Cognitive Studies/Psychology/Visual Studies 201:
COGNITIVE SCIENCE IN CONTEXT

Effects of Cell Phone Use on Driving Performance: Investigating the Mechanism of Interference

Laboratory Module (Spring Version)

by Leon Rozenblit
Department of Psychology, Cornell University
(now at Yale University, leonid.rozenblit@yale.edu)
Edited and updated by Doug Elrod

  1. INTRODUCTION
    1. BACKGROUND SIGNIFICANCE
    2. A BRIEF REVIEW OF THE LITERATURE ON DRIVING PERFORMANCE AND TELEPHONING -- SOME FACTORS TO CONSIDER
    3. EXAMPLE: A TENTATIVE TWO FACTOR MODEL OF INTERFERENCE
  2. EQUIPMENT
    1. DRIVING SIMULATOR
    2. MACINTOSH COMPUTERS
    3. CORDLESS PHONES
    4. EYE-TRACKER
  3. LABORATORY EXERCISES
    1. MEASURING THE EXTENT OF TELEPHONING INTERFERENCE WITH DRIVING
    2. EFFECTS OF CONVERSATION CONTENT
  4. FINAL LABORATORY REPORT FOR THE DRIVING MODULE

    Appendix A: Data Analysis

    Appendix B: Scenario Editing Instructions

  5. BIBLIOGRAPHY
    1. BOOKS AND CHAPTERS
    2. ARTICLES SPECIFICALLY RELEVANT TO DRIVING AND TELEPHONING

I. Introduction

A. Background Significance

The national media has recently focused on the alleged increased driving risk created by the use of cellular telephones. The popular press has reported a four-fold increase in risk of automobile accidents to individuals who use cellular phones while driving. The radio program, "Car Talk", has addressed the issue, and has compiled a large number of resources about it on its web site. A recent scientific study suggests that talking more than 50 minutes per month on cellular phones in a vehicle is associated with increased risk of a traffic accident (Violanti & Marshall, 1996). In New York State, the perceived risk of using a cell phone has led to a ban on using hand-held cell phones while driving (see http://www.nysgtsc.state.ny.us/phon-vt.htm for details). Because hands-free cellular phones are excluded from this ban, this module will use phones with headsets. This will allow you to test whether using the phones in the legal way results in any driving impairment, even though one is not holding the phone while driving.

Are cellular phones really a road menace? While cognitive science may not be in the position to resolve the critical public policy issues involved in the debate (e.g., the value of mobile phone use versus the cost of increased risk to life and property), it may shed light on this exciting controversy by investigating several questions: Why is talking on the phone while driving dangerous? Is it any more dangerous than talking to a passenger while driving? If so, why? How does varying the content of conversation and familiarity with equipment effect driving performance? What do the results tell us about the cognitive processes involved? By explicating the mechanism of interference, cognitive science may be able to identify especially dangerous driving situations, as well as conditions that allow drivers to talk on the cellular phone without significantly increasing the risk of accidents.

In this laboratory module you will investigate these exciting and socially relevant questions. You will use several tools to help with the investigation. First, you will use the STISIM driving simulator designed to emulate actual driving conditions. Second, you will use a portable phone intercom system that approximates the important features of a cellular phone.

Reading Assignment One

Theoretical Background

Cross-modal interference is a basic puzzle in cognitive science. Why and how do tasks performed using two different modalities (here, vision and audition) interfere with one another? While cognitive psychologists are quite accustomed to using patterns of interference to study cognitive mechanisms, the driving-telephoning problem is unusual because the pattern of interference is itself of primary interest. A theory of mechanism, of course, is invaluable in helping us formulate research hypotheses. We will begin by considering why telephoning might interfere with driving. We will attempt to focus our understanding of the interference by considering how other attention-grabbing tasks might interfere with driving.

Discussion

Keep the ideas you have discussed in mind. They will come in handy shortly. Below, we will try to develop a tentative model of a driving-telephoning interference following a brief review of the literature, which points out several factors as important to driving performance under a verbal interference task.

A cognitive model attempts to describe human activities in terms of information processing. A cognitive model begins by considering the informational inputs, and the behavioral outputs of a particular task; the model must then suggest, given the constraints on human information processing, a plausible way in which the individual transforms the informational inputs into the behavioral outputs. A tentative example of a cognitive model is presented in Part B of the Introduction.

