3
Date of Experiment: Date of Submission:
July 16 - 22, 2015 July 28, 2015
EXPERIMENT NO. 2:
Application of Weber's Law on Visual Perception
Abstract
The study aims to find out if the Weber's Law applies to the judgment of size. The experiment is done simply by using pencil, paper and ruler. The subject was asked to draw a line using a ruler with different size or length and must fill the paper with lines having 2, 4 and 6 inches. 10 lines must be present in each length and there will be a total of 30 lines in the paper. After completing the required number of lines, the subject should estimate the midpoint of the lines but they should cover the lines around it to avoid biases. The results support Weber's law on judgment size. 2 inch lines have lesser mean error than 6 inch line. 4 inch line has greater mean error than 2 inch line, Based on the results, the researcher concluded that there is a relationship between the Weber's law and visual perception of the subject.
Introduction
People tend to use visual perception in choosing what they want to see and what they don't want, it is a matter of perceiving stimulus in specific ways. There are a lot of related literatures suggests that perceptual set mostly affects the visual perception of a person. Perception then identified as a process of interpreting stimulus with other given sensual information. The subject experimented whether the length of line would justify the use of Weber's Law. This law states that the more intense the stimulus is when it comes to length or size, brightness and strength the hard it is to identify or to hit the target. Size is an important stimulus property and estimation of stimulus size constitutes a fundamental aspect of human cognitive functioning in daily life (Y.Pan, W. Zuo, and X.Yi, 2013). This also might be a reason why do we tend to have lesser mean error to the shortest line because we find the longest line to be difficult to identify the midpoint because of its length or size.
Methodology
Problem/Objective
To find out if the Weber's Law applies to judgment of size.
Materials
Paper with 2-, 4-, and 6-inches lines beginning at different starting positions from the edge. There should be 10 lines of each length, arranged in random such that the same length does not appear successively.
Design and Procedure
Each student id his or her own S. Use a sheet of paper to mask the lines so that only one line is seen at a time. S examines each line and marks lightly with a ballpen what appears to be the midpoint. When all 30 midpoints have been "subjectively" marked, measure each line with a ruler to the nearest 1/16 inch and mark the actual midpoint. Record the amount of error for each of the lines and direction (before the midpoint, a "minus" error; beyond the midpoint, a "plus" error).
Subjects
Participants in this experiment are third year psychology students from Department of Behavioral Sciences, University of the East-Manila.
Results
Table I
Amount and direction of error in judging the midpoint of lines
with varying length
TRIAL
2-Inch Line
4-Inch Line
6-Inch Line
1
0
0.6
0
2
- 0.06
0
- 0.13
3
0
- 0.13
-0.13
4
0
0
0
5
0
0
0
6
0
0
0
7
0
0
- 0.13
8
0
0
0
9
0
0
- 0.13
10
0
- 0.25
- 0.06
Mean 1
0.006
0.044
0.058
Mean 2
-0.0018
- 0.005
- 0.006
Discussion
There has been large number of researches found discussing the similar topic that the experimenter had. Most related literatures talk about how Weber's Law could be related or be supported by using different stimulus. This law usually applies first-order structures such as lengths, weight or pitch (Van Der Helm, P.A, 2010). There are different constancies considered in this experiment. One literature considered Elusive Parallel Law by Fechner, it states that when a perceived stimulus intensity is changed by something other than physical intensity such as adaptation, Webers's Law continues to hold. (Ross & Wade, 2010). Meaning, all just noticeable differences must be subjectively equal. If any stimulus property is changed, Weber's Law will still be considered depending on how it was intense or not. Another perspective of Weber's Law that has been considered is the idea of illusion for which it was said that the illusion effect vary from different response given (Anema, Wolswijk, Ruis & Dijkerman, 2008). The authors started an experiment which assessed on the effect of Weber's illusion in estimating the size of objects as their stimulus. By using grasping movements, they came to a result that a smaller object has significance in estimating the size then the subjects had a hard time estimating the large objects. Again, as Weber's Law supported, the more intense a stimulus in terms of size, length, brightness or color it harder it is to identify or hit the target. Another related literature (Van Der Helm, P.A, 2010) implies that symmetry can cause changes in visual perception in humans. The experimenter discussed whether symmetry with noise follows the Weber-Fechner Law. The experimenter gathered different stimulus that will be used in their experiment and they came up to an idea that in the cases of high levels symmetry, the amount of symmetry tends to be overestimated which they called symmetry effect then in low levels of symmetry, it tends to be underestimated which they called asymmetry effect (Van Der Helm, 2010). This idea is somehow related to Weber's Law in a ways that when the perception to the given stimulus changes, it will be hard to identify the just noticeable constant ratio.
Conclusion
The data gathered in the experiment justifies that the Weber's Law applies to judgement of size. Given the related literatures of different authors using different stimulus in the experiment, it is evidently shown that shorter line which is 2-inch has the least mistake in estimating the midpoint than the other lines which are 4-inch and 6-inch.
References
Van der Helm, P.A (2010) Weber-Fechner behavior in symmetry perception, attention, perception and Psychophysics, 72(7)
Ross, H.E & Wade, N.J (2010) Fechner's Elusive Parallel Law/Seeing and Perceiving 23 (2010)
Anema, H.A., Wolswijk, V.W., Ruis, C., & Dijkerman, H.C. (2008) Grasping Weber's illusion: The Effect of receptor density differences on grasping and matching, 25(7-8)
Pan, Y., Zuo, W., & Yi, X. (2013) The influence of visual short-term memory on Size Perception, 21(6)
Prepared By: Submitted to:
Viñas, Marian Roselle A. __________________________
Student Dr. Normaliza C. Ramirez, RP
Experimental PsychologyAPY 312-313 BS5BFirst Semester, SY 2015-2016
Experimental Psychology
APY 312-313 BS5B
First Semester, SY 2015-2016
