The overall goal of this procedure is to record eye movements during reading. This is accomplished by first positioning eye tracking equipment so that the eye is clearly visible when the subject looks at the display monitor. The second step is to calibrate the software to accurately record movements of the eye.
The third step is to display the passages to be read. The final step is to evaluate the duration and pattern of fixations on words in the passages. Ultimately, the eye movement data can be used to determine the difficulty of processing individual words and phrases, and make inferences about the cognitive processes involved in reading.
The main advantage of the eye tracking method over other methods, such as presenting sentences one at a time, and measuring reading time for each sentence is that eye tracking provides a natural measure of reading behavior that shows the moment by moment changes in processing difficulty as a reader moves through a text. This method can help answer key questions in the text comprehension field, such as understanding how figurative phrases are read and understood. This method can provide insight into the cognitive processes involved in reading.
It can also be applied to research using images such as what draws a person's attention in an advertisement. To begin position, the iLink system, which consists of both an infrared light source and a video camera beneath the monitor that will be used to display the stimuli, then instruct the subject to adjust the seat height to a comfortable position while keeping the chin in the chin rest and forehead against the forehead.Rest. For this particular monitor size, the subject should be seated approximately 60 centimeters from the display monitor.
Once the subject is comfortable, present information on the subject's monitor describing the setup and operation of the eye tracker system. The system tracks eye movements accurate to 0.5 degrees by measuring changes in pupil position in a digitized video image. Begin by focusing the camera to ensure optimal imaging and tracking.
Ensure that only one eye is visible in the camera's display to prevent the eye tracker from accidentally shifting to the other eye. After a head movement, adjust the infrared sensitivity threshold of the video camera. At this point, the eye tracker should detect the pupil and corneal reflection and begin tracking the subject's eye position.
Next, instruct the subject to look at each corner of the computer monitor to ensure that the pupil and corneal reflection are being tracked across the entire surface of the display. Prepare for calibration by instructing the subject to fixate upon each dot until it disappears. Tell the subject not to attempt to predict the dots.Movements.
Calibrate the eye tracking software by recording eye position while the subject fixates on a set of nine fixation points displayed on the monitor at known locations. Next, validate calibrations by instructing the subject to fixate on the same nine points as during calibration. If the average degree of error exceeds a half degree of visual angle, recheck the alignment of the eye tracker and repeat the calibration process.
After instructing the subject to refrain from talking or making other head movements, begin the experiment with a small number of practice trials. Before each trial instruct the subject to fixate on the drift correction point, which is displayed where the first word of the text will be presented. Instruct the subject to read at a normal rate for comprehension and to press a button on a response pad when they finish reading each passage.
After completing the practice trials, ask the subject if there are any questions. Then continue with the experiment by presenting the passages to be read. The subject controls the time between reading passages and can take breaks as needed.
After completing the experiment, debrief the subject by handing them an IRB approved debriefing form that describes the purpose of the research shown. Here are eye movements from a sample passage containing an unfamiliar metaphor.Four. The extra processing difficulty increases the density of fixations represented by blue circles.
Larger circles indicate longer duration.Fixations. This analysis found a regressive secod from the word doorway to the word degree. This graph shows total fixation duration for words in familiar and unfamiliar metaphors.
The results demonstrate that more time was generally spent processing words in unfamiliar metaphors than in familiar metaphors. Once mastered, setting up and calibrating the eye tracker can be done in five to 10 minutes if performed properly. While attempting this procedure, it's important to continually monitor the accuracy of the calibration and recalibrate as needed.
This technique paved the way for researchers to explore the online processing of texts such as which aspects of a text affect, recall, and how words are put together to form the overall meaning of sentences.
