Eye Blinks and Eye Movements in Cognition Psych 230 Lab Manual Professor Jeremy Loebach and Professor Howard Thorsheim 1

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1 Eye Blinks and Eye Movements in Cognition Psych 230 Lab Manual Professor Jeremy Loebach and Professor Howard Thorsheim 1 Reading: Smilek, D., Carriere, S. A., & Cheyne, J. A. (2010). Out of mind, out of sight: Eye blinking as indicator and embodiment of mind wandering. Psychological Science OnlineFirst. DOI: / Objectives To investigate the relationship between eye blinks and eye movements and attention. To introduce you to psychophysiology, specifically electrooculogram (EOG), and its use in psychological science. To investigate the relationship between types of eye blinks and eye movements, and the time at which they occur during reading. To suggest ideas for your Design A Lab project. Terms Canthus (plural = canthi), Dipole, Electrooculogram (EOG), Extra-ocular, Fixation point, Inferior vs. Superior, Lateral vs. Medial, Line change, Oblique, Rectus, Reflex, Saccade Introduction Eye blinks and eye movements are naturally occurring behaviors that interrupt our moment-to-moment visual perception of the world. Yet, most people do not become consciously aware of any perceptual change during these events. However, in those moments when your eyes are in motion (in the case of saccades) or closed (in the case of eye blinks) your brain is actively suppressing information from your eyes rendering you functionally blind. Additionally, both eye blinks and eye movements provide information about what someone is paying attention to. Current theories suggest that both eye blinks and eye movements play a significant role in the processing of information by the brain, and therefore have a strong influence on cognition. An open empirical question is how exactly they play such a role, which we will explore in this lab. The reason people blink their eyes is not as simple as you may think. Orchard & Stern (1991) identify three types of eye blinks. Reflex blinks are instinctive responses that guard the eyes against dust and debris, and are part of the startle response to loud noises. These blinks are generally high amplitude medium duration events (Fig 1). The blink reflex can be classically conditioned to a neutral stimulus such as a tone, which can be demonstrated easily in class. After several pairings of a tone and eye blink, the tone itself will generate the blink. Voluntary blinks are under conscious control and include squinting and winking. These blinks are usually medium amplitude long duration events (Fig 1). Applications of voluntary blinking include their use as control signals for communicating when diseases have made other forms of communication difficult or impossible (such as Multiple Sclerosis, Muscular Dystrophy, or Alzheimer's Disease). Endogenous blinks occur during reading or speaking and reflect changes of attention and 1 Minor revisions Fall 2014 by Prof. Chuck Huff Partial Support was provided for this project by the National Science Foundation to the St. Olaf College Department of Psychology, under Course, Curriculum and Laboratory Improvement Grants DUE and UE , to adapt and implement exemplary laboratory practices and materials for investigative psychophysiology laboratory experiences.

2 Eye blinks and Eye Movements in Cognition 2 changes in thought processes. These blinks are usually low amplitude and short duration events (Fig 1). The more attention required by a task, the fewer endogenous blinks occur. Think about it 1: Some studies have demonstrated that people blink less when they are lying. Do you think that eye blink rate could be used as a type of lie detector? Figure 1. Actual Electrooculogram (EOG) containing voluntary, endogenous and startle blinks. Think about it 2: Think about that for a moment for milliseconds you lose all information about the visual world. Do you even notice? An interesting empirical question is in regards to the specific instant at which blinks occur during visual attention. Research is quite clear that blinks do not occur randomly during reading. Thus, an important and useful question of interest relates to when eye blinks occur depending on what one is reading (e.g., content, difficulty, etc.). Think about it 3: Why would such eye blinks need to be ordered rather than random? Eye Movements The second behavior studied in today s lab is eye movements. The fact that both eyes move and work together is a remarkable achievement, particularly since the two eyes are not connected mechanically in any way! Eye movements are controlled by the brain via the extra-ocular muscles that attach to the outside of the eyeballthere are three pairs of extra-ocular muscles that work together to control each eyeball, and the two eyeballs together operate in tandem. The Lateral and Medial Rectus control side-to-side movement by pulling the eye towards the temple (LR) or nose (MR). The Superior and Inferior Rectus control up and down movement by pulling the eye towards the forehead (SR) or cheek (IR). The Superior Oblique rolls the eye outward to focus on distant objects, while the Inferior Oblique rolls the eye inward to focus on nearby objects.