B. A Brief Review of the Literature on Driving Performance and Telephoning -- Some Factors to Consider

Several studies suggest that talking on a cellular phone while driving interferes with driving performance (Briem & Hedman, 1995; Brookhuis, de Waard, & Mulder, 1994; Violanti & Marshall, 1996). While the literature on conversational interference with driver behavior is sparse, researchers have identified several factors as important to the degree to which using a cellular phone may interfere with driving:

Discussion

C. Example: A Tentative Two Factor Model of Interference

The brief review of the literature leads me to tentatively propose a two factor model of interference between driving and telephoning: Talking on a cellular phone interferes with driving in two ways. First, conversing increases the cognitive load, and reduces resources available for non-automatic processing. This factor should relate to difficulty of conversation: intense conversations would interfere more with non-automatic tasks than light conversations. Furthermore, conversations can specifically tax cognitive resources involved in driving and navigation. Thus, conversations about navigation (e.g., giving driving directions) would interfere more than conversations about procedures (e.g., giving cooking directions). Also, telephone conversations would interfere with driving more than passenger conversations because the passenger would modulate the cognitive load of the conversation in response to the driving environment; a telephone caller (especially if inexperienced w/ cell phone use) would not.

Second, using the cellular phone places additional demands on the visual system when the driver is required to perform visually-guided manipulation of the phone equipment. This factor would be independent of conversation difficulty, but would vary with driving conditions: operating the telephone equipment would interfere more with driving under difficult driving conditions that require more intensive visual processing than with driving under normal conditions that is not visually intensive. N.B. This tentative model is only offered as an example; feel free to develop your own.

II. Equipment

A. Driving Simulator

Several pieces of equipment will be crucial to completing this module. You will use the STISIM driving simulator, the AT&T cordless phone, and the Macintosh computer on nearly every exercise. It may also be possible for you to use the ISCAN Eye-tracker in an extension of the experiments. Below you will find brief descriptions of the equipment and instructions for operating it.
Simulating driving is no easy task. The STISIM simulator provides accurate car physics at 30 frames per second. It also automates much of the data collection necessary for the exercises below.
STISIM is a software package that can run on Pentium PCs. (Look for the computers with steering wheels in front of them). To simplify the exercises, we have configured STISIM to launch automatically when you start up one of the PCs.

Starting Up

Turn on the PC and wait for the STISIM prompt screen. You will see six options:
  1. Test information.
  2. Run driving simulation.
  3. Atmospheric conditions.
  4. Edit Files.
  5. Shell to DOS.
  6. Quit.
You can select any of the six options by either using the arrow keys on the keyboard and pressing "Enter," or by typing the first letter of each command on your keyboard (e.g., "q" for quit).

Restarting the PC

If you get into any kind of trouble with the software, the first thing to try is to abort the simulation using the ALT-F1 keys (hold down the ALT key and tap the F1 key). If this doesn't work, you can restart the PC by pressing the restart button (either the middle of the three buttons on the front of the PC, or one near the top marked "Restart"). You can also restart (as a last resort) by turning the power off and then back on. The power button is the rightmost of the three buttons on the front of the PC (or near the top on the right).

Starting Up the Simulator Without Restarting the PC

Should you need to run STISIM without restarting the PC, you only need a little more information. The six-command prompt-screen is displayed by a small utility program called SIMMASTR. SIMMASTR is located in the STISIM directory on your hard drive.

To get to the prompt screen from the DOS prompt (that is, if you accidentally quit the program and find yourself staring at something like this: "C:>") type the following commands:

CD \STISIM [takes you to the STISIM directory]
SIMMASTR [runs the utility program]

Turning on the Speakers

Move the speakers close to the driver. Press the power button on the external speakers, if they have one. The red "on" LED should go on. Adjust the volume control knob on the speaker so that the indicator arrow is approximately one-third of the way from left to right.

Set Atmospheric Conditions

STISIM lets you set the atmospheric conditions for each trial. The default setting we will use in this module is "Fog." (We will use "Fog" as the default condition because it increases the base rate for accidents to the point where changes in the rate of accidents can be measured in a fairly short experiment. Under normal driving conditions -- in simulations, and in the real world -- accidents are so infrequent that we would have to observe drivers for many hundreds of hours to reliably detect any changes in the accident rate.) MAKE SURE TO CONFIRM THAT THE ATMOSPHERIC CONDITION IS SET APPROPRIATELY BEFORE BEGINNING A TRIAL.

