The Ponzo Execlusion: A Geometrical Analytical Illusion

The Ponzo Illusion is a geometrical optical illusion which suggests that the human mind judges an object's size based on its background. This illusion takes place when two lines that are equal in size are placed between converging lines and seen as being different lengths. A visual example of a Ponzo Illusion would be a railroad track with a sunset as the background. The perpendicular lines that run vertical outside of the horizontal ones give the illusion that the tracks may actually be going off into the sunset. The participant’s perception of the lines between the other objects is what creates the illusion. Various studies have found a possible correlation between this illusion and other factors. The factor we will be exploring is
age.
Studies conducted by Leibowitz and Heisel found a connection between the age of the participant and the perception of the lines (Hanley and Zerbolio, 1965).
Another factor that relates to age would be the constancy scale. A constancy scale is said to stimulate the illusion that one line is further than the other because it is being overestimated. This is correlated with age in the fact that those that have experienced more linear cues will recognize the similarities in the lines (Wagner, 1977). Another study found that children ages 5 to 6 underestimated the size of the lines while those 7 to 10 years old and older adults guessed the size of the lines with more accuracy. On the other hand, young adults tended to overestimate the line size significantly (Kavsek and Granrud, 2012). While these studies focused on the age of the participants other studies found that other factors played a role in the effects of the Ponzo
Illusion.
A study by Daniel Wagner takes into account age along with schooling and environment as factors of the Ponzo Illusion (1977). Wagner references Piaget and his studies about Type I and Type II illusions. Ponzo Illusion, according to Piaget, would fall under Type II as an illusion that increases with age. In Wagner’s study he details how the lack of an environment containing various linear images can affect how one sees a Ponzo Illusion. This illusion susceptibility could be caused by systematic variations rather than solely on the age of the participant.
Researchers Hanley and Zerbolio found another explanation in the variation between the different ages (1965). Both conducted an experiment using an up-down method with participants ranging from nursery school to college students. They offered each group only one chance for each trial which eliminated a starting position effect and error. With the nursery school children the researchers found an excessive amount of variability but for college students the variations were far less. The main discrepancy with the ages and perception was with the nursery schoolers the researchers believed that they may simply be guessing. In instances when answering which line is longer became more difficult they may have guessed which would account for the high rates of variability. Another finding of their study was that with the modified Ponzo Illusion the expected increased susceptibility actually declined with age. A flaw they recognized with their experiment was the amount of illusions seen during the same period that possibly created an interaction between them (Hanley and Zerbolio, 1965).
Although these previous experiments seemingly support Leibowitz there are inconsistencies that follow each. The purpose of this experiment will be to see if there is an actual correlation between the age of participants and susceptibility to the Ponzo Illusion. The aim of this research will be to eliminate any extenuating factors that have caused a flaw in previous studies. The first step in our method will be the utilization of a computer for presenting the illusion to participants. The use of computers allows future replications to take place as well as assist in standardizing the results received. A second change will be to only show a classical version of the Ponzo Illusion. Other Ponzo Illusions used modified illusions that consisted of circles and squares and created a filled-space illusion for participants (Yamagami, 2007). By sticking with the classical illusion the threat of filled-space illusion will be eliminated. The independent variable will be the age of the participants and the dependent variable the difference between the upper and lower lines. The hypothesis for this experiment is that the older the participants age the less susceptible they will be to the Ponzo Illusion.
Participants
We ran 25 participants, 15 women and 10 males, and they all were African American. The average age of participants was twenty one. We recruited participants from a Research Methods class. Each individual who participate in the study received class credit and gained research experience.
Apparatus
For this experiment a thirty inch Toshiba computer was used to record the data. Participants were asked to use to the mouse to complete the study. The experiment involved one session, which lasted about 25 minutes to complete. Participants were presented with two black and white horizontal lines, located in the center of the screen. The two stimuli were: two horizontal lines against a plain background or with a set of converging lines, 15 trials were completed.

Procedure
Participants were seated in front of a desktop computer. The experiment took place on Georgia Southern’s campus, Brannen Building in room 2036. Online Psych lab, a well-developed program was used to record the data of participants. Before starting the study the experimenter read a consent form, informing the participants of the study being conducted. To reduce biases, participants input there gender and age only into the program.
A practice trial was presented at the start of the study. Participants were presented with two horizontal lines and asked to drag the line to match the existing line. Next, participants were presented with two horizontal lines; either against a plain background or with a set of converging lines. They were to then use the mouse and adjust the bottom line until it was perceived to be equal in length to the above line. Once the trails were complete participants were debriefed and their name and eagle id was written down for them to receive course credit.

References
Granrud C.
E, Kavsek M. (2012).Children's and adults' size estimates at near and far distances: a test of the perceptual learning theory of size constancy development. Iperception 3, 459– 466
Hanley, C., & Zerbolio, D. (1965). Developmental Changes In Five Illusions Measured By The Up-And-Down Method. Child Development, 437-452.
Parrish, M., Lundy, R., & Leibowitz, H. (1969). Effect of hypnotic age regression on the magnitude of the Ponzo and Poggendorff illusions. Journal of Abnormal Psychology, 74(6), 693-698.
Wagner, D. (1977). Ontogeny of the Ponzo Illusion: Effects of Age, Schooling, and Environment. International Journal of Psychology, 12(3), 161-176.
Yamagami, A. (2007). The Effect Of Frame Figure Type And Frame Size On The Line And The Circle Ponzo Illusions. Japanese Psychological Research, 49(1),
20-32.