3 Eye blinks and Eye Movements in Cognition Figure 2. Muscles of the eye (Patrick J. Lynch, medical illustrator; C. Carl Jaffe, MD, cardiologist, 2006). Try it: Movement of the obliques may be hard to pin down. Try crossing your eyes to look at the tip of your nose. Do your eyes feel like they are rolling inwards? Efficient readers move their eyes in a rather complex way and not simply at a constant speed across the page. Rather, readers make small movements of the eye (saccades) when they move from one point of fixation on a page to another. Movements from one word to the next are called forward saccades, while movements back to reread or fixate on a wrod on the same line are called regressive saccades (such as when you read back to find the spelling error in the above line). Saccades from one line to the next allow the reader to sweep to beginning of the next line. When readers stop because they wish to pay attention to a certain portion of the text, this is called a fixation pause. Eye movements and fixation patterns during reading reveal a great deal about the cognitive processes involved in reading and will be explored during today s lab. Think about it 4: Studies routinely show that people with dyslexia have abnormal patterns of eye movements during reading. For dyslexics, saccades tend to be shorter in distance, fixation pauses tend to be longer in duration and they tend to make more regressive saccades overall compared to individuals without dyslexia (Rayner, 1998). Does this mean that dyslexia is caused by abnormal patterns of eye movements? Could dyslexia be treated by teaching people to move their eyes differently? Figure 3. Stylized sketch of typical eye movements during reading three lines of text. 3

4 Eye blinks and Eye Movements in Cognition 4 The measurement of eyeball movement during reading and the visual tracking of a target is called electrooculography (EOG). These EOG signals are created by the fact that the rear (posterior) of the eyeball is negative relative to the front (anterior) of the eyeball, setting up a dipole. Electrodes placed above and below one eye pick up the vertical movement of the dipole (y-axis), while electrodes placed on the right and left canthi measure the side-to-side movement of the dipole (x-axis) yielding a measurement of direction of gaze, as well as the length of fixation in an X-Y Cartesian coordinate system (Figure 4). looking one direction looking straight ahead looking other direction E l e c t r o o c u l o g r a m + looking far in other direction long fixation short fixation 0 time looking straight ahead - Figure 4. Typical EOG recordings during casual eye movements Think about it 5: Right now you may be wondering Why do we need to use such an expensive piece of equipment to track eye movements when we can watch someone move their eyes? Earlier, we mentioned that saccades last between milliseconds, and most people don't realize that they are making them in the first place. Do you think you could count them yourself?