To change the atmospheric conditions, select "Atmospheric conditions" from the main prompt menu. Remember, you can do this using either the arrow keys or by pressing the "a" key. Now, select the option most appropriate to your experiment.

Provide Test Information

The first thing you will want to do is carefully enter the Test Information for each trial. Be very careful here: STISIM uses some of the information you provide (the Patient [Subject] number and the run number) to name the data file. You may want to write down the Patient [subject] numbers you assign each subject.

If you need to correct a Test Information entry before moving to another field, the Backspace key on the keyboard will move you to the left on a line and erase as it moves. The left and right arrows on the keyboard will move you left and right on a line without erasing. After you have finished entering the information for one field, move down from that field to the field below, e.g., from Patient Name to Patient Number, by pressing the Enter key on the keyboard.

To record the subject's test information, first select "Test Information" from the main menu (remember, you can do this using either the arrow keys or by pressing the "t" key). STISIM should enter the date and time automatically. Just press Enter. Next, type the subject's name (in the quaintly named "patient's name" field), the subject number in the "Patient code" field (each subject should have a unique subject number assigned to them), and a run number. Be very careful not to mistype the subject's name, and to use exactly the same name for the subject from trial to trial. For consistency, use three-digit subject numbers (e.g., 101, 102, 111).

Note, STISIM will try to guess the correct subject number and run number for each subject by looking at the data files already present in the SIMDATA directory; it's usually accurate, but you must be the final judge.

Finally, fill in the "comments" field. Here, you should provide information that will make this run easy to identify in the subsequent data analysis. You should clearly note the exercise number, the condition (e.g., no conversation, light conversation, heavy conversation), and any additional subject information you believe may be useful (e.g., driver's experience).

If you make a mistake filling out the subject test information, you can always press F9, and start over. To record the test information and proceed, press F10.

Driving

First, make sure the driver is in a comfortable position, facing the screen, and can naturally manipulate all the driving controls. Ensure that the steering assembly is securely fastened to the desk.

Now select "Run driving simulation" from the main prompt menu. Select either "Urban" or "Suburban" (following the specific instructions for your experiment) from the next menu. STISIM will ask for a scenario number. We have created several driving scenarios to reduce any learning effect of repetition.

You will be using one of the following scenarios in the first experiment:

Suburban 11 (practice)
Suburban 21 (first run)
Suburban 31 (second run)

Urban 12 (practice)
Urban 22 (first run)
Urban 32 (second run)

To run the scenarios, follow the instructions on the blue screen. The last instruction tells you to "press the right button" when you are ready to begin. Unfortunately, this last instruction is misleading -- you don't need to press any buttons. Instead, when you are ready to begin driving, lightly push the shift lever on the steering assembly forward.

That's it! You're on your way!

Note: Before beginning the experiments, the subject should "warm up" by driving through at least one Urban and one Suburban scenario. (Try Urban and Suburban scenarios 01 through 06) Make sure you clearly label the data generated by the warm-up exercises so as not to confuse them with the real data. (I recommend assigning all warm-up exercises the Patient code "000," and typing "Warm Up" in the name field).

Saving Your Data

STISIM will automatically save your data-file in the SIMDATA directory on your hard drive. To analyze the data, you will save the data-file to a 3.5" diskette, and move it to a Macintosh computer where you will import the data-file into Microsoft Excel.

How Are the Data Files Named?

