Rod and frame test: Difference between revisions

Revision as of 07:29, 9 May 2014

Revision as of 07:32, 9 May 2014

Line 5:

The rod and frame illusion occurs because of the effect of the orientation of the frame on the rod. In the simplest example of the rod and frame illusion, the illusion will cause the participant to perceive the rod to be oriented congruent with the orientation of the frame.<ref name=Corbett>Corbett and Ennis, 2006</ref> When the participant is viewing the rod and frame that are both positioned at 0 degrees (or vertical), he or she perceives the rod as vertical with perfect accuracy. However, when the frame is tilted away from vertical the participant’s perception of vertical is affected. The participant tends to perceive the rod to be tilted in the same direction as the frame is oriented (e.g. if the frame is tilted in the counterclockwise direction the rod will also be perceived as being tilted counterclockwise). As the tilt of the frame increases, the participants’ perceived vertical increasingly deviates from true vertical.

==Rod and Frame Test==

To perform the rod and frame task, an apparatus consisting of a rod in a square frame is used. An example commercial apparatus can be seen in Picturepicture 1. When the participant is being tested using the apparatus, his/hertheir head is setfastened firmly in the chin rest, whichto canprevent bethe seenparticipant infrom Picturecollecting 2visual cues from outside of the apparatus. The rod and frame are shown in the center of the far end of the apparatus (as seen in Picture 3), which provides a [[frame of reference]] to the participant. Both the participant and the experimenter are able to adjust the orientation of the rod, while only the experimenter can adjust the frame orientation by using the appropriate knobs on the apparatus, as seen in Picturepicture 12. The experimenter is able to see the exact degree measurement of the rod and frame from vertical (as shown in Picture 4), while the participant sees the physical rod and frame inside the apparatus.

The methods of constant stimuli, limits, and adjustment can be used to test the participants, but method of limits is most commonly used in research conducted using the rod and frame task.<ref name=Wenderoth>Wenderoth, 1977</ref> When using the method of limits the experimenter sets the orientation of the rod and frame separately and then the participant is asked to adjust the rod orientation until they perceive it to be vertical. Deviation from true vertical can then be determined. Based on which way the frame is tilted, the rod can be viewed as either being tilted in the same direction as the frame (direct effect), or in the opposite direction of the frame (indirect effect).

==Evidence==