5 Pendulum: Can be made by attaching any object (i.e. 50 gm force calibration weight) to approx. 61 cm (24 inches) of string. Eye blinks and Eye Movements in Cognition Pen or other real object for vertical tracking 5 Passages for reading: Passage 1 easily understandable (i.e., entertainment article) Method Passage 2 challenging material (i.e., scientific article) Note You A sample will work reading in passage three-person in printable groups. PDF format Researcher is available A will in the be lesson the source Help menu. of data (the Participant). Biopac Student Researcher Lab System: B BSL will 4 software, be engaged MP36, in MP35 running or MP45 the BIOPAC hardware and recording observations. Computer Researcher System (Windows C will 7, Vista, present XP, stimuli, Mac OS X and 10.5 make 10.7) notes of what is being done. IV. EXPERIMENTAL Then roles will be switched. METHODS A will be B, B will be C, and C will be A. Do this until all members have been the Participant. All three members of the triad will share their other A. SETUP observations, notes, and data with each other to inform their lab notes. The eye blink data from the EASY TEXT HARD TEXT task will be pooled from all triads. FAST TRACK Setup Detailed Explanation of Setup Steps 1. Turn Apparatus the computer and ON. Materials If Biopac using an MP36 MP36/35 Workstation unit, turn it OFF. If Alcohol-acetone using an MP45, make Prep sure Pads USB cable is connected Non-latex and gloves Ready light is ON. 2. Plug Printed the Electrode copies Lead of text Sets material (SS2L) in to as be read follows: Biopac Lesson 10 EOG 1 Horizontal lead CH 1 Biopac Electrode Lead Set (SS2L - 2 sets) Disposable Vertical lead Electrodes CH 2 (6 per person) 3. Turn ON the MP36/35 unit. Activity I: Data Collection Note that underlined items are suggestions that you make observations that you should record in your lab notebook. Your lab notebook should also include any deviations or revisions you make in procedure or other observations you make about the materials, procedure, or data. Page P-1 Optional: BIOPAC Adhesive Tape (TAPE 2) use to tape wires to reduce cable strain Objective You will explore eye movements and eye blinks while reading an easy and hard passage. In addition, you will use the information from the workstation to calculate your results. Before you start making recordings, coordinate with your team what Setup you continues are going to be looking for. Fig MP3X (top) and MP45 (bottom) equipment connections Procedure Set up and calibration 1. Make sure Biopac MP36 unit is OFF (back), that is, no green lights are on (front). 2. Plug electrode leads into the MP36. Horizontal is channel 1 and vertical is Turn on MP36 using the switch at the rear of the box. 4. Always wear non-latex gloves when working with participant 5. Clean the skin with alcohol pads where the electrodes will be placed. Important: squeeze out 3 drops of alcohol before using to prevent alcohol running into eyes!! 6. Attach 6 electrodes as shown in diagram on screen and below. For accurate recordings, attach the electrodes so they are horizontally and vertically aligned. Page P-2 L10 EOG-I Biopac Student Lab 4 4. Gently clean and abrade skin. 5. Attach six electrodes to Subject s face as shown in Fig IMPORTANT For accurate recordings, attach the electrodes so they are horizontally and vertically aligned. Fig Proper electrode placement If the skin is oily, clean electrode sites with soap and water or alcohol before abrading. If electrode is dry, apply a drop of gel. Attach one electrode above the right eye and one below, such that they are aligned vertically. Attach one electrode to the right of the right eye and one to the left of the left eye, so they align horizontally. The other two electrodes are for ground, and alignment is not critical. BIOPAC Systems, Inc,