STISIM names data files automatically and saves them in the SIMDATA directory. The first 3 digits of the filename are the subject number (a.k.a. the "patient number") The last 2 digits are the run number. The data summary file for run #3 by subject #112 would be named something like
1120003.SUM.
There will be another, much larger, file named
1120003.DAT.
You may ignore this file for our present purposes (It contains second-by-second records of the driver's performance). What information do the data files contain? The summary files contain five blocks of data.
  1. Test information: The first block from the top contains the test information you entered at the beginning of the run.
  2. Divided attention data: you will not be using this information during the exercises.
  3. Driver performance data: you will use some information in this block to determine how closely a driver came to colliding with another car during the run.
  4. Driver mistakes: a count of the mistakes the driver made during the run, with different types of mistakes tabulated separately.
  5. Individual mistakes: a record of the time and the coordinates of each mistake the driver made during the simulation run.
You will use Excel to "clean up" the summary file data, and to compute a performance score for each run. (See instructions below.)
Note: you should save your data-files to a diskette and transfer them to a Mac-compatible at the end of each session. The files in the SIMDATA directory will be regularly deleted to make room for new subjects. I strongly recommend keeping multiple copies of your hard-won data. Back up! Back up twice! Yes, it's a pain, but not the same intensity of pain as losing 40 hours of work because of a disk error. Either use a second floppy disk or copy from your floppy disk to your Zip disk on a Mac or Mac-compatible.
Also note that the STISIM program has an error that calls each scenario number "0" inside the data file. So, Suburban 11 will say "Suburban #0" in the data file. You should correct this before you forget which scenario you used for the data file.

Moving the Data Files to a Mac-Compatible

At the end of your run you will see a summary screen. Press the "escape" key on your keyboard to leave the summary screen, and proceed as follows:
  1. Quit STISIM.
  2. Type CD SIMDATA
    (this puts you in the directory where your data were saved)
  3. Insert your 3.5" diskette into the floppy drive.
  4. For each datafile "filename.ext", type
    COPY filename.ext A:
OK, we're done with the hard part. Now you can eject the diskette, carry it over to the Macintosh-compatible computer you'll be using, insert the diskette into the floppy drive, and copy the data files to your Zip disk. Then either make another copy on a second floppy disk or temporarily copy the data files onto the Mac-compatible's hard drive and then onto a second Zip disk (Remember, there is no permanent personal file storage on the laboratory's Mac-compatibles. The hard drives will regularly be purged of all personal files).

Cleaning Up Your Data File with Excel

Excel can open the data files. I recommend saving all your cleaned-up data in a large Excel Workbook. On-line help for Excel is excellent, and easily available.

If you are unfamiliar with Excel, now is a good time to get a feel for it. On the Mac-compatible, open Excel (you can select Excel form the Microsoft Office menu at the top of the screen). Once Excel has launched, select Quick Preview from the Help menu (the yellow balloon with a question mark -- second icon from the right on the menu bar). When you are done with the Preview, select Examples and Demos (at least the first 7 topics). A complete on-line manual is also available (in the Microsoft Office folder). You may find the first few chapters quite useful.

To clean up the summary data files with Excel:

1. Make a copy of the data file on the hard drive (or your Zip disk)
2. Launch Excel.
3. Select Open from the file menu.
4. Navigate to the data file you wish to open.
5. Click the Open button -- this will bring up the Text Import Wizard window.
5.1. In the Step 1 window, make sure:
5.1.1. Original Data Type is set to "Fixed Width."
5.1.2. Start Import row is set to 1.
5.1.3. File Origin is set to DOS.
5.1.4. Click the Next button.
5.2. In the Step 2 window:
5.2.1. Delete the three left-most break lines (by double-clicking on them). The two rightmost lines should remain unchanged.
5.2.2. Click the Next button.
5.3. In the Step 3 window, click the Finish button.
6. Excel will now create a new document (a workbook) with the data imported from the summary file. In the new workbook:
6.1. Increase the column width of Column A so that you can see all the text in the column. (You can increase the width by clicking on the column divider and dragging right.)
6.2. You will notice that the last block of data (Individual Mistakes block) is "lumped" into a single column. You will organize the data into multiple columns:
6.2.1. Select all the Individual Mistakes cells in Column A (i.e., the cells with the text and two sets of numbers in them).
6.2.2. Select Text to Columns from the Data menu.
6.2.3. Click Next on the first two windows of the Text to Columns Wizard, and Finish on the last window. The data is now in a row/column format.
6.3. Format the data to match the Example worksheet:
6.3.1. Open your copy of the Driving Raw Data DB workbook.
6.3.2. The very first worksheet in the workbook is called "Example." Format your data to look like the first three columns of the Example worksheet.
6.3.3. Delete extraneous information. For example, we have not collected any divided attention data; therefore you should delete the Divided Attention block:
6.3.3.1. Select the rows of the Divided Attention Data.
6.3.3.2. Choose Delete from the Edit menu.
6.3.4. Use the Insert and Edit menus to insert and delete rows, as necessary. (As a check, make sure that "Mean time to collision" line is in row 28, the "Off-road Accidents" line is in row 33, and the "Length of Run" line is in row 40.)
7. Insert a new worksheet into your copy of Driving Raw Data DB.
8. Copy the cleaned up summary data into the new worksheet.
9. Rename the worksheet using the subject number and run number for identification. (The STISIM file name will work nicely -- just be consistent.)
10. Now, copy the computational formulas in columns E and F of the Example worksheet (outlined by a heavy box) into the matching location on the new worksheet. If everything worked, the computational formulas should yield a performance score in cell F4.
Don't forget to save the new version of the workbook. For guidance on data analysis, please see the Data Analysis Appendix [when available], and class handouts.

