If it's not there, Where is it? Locating illusory conjunctions
There are times when I can swear by God's name that I saw someone weird pass by the corridor or someone wearing a weird-looking hat. When i take a second glance at the exact place, though, the person or the thing cannot be found. Instead, it appears to have split between two other persons in different locations halfway from which I thought I saw the first weird-looking person. I learned later on in class that this is phenomenon is called as illusory conjunction. Goldstein (2010) defined illusory conjunction as an illusory combination of features that are perceived when stimuli containing a number of features are presented briefly and under the conditions in which focused attention is difficult . Like the time when i was walking down the corridor.
There has been studies conducted that complex objects are decomposed by the visual system in features such as color and shape. One such study is that of Hazeltine, et al (1997) where they analyze the perceived location of illusory conjunctions to know the roles of color and shape in the location of visual objects. It was initially hypothesized that the perceived location of an object is determined by a single feature but this experiment was able to debunk it.
In the experiment, the researchers used two features, the Letter O and the color green. The participants were asked to indicate where the letter O appeared on the screen and whether it was green. An identical fixation cross and an identical mask were used. The duration of the stimuli varied from 57 to 143 ms. When the participants perceived that the letter O was green, they pressed the left button on that part of the screen and when they perceived that the letter O was not green, they pressed the right button. Fifteen college students from the University of California were recruited for the study.
They confined the analysis of perceived locations to trials in which the target was not green but one of the letters immediately next to it was. The experiment demonstrated that the distribution of the illusory conjunctions did not result from sampling one location in each trial from one of two distributions—one centered at the letter position and the other centered at the color position. Instead, the perceived location was a combination of information from both the color and the letter.
The study was really composed of four experiments, one of which just attempted to replicate the results. The other two just proved that both color and form influence illusory conjunctions. The experiment I used in this article was the third one which I think is the more salient among the four. Although the study consists of only a very few sample per experiment, validity was assured by the consistency of the results and the replication of the study by the fourth experiment.
This study actually made me think of court trials and witnesses in a case. What if they didn't actually see what they thought they saw at a particular location? This tells us that we must not always trust our senses and we should take a second glance before affirming that we witnessed something. And this is also why we must not believe in love at first sight. Who knows? Maybe it's just illusory conjunction and the guy who passed by does not really have both a pretty face and a great body. XD
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Sources:
Goldstein, E. B. (2010). Sensation and perception (8th ed.). California, USA: Wadsworth.
Hazeltine, R. E., Prinzmetal, W., Elliott, K., (1997). If It's Not There, Where Is It? Locating Illusory Conjunctions. Journal of Experimental Psychology, 23, 1, 263-277. Retrieved from EBSCOhost.
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