6 minutes abrading. before start of Calibration. 6. Clip CH 1 Electrode Lead Set (SS2L) in the If electrode is dry, apply a drop Drape the electrode lead cables horizontal placement, following the color of gel. behind the ears, as shown, to code (Fig. 10.8). give proper cable strain relief. Eye blinks and Eye Movements in Cognition Attach one electrode above the 6 right eye and one below, such that they are aligned vertically. IMPORTANT For accurate recordings, attach the electrodes so they are horizontally and vertically aligned. Attach one electrode to the 7. Attach the horizontal electrode lead set right (SS2L) of the right from eye and channel one to 1 to electrodes (RED next to their Right eye, WHITE next to the their left of the Left left eye, so they skin. and BLACK above their Fig Proper electrode placement align horizontally. Left eye). Attach vertical electrode lead set (SS2L) from channel 2 to electrodes The other two electrodes are (RED above their Right eye, WHITE for below ground, their and alignment Right is eye, BLACK in the not critical. Middle). Important: Clip lead set to the participants shirt to keep them from For optimal electrode contact, place electrodes pulling. You can use a stocking cap to help Fig. on 10.8 skin keep Horizontal at least five the (CH electrode 1) Lead leads in place. minutes before start of Calibration. 6. Clip CH 1 Electrode Lead Set (SS2L) 7. in Clip the CH 2 Electrode Lead Set (SS2L) in the horizontal placement, following the color vertical placement, following the color code code (Fig. 10.8). (Fig. 10.9). Placement Drape the electrode lead cables behind the ears, as shown, to give proper cable strain relief. Connect the electrode cable clip to a convenient location to help relieve cable strain. Electrodes must lay flat on skin. Connect the electrode cable clip to a convenient location to help relieve cable strain. Electrodes must lay flat on 7. Clip CH 2 Electrode Lead Set (SS2L) in the vertical placement, following the color code (Fig. 10.9). Fig Horizontal (CH 1) Lead 8. Have Participant adjust the seating position such Placement Placement that his/her eyes are approximately at arm s length (have them reach) from center of the monitor. 9. Start BIOPAC Student Lab Program. Choose Lesson L10 Electrooculogram (EOG) I. Type in a file name that all team members will be able to remember (NameDate works quite well). Click on OK. Setup continues 10. Tell Participant not to move his/her head. Click on Calibrate. You will be instructed to move your eyes from extreme left to extreme right and back to center 4 times (Left Right Center x 4) and then from extreme top to extreme bottom 13. Verify recording resembles the example There should be cyclical variation in the Horizontal data and the and back to center 4 times data. (Up Down Center amplitude x 4). should progressively decrease. BIOPAC Systems, Inc L10 EOG-I Page P-7 If similar, click Continue and proceed to the next recording. Identifying simple eye Fig movements: Vertical (CH 2) Lead Tracking moving objects Placement 1.) Left and right movement 11. Tell Participant not to move his/her head. For this step the experimenter should be face participant. Experimenter should hold a pen about 10 in front of Participant s eyes. Important: Participant should pick a Fig. focal Example point Simulated on Pendulum the pen data so Setup continues Fig Vertical (CH 2) Lead If necessary, click Redo. Data would be different for reasons detailed in Step 7. that their eyes remain horizontal. 12. Click on Record Vertical Tracking 13. Experimenter holds the pen still in the center of the Participant s visual field. 14. Prepare for the recording Director holds pen centered with the eyes - adjust as necessary to Then Experimenter briskly Director moves positions the a pen about pen 25 cm laterally (10 10 inches and back to center inches) from Subject. and track its movement WITHOUT moving head. over 3 seconds. Experimenter should also insert a marker (F9 Key on PC Escape Subject tracks pen. on Mac) and type L for Director moving moves pen the vertically pen up and left and indicates R it is out for of view. moving the pen right. down to determine the limits of the Participant should fixate on Subject s the visual pen, range. track it, and try not to blink. and the recording is ready to begin. Review recording steps. 14. Click on Suspend. Identify relationship between pen direction and what you see on the computer. 15. If necessary, click Redo. If data look good click Continue to move to next stage. Click Redo and repeat Steps 8 13 if necessary. Note that when Redo is clicked, the most recent recording will be erased. maintain focus (Fig ). Subject must pick a focal point on the pen Director determines (and mentally notes) the upper and lower edges of the Subject s visual field by moving the pen up and down until Subject Director returns pen to a center position (eyes looking straight ahead) Fig Vertical tracking positioning Recording continues