Note: you can probably save some time by hand-copying the information on the blue summary screen into your lab notebook, and then typing it into the your personalized Excel Driving Raw Data DB.

B. Macintosh Computers

The lab is equipped with state-of-the art Macintosh-compatible computers running the Mac OS. You should familiarize yourself with the operating system and the applications you will be using. Specifically, you should become familiar with Microsoft Excel and StatView. You will use both of these programs to manipulate and analyze your data. A sample Excel Workbook for data storage has been created for your use. You can find it in the Driving Module folder on the Mac-compatibles. To use the sample workbook as the basis for your own workbook:
  1. Open the Excel file called "DrivingDataBook template".
  2. Choose Save As from the File menu.
  3. Save on your Zip Disk as DrivingDB.YOURNAME.

C. Cordless Phones

You will use AT&T cordless telephones to simulate cellular telephones. These phones come in pairs, which can talk to each other through the air via their "intercom" function (they aren't plugged into a telephone line). Each pair relays its signal through an associated base unit (outside the lab). The signal can reach from the base unit to most places on the second floor where the lab is located, but degrades rapidly after that.

Pressing the Intercom button on either phone causes the other one to ring. Press the Phone button to respond to the call, or hang up the call when you are through. Talk as you normally would on the telephone.

The phones have headsets which plug into the small jack behind the rubber flap on the right side of the phone. You will be using these during the experiments. The headsets work best when the microphone is a couple of inches directly in front of the mouth, and a little below (around the chin).

D. Eye-Tracker

Some of you may have an opportunity to use the ISCAN eye-tracker later. The eye-tracker is a complex piece of equipment; considerable training is required to use it properly. Those of you interested in using the eye-tracker should notify me or the instructor. (Email me at lgr4@cornell.edu.) If resources are available, I may be able to arrange a training session.

III. Laboratory Exercises

Laboratory Exercise One: Measuring the Extent of Telephoning Interference with Driving

Reading Assignment Two

Discussion

Goal

In this laboratory exercise you will attempt to determine whether telephoning interferes with driving and attempt to quantify the extent of the interference. You will proceed by having subjects drive several runs of the STISIM simulator in one of two conditions: (1) no interference, and (2) telephone conversation interference. STISIM will record how many mistakes a driver made in each trial. You will be able to compare the number of mistakes the drivers made during the no interference runs with the number of mistakes they made during the telephone conversation runs.

Note that you must balance the order in which the subjects experience the two conditions to control for any experience-related improvement. (It's possible, for example, that subjects tend to do better on the later runs of the simulator because they have learned how to use the simulated controls over earlier trials. Thus, if you always ran the telephone interference condition trials first, the data would appear to indicate that subjects drove better without telephone interference, even if that were not the case.)

You will use a simple method of controlling for order of trials -- half of the subjects will run in the no interference condition first, the other half will run in the interference condition first. A simple way to keep track of who is running what condition in what order is to number subjects consecutively (say starting at #101), and running all the odd-numbered subjects with the non-interference condition first and all the even-numbered subjects in the telephoning condition first. (Note also, this method of controlling for order effects makes it desirable that you run an even number of subjects in your experiment.)

The second problem is choosing an appropriate telephone conversation to use as an interference task. You will explore how the content of the telephone conversation may relate to the degree of interference in a subsequent exercise. For now, to simplify things a little, you will use a sample conversation script.

Method

Each trial will begin with the subject seated comfortably before the blue prompt screen of the driving simulator. A trial consists of a single run through a simulated driving scenario. The subject will begin the simulation, when ready, by pushing the shift lever forward. The subject (the driver) will signal the experimenter when she has started the run.

