Lab 3 – Worksheet.pdf - Lab 3 – Worksheet Today we are...

Lab 3 – Worksheet
Today we are going to measure the size of your illusion using the method of constant
stimuli. In this method, we are going to keep the length of the reference line constant (i.e.,
the line on the left will always be 160 pixels). On each trial you will see different lengths of
the line on the right, and you need to decide whether the line on the right appears longer or
shorter than the reference line.
1) In the online experiment you viewed 13 different line lengths. Each line length was
viewed 4 times. At the end of the experiment, the computer displayed the mean % of
the time you said “longer” for each of the lin e length. Copy those means into the
chart below.
Line
Length
(dpi)
Mean % of the
time you said
Longer
150 0
155 0
160 0
165 0
170 0
175 25
180 25
185 75
190 75
195 75
200 100
205 100
210 100

2) Create a graph to calculate the size of your illusion (you can do this by hand or by
using the excel/google spreadsheets template). Please paste your graph below.
3) Provide a definition of the Point of Subjective Equality (PSE) and the Point of
Objective Equality (POE).