Muller Essay

Abstract

This study examined the strengths of Muller-Lyer illusion when participants’ global and local processing were biased using mood induction via music exposure. Participants (N = 426) were randomly divided into global, local and control groups. The global and local groups listened to a predetermined happy and sad music one minute before and throughout the experiment. Afterward, participants completed the Muller-Lyer experiment by adjusting the length of the lines without fins to match the length of lines with fins. A non-significant result was found, indicating that the differences in the strengths of Muller-Lyer illusion amongst the three groups were not significant regardless of mood induction. This may be due to individual differences

According to Gregory (1963), this illusion can be due to misapplied size constancy whereby individuals experience depth cue confusion between an interior and exterior room corner. However, Day (1989) opposed this theory and proposed the theory of conflicting cues whereby our perception of the line lengths area are influenced by the actual length of the lines (local feature) and the overall length of the lines (global feature). He argued that this conflicting cues lead to a compromise causing the overall distance between apices and fins to look longer on the lines with fins-out (Day, 1989). Aside from Gregory and Day, Navon (1977) explained the Muller-Lyer illusion using hierarchical letters (Navon Stimuli), whereby larger letters made up of smaller letters were presented to participants to identify the extent of global and local processing biases. In this case, perceptual global processing occurred when individuals were instructed to pay attention to global stimulus, such as the large shape of letters, and perceptual local processing was attained when individuals were instructed to attend to smaller letters (Navon, 1977; Kimchi & Palmer. 1982). With regards to this, Mundy (2014) used Navon Stimuli to test Day’s hypothesis which stated that

Beforehand, the participants were randomly divided into global, local and control groups based on their birth months. Participants assigned to global and local groups listened to the predetermined happy and sad music for one minute before and throughout the experiment. In contrast, the control group began the experiment without listening to any songs. Two sets of 11 trials were conducted whereby participants were presented with two lines, one with fins, and one without. The angles between the arrow-head of the lines varied from 15 degrees to 165 degrees, with angles from 15 to 75 degrees creating a “fins in” stimuli, while angles from 105 to 165 degrees creating a “fins out” stimuli (McCarthy, n.d). Participants adjusted the length of lines without fins so that it has a perceptual match with the lines with fins using a slider that can be dragged using a computer mouse. In total, the experiment took approximately 15 minutes to complete. Afterwards, the mean adjustment error which is difference in length between illusory and adjusted lines were calculated to show the magnitude of Muller-Lyer