The driver's task will be to complete the driving scenario as quickly as possible while driving safely and obeying the rules of the road. During the telephone interference trials, the driver must answer the telephone unit when it rings, and attempt to accurately respond to the questions posed by the caller on the other end of the line.

In the course of the experiment, each subject will complete six different driving scenarios in six simulation runs. Three of the runs will be in the telephone interference condition, the remaining three will be in the no-interference condition. Drivers with odd subject numbers will perform the three no-interference runs first and the three telephone interference runs second. Drivers with even subject numbers will perform the three telephone interference runs first and the three no-interference runs second.

In the course of the experiment, each subject will complete six different driving scenarios in six simulation runs. Two of the runs will be Practice, two will be in the telephone interference condition A, the remaining two will be in the telephone interference condition B. Drivers will run the six scenarios in two trial sets (each composed of three trials): a Suburban driving trial set, and an Urban driving trial set. Each trial set will begin with a Practice run. Within each trial set, drivers with odd subject numbers will perform the no-interference condition runs second and the interference condition runs third. Drivers with even subject numbers will perform the interference condition runs second and the no-interference condition runs third.

The summary table below may help you visualize the structure of the experiment.
Practice Condition
(don't collect data)
No Interference Condition
(odd numbers do this first)
Telephone Interference Condition
(even numbers do this first)
Trial Set 1 (Suburban) Suburban 11 Suburban 21 Suburban 31
Trial Set 2 (Urban) Urban 12 Urban 22 Urban 32
During the telephone interference trials the driver will receive a telephone call from the caller. The caller will call the driver 15 to 30 seconds after the beginning of each run. The caller will ask the driver questions specified by a script, record whether the answers are appropriate, and make general comments. The caller will continue to ask scripted questions until the driver has indicated she has reached the end of the simulation run. During the second interference trial, the caller will begin the scripted questions with the first question that was unasked during the first interference trial.

The dependent variable in this experiment is the number of mistakes the driver makes during each trial. The independent variable is the presence or absence of a telephone conversation during driving.

Note: you will want to collect data from at least four subjects in this exercise.

Instructions

Assign the subject a unique number. Start with #101. The subsequent subject numbers should be consecutive, if possible.

NOTE: Please see Equipment instructions above on how to use the driving simulator.

If the subject's number is odd (certainly true for subject #101), his or her first non-practice trial should be in the no-interference condition . If the subject's number is even, his or her first non-practice trial should be in the telephone interference condition.

Suburban trial set

Practice with Suburban scenario 11. Then run Suburban scenario 21. Finally, run Suburban scenario 31.

Urban trial set

Practice with Urban scenario 12. Then run Urban scenario 22. Finally, run Urban scenario 32.

Running subjects in the Interference Condition

You will need at least one other person involved in the telephone conversation runs, besides the subject -- the caller. The caller will be the person on the other end of the telephone. (You, the experimenter, may be too busy supervising the run to function as the caller. However, if you feel comfortable acting as the caller, there is no intrinsic reason why you can't do it.)

Prior to beginning the simulation run, the caller will sit at one of the Mac-compatible computers with a telephone base near it. On the Mac-compatible computer, the caller will:

  1. Open the Driving Module folder.
  2. Open the Telephone Scripts folder.
  3. Open the Microsoft Excel file called "phone script 1".
  4. Read the instructions highlighted in green at the beginning of the script.
  5. Read over the script to become familiar with the questions.
  6. From the File menu choose Save As.
  7. Save the file in your personal folder (on your Zip disk). If you don't have a folder for the Driving Module you can create one now:
    1. Navigate the Save As dialog box to your Zip disk.
    2. Create another folder on your Zip disk called Driving Module.
    3. Open the newly created Driving Module folder.
    4. Change the name of the "phone script 1" file to "ps1.data.YOURNAME".
    5. Save a copy of the script in your folder.
    Note: Put all files you wish to keep on your Zip disk, not on the hard disk, where they are liable to be deleted.
The Excel file includes instructions for the caller. It will be easiest for the callers to wear headsets, in addition to the drivers wearing them. In general, during the run the caller will:
  1. Mark the time the driver begins the run.
  2. Call the subject at a specified (in the Excel file) time after the beginning of each run by:
    1. Picking up the handset
    2. Pushing the Intercom button
  3. Ask the subjects questions specified by the script.
  4. Record the answers, where relevant (the answers that need to be recorded are few and brief; they are marked in RED to make them easy to identify).
  5. Mark whether the subject is answering the questions appropriately.
  6. Make brief comments about any unusual activity (for example, the subject is taking a very long time to answer a question).
  7. When the driver has indicated the run is over, the caller should hang up the phone, marking the last question she asked on the script in preparation for the next run.
OK, you're ready for the telephone conversation (interference) run.

