Cognitive Daily

It has been known for some time that cell phones can lead to driving accidents. After watching the behavior of some other drivers on the road, I’m sometimes surprised that there aren’t more cell-phone-related accidents than there already are. With well over 100 million cell phone users in the U.S. alone, the problem isn’t going to get any smaller.

Until recently, there has been some dispute about exactly why cell phones are unsafe for drivers. Two high-profile studies in the 1990s suggested that any manual manipulation of devices in a car, including not only dialing a cell phone, but also adjusting the radio and other gadgets, led to poor driving. This has led to the rise of hands-free phones, voice-activated phones, and been accompanied by even more gadgets, including GPS, DVD players, and even video games in cars.

In 2001, however, David Strayer and William Johnson of The University of Utah conducted a study which helped narrow down precisely where the danger in cell phone use lies (“Driven to Distraction: Dual-Task Studies of Simulated Driving and Conversing on a Cellular Telephone,” Psychological Science, 2001).

In their first experiment, Strayer and Johnson had volunteers perform a simple simulated driving task: using a joystick to make a cursor to follow a dot moving randomly back and forth across the screen (though this reminds me of the primitive “games” I used to type into my Commodore-64 from computer magazines in the early 1980s, it’s a reasonable simulation of the cognitive demands of driving a car). At random intervals, the dot would turn either green or red. On a “red light,” participants were supposed to press the “brake” button on the joystick. After a practice round with no distractions, participants either had a conversation on a handheld or hands-free cell phone (what did they talk about? The issues of the day while the experiment was being conducted: the Clinton impeachment scandal or the Salt Lake City Olympics bribery scandal). A control group listened to the radio or an audiobook.

Strayer and Johnson found no difference between people who used a handheld or hands-free cell phone, and no difference between radio/audiobook listeners and the driving-only condition. However, the cell-phone talkers missed more than twice as many red lights as the other participants:


In addition to the accuracy problems, cell phone users also showed slower reaction times compared to when they were driving alone.

But does any conversation lead to driving errors? In a second experiment, Strayer and Johnson used a similar apparatus, but instead of using red and green lights, they had participants drive over “easy” and “difficult” courses. The volunteers were first asked to simply repeat words to the experimenter over the telephone. Next they were asked to generate a new word starting with the last letter of the word the experimenter gave them (for example if the experimenter said “salmon,” the volunteer could respond “nicotine”). The results were as follows:


Strayer and Johnson used a statistical method to measure the number of errors the drivers made. There wasn’t a significant difference in errors on the easy course, but on the difficult course, when drivers had to generate words in response, they made significantly more errors. So the key seems to be not simply that drivers are having a conversation, but that they are actively generating responses. In these conditions, drivers are more likely to make errors. If word of this result gets out to the gadget-makers, perhaps the next must-have phone will have a conversation analyzer that automatically warns you if you’re talking safely!


  1. #1 Sunil Bajpai
    June 16, 2005

    Thanks for and interesting post.
    But why is talking on the cellphone more dangerous than talking with a fellow passenger?
    Could it be that fellow passengers change the pace of conversation when the driver needs to concentrate on the driving? For example, they may wait a few seconds longer for his response as he parks in to a tight space.
    Also, I read somewhere that if the speaker is positioned near the windscreen and facing the driver, the phone conversation seems to distract him less.

  2. #2 Dave Munger
    June 16, 2005

    I’ll be reporting on some other cell phone studies in the coming weeks covering some of the questions you’ve asked, Sunil—those are excellent questions. I believe the short answer is that passengers are also distracting.

    Do you remember where you saw that study about the speaker position? I’d be very interested to see that one.

  3. #3 Donna
    June 16, 2005

    Anyone who has had kids knows how distracting passengers can be! Passengers can also be