the option Sort In the SORT dialog box make sure that the following options are chosen Sort by Stimulus Ascending My list has a header row Then click OK This should sort your data by body area stimulated and stimulus intensity low to high There are 4 trials for each stimulus intensity Calculate the percent of the trials in which you detected a stimulus and enter than percentage in the chart to the right of the columns FOREHEAD LEFT PALM RIGHT HAND Thermal Level Probabilit Probabilit Probabili 5 0 10 25 15 75 20 100 25 30 35 40 45 50 55 60 65 70 After you have entered in all of the probabilities then the Figure 1 should automatically be plotted and where each line crosses the 50 mark indicates the threshold of that body area as determined by the method of constant stimuli You will use Figure l in your report as an example of the method of constant stimuli Finally you should enter in the thresholds for each body area as determined by each psychophysical measurement in the Group data sheet on NEURO4
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