Suburban trial

  1. Get the driver ready to start the correct suburban scenario (See Equipment instructions and the Methods section, above):
  2. Make sure the scenario is ready to run (the driver should be looking at a blue screen that's prompting him to "push the right button")
  3. Make sure the caller will be able to mark the time at which the driver pushes the shift lever forward to begin the run.
  4. Make sure the phone script file is open and ready for use.
  5. Run the scenario.
  6. Save your data.

Urban trial

  1. Now repeat the above five steps with the appropriate Urban scenario (see the Methods section, above).
    You will want to follow the same procedures you did for running the Urban interference scenario, with one exception -- the caller should read the telephone script from the point where she stopped at the end of the last run, not from the beginning. (You don't want to ask the subject the same set of questions twice.)
  2. Save your data.
Congratulations! You just finished running your first subject! Don't forget to transfer the data from the STISIM computer to an Excel workbook on a Mac. (See instructions on Saving Your Data above.)

Questions

Laboratory Exercise Two: Effects of Conversation Content

Reading Assignment Four

Discussion

Goal

In this exercise you will examine how conversation content may influence the extent to which telephoning interferes with driving. We will use the "no interference" data we collected in Exercise One as a baseline to measure the amount of interference.

You will perform this exercise in three steps. First, you will determine what dimension of conversation content you will test. Second, you will produce two script representing the extremes of the conversation content dimension you would like to test. (Feel free to use the scripts you generated during your discussion as a starting point.) Third, you will have the subjects drive while conversing on the telephone in both interference conditions.

Method

Each trial will begin with the subject seated comfortably before the blue prompt screen of the driving simulator. A trial consists of a single run through a simulated driving scenario. The subject will begin the simulation, when ready, by pushing the shift lever forward. The subject (the driver) will signal the experimenter when she has started the run.

The driver's task will be to complete the driving scenario as quickly as possible while driving safely and obeying the rules of the road. During the telephone interference trials, the driver must answer the telephone unit when it rings, and attempt to accurately respond to the questions posed by the caller on the other end of the line.

In the course of the experiment, each subject will complete three different driving scenarios in three simulation runs. One of the runs will be Practice, one will be in the telephone interference condition A, the remaining one will be in the telephone interference condition B.

The trial set will begin with a Practice run. Within the trial set, drivers with odd subject numbers will perform the Conversation Condition A runs second and the Conversation Condition B runs third. Drivers with even subject numbers will perform Conversation Condition B runs second and the Conversation Condition A runs third. To save time, you will use the data you collected in Exercises One and Two to estimate driver performance in the no-interference condition.

The summary table below may help you visualize the structure of the experiment.
Practice Run
(don't collect data)
Telephone Interference Condition A
(odd numbers do this first)
Telephone Interference Condition B
(even numbers do this first)
No-Interference Condition B
(use data from prior experiments)
Trial Set 1: Easy Driving Condition Suburban 11 Suburban 21 Suburban 31 Use no-interference condition data from Exercise One

During each trial the driver will receive a telephone call from the caller. The caller will call the driver 15 to 30 seconds after the beginning of each trial. The caller will ask the driver questions specified by a script, record whether the answers are appropriate, and make general comments. The caller will continue to ask scripted questions until the driver has indicated she has reached the end of the simulation run. During the second interference trial, the caller will begin the scripted questions with the first question that was unasked during the first interference trial.

The dependent variable in this experiment is the number of mistakes the driver makes during each trial. The independent variable is the type of telephone conversation engaged in while driving.