7 Eye blinks and Eye Movements in Cognition 7 2.) Up and down movement 16. Repeat steps Again, Experimenter should hold the pen stationary in the center of Participant s visual field. Experimenter should briskly move the pen up 10, pause, down to center, pause, further down 10, pause, and return to the center and stop. 18. Click on Suspend. Identify relationship between pen direction and what you see on the computer. 19. If necessary, click Redo. If data look good click Continue to move to next stage. Identifying complex eye movements: Reading 3.) Baseline 20. Experimenter should steadily hold a blank sheet of paper about 12 in front of Participant s eyes in the center of the Participant s visual field. 21. Click on Record 22. Experimenter should insert marker (F9 Key on PC Escape on Mac) and label it baseline. Be sure to mark anything you think would be important to note. 23. Look at the blank sheet for 1 minute. 24. Click on Suspend. Identify relationship between eye movements and the baseline task and count eye blinks during. Record your tally on a sheet of paper. 25. Review data. If data look good, click on Continue. If not click on Redo. 4.) Easy material 26. Experimenter should steadily hold the easy reading material about 12 in front of Participant s eyes in the center of the Participant s visual field. 27. Repeat steps for easy reading material. Identify the relationship between eye movements and reading direction and count eye blinks during the reading time. Record your eye blink tally on a sheet of paper. 28. Review data. If data look good, click on Continue. If not click on Redo. 5.) Hard material 29. Experimenter should steadily hold the hard reading material about 12 in front of Participant s eyes in the center of the Participant s visual field. 30. Repeat steps for hard reading material. Identify the relationship between eye movements and reading direction and count eye blinks during the reading time. Record your eye blink tally on a sheet of paper. 31. Review data. If data look good, click on Done. This will close the file for the individual being recorded. If not click on Redo. 32. When all data (baseline, easy, hard) for one participant are collected, disconnect the participant from the leads. Electrode removal and cleanup should be done at a convenient time during the lab. 33. Partners then rotate, testing one Participant at a time, and collect their data. This means starting over at step When each person s data have been recorded, print out or save electronic copies of all results enough for all three team members. Remember to print in landscape mode. If saving, be sure to save to a flash drive or the shared class folder.

8 Eye blinks and Eye Movements in Cognition 8 Activity II Data collation and analysis The preceptors will now lead you through the procedures needed to bring together all the data so it can be shared among the lab members. For each participant, you will need to calculate two scores to give to the preceptors: a score for the easy reading and a score for the hard reading. To do this, count the ENDOGENOUS blinks during the baseline, easy and hard reading. Do not count voluntary blinks. You will need to establish a criterion for what counts as endogenous. Then, subtract each participant s baseline (BRbaseline) blink rate from his/her blink rates during reading Easy (BREasy) or Hard(BRHard) text, that is: EASY = (BREasy) - (BRbaseline) HARD = (BRHard) - (BRbaseline) NOTE: The difference scores may be positive or negative. They will then lead you through doing and interpreting a t-test to determine if the number of eye blinks in the easy reading condition is different from the number of eye blinks in the hard reading condition. Describe the results from the t-test in the way you might report it in a paper. What do these results mean with regard to the hypothesis that people should blink less when they are under higher cognitive load? Can something you have learned from this lab be used to investigate other issues in psychology? How might that be turned into a lab for this class? Further reading Blanchard, H.E., & Iran-Nejad, A. (1987). Comprehension processes and eye movement patterns in the reading of surprise ending stories. Discourse Processes, 10, The impact of stories that have surprise endings, like O Henry stories, is related to what happens to the eyes at the end of such stories. How interdisciplinary! Charawaza, K., Klin, A., & Volkmar, F. (2003). Automatic attention cueing through eye movement in 2-year-old children with autism. Child Development, 74(4), Children with autism have aberrant eye movement and fixation patterns that some claim can explain some of the social deficits that they may have. Goldstein, R., Bauer, L. O., & Stern, J. A. (1992). Effect of task difficulty and interstimulus interval on blink parameters. International Journal of Psychophysiology, 13, Do people blink more or less when reading difficult or easy materials? Just, M. A., & Carpenter, P. A. (1980). A theory of reading: From eye fixations to comprehension. Psychological Review, 87(4), If you look at something for a long time, will you understand it better? How does your hypothesis compare to what these folks found? A classic.

9 Eye blinks and Eye Movements in Cognition 9 Orchard, L. N. & Stern, J. A. (1991). Blinks as an index of cognitive activity during reading. Integrative Physiological and Behavioral Science, 26(2), Rayner, K. (2009). Eye movements and attention in reading, scene perception, and visual search. Quarterly Journal of Experimental Psychology, 62(8), A comprehensive review of everything eye movement related since the beginning of time. Verschuere, B., Crombez, G., Koster, E.H., Van Bockstaele, B. & De Clercq, A. (2007). Startling secrets: startle eye blink modulation by concealed crime information. Biological Psychology, 76(1-2),