Instructions

1. Find some dimension of conversation content you would like to test You will determine, based on your readings and earlier discussion, what dimension of conversation content you will test. The dimension should be such that you can easily and uncontroversially write two scripts, one clearly scoring high on the dimension of interest, the other clearly scoring low. If you are completely confused, or stuck, take a look at some examples below:
  1. High vs. low cognitive load (e.g., difficult arithmetic problems vs. simple arithmetic problems)
  2. Spatial reasoning vs. nonspatial reasoning (e.g., ask driver to give walking directions from one campus building to another vs. ask driver to give cooking directions)
  3. High emotional content vs. low emotional content (e.g., ask driver to tell you why stealing is wrong vs. ask driver to tell you why abortion [or making abortion illegal] is wrong)
  4. Automatic processing vs. control processing (shadowing task v. paraphrasing task)
The table may help you organize the concepts involved:
Dimension High Low
Cognitive Load Difficult Arithmetic Problems Simple Arithmetic Problems
Spatial Reasoning Give Driving Directions Give Cooking Directions
Emotional Content Justify a Charged Issue Justify a Neutral Issue
Automaticity Shadow Story Paraphrase Story
If you don't have some other dimension of conversation content you would like to explore, feel free to use any of the examples as the basis for your scripts.

2. Type up the scripts On your Mac-compatible computer

  1. Open the Driving Module folder.
  2. Open the Telephone Scripts folder.
  3. Open the Microsoft Excel file called "phone script base".
  4. Read the instructions highlighted in green at the beginning of the script.
  5. From the File menu choose Save As.
  6. Save the file in your Driving Module folder (on your Zip disk) as "psA.data.YOURNAME".
  7. Once more select Save As from the File menu.
  8. Save the file in your Driving Module folder (no need to navigate any subdirectories) as "psB.data.YOURNAME".
You will use "psA.data.YOURNAME" to write the script for Conversation Condition A. You will use "psB.data.YOURNAME" to write the script for Conversation Condition B. NB: If you are working in a group, keep in mind that if you will be using people in your group as subjects your script must be sufficiently variable so that no one can remember the answers to the questions. A driver should never know the precise questions she will be asked, although it's not fatal if the driver knows the general form of the questions she will hear.

There are several ways to do this. One is to write the questions in modular form, with interchangeable elements. Example: [arithmetic problem ] {one digit number} {plus} a {two digit number}; {three digit number} {minus} {a three digit number}. You can then let Excel shuffle the elements around randomly before each trial. Another way is to have a large pool of potential questions. You can use Excel to randomly choose a subset of questions to ask for each trial. (You can use Excel to assign each question a random number prior to each trial, then sort the questions by the random number field.)

However, the simplest way to do this is for each experimenter to produce their own scripts (or a sufficiently large set of questions) so that the remaining members of the group never have to answer questions they are familiar with. 3. Run the driving simulations Finally, you are ready to put your scripts to work. Assign the subject a unique number. Start with #301. The subsequent subject numbers should be consecutive, if possible. NOTE: Please see Equipment instructions above on how to use the driving simulator.

The subject should "warm up" by driving through at least one Urban and one Suburban scenario. Make sure you clearly label the data generated by the warm-up exercises so as not to confuse them with the real data. (I recommend assigning all warm-up exercises the Patient code "000," and typing "Warm Up" in the name field.

Remember, if the subject's number is odd, run the two trials in the Conversation Condition A first. If the subject's number is even, run the two trials in the Conversation Condition B first.

Easy Driving Trial Set

Practice with Suburban Scenario 11. Then run Suburban Scenario 21. Finally, run Suburban Scenario 31.

Conditions

Practice condition

Run "Suburban Scenario 11" and "Suburban Scenario 41" without interference:

Conversation Condition A

Generally, follow the same procedure you did for the interference condition in Exercise One.

Get the driver ready to start the scenario. (See Equipment instructions above).

  1. Make sure the scenario is ready to run (the driver should be looking at a blue screen that's prompting him to "push the right button").
  2. Make sure the caller will be able to mark the time at which the driver pushes the shift lever forward to begin the run.
  3. Make sure the phone script file (psA.data.YOURNAME in the Driving Module folder on your Zip disk) is open and ready for use.
  4. Run the scenario.
  5. Save your data to your Zip disk.

Conversation Condition B

On the Mac-compatible computer, the caller will
  1. Open the Your personal Driving folder.
  2. Open the psB.data.YOURNAME file you created earlier.
  3. Proceed exactly as you did for Conversation Condition A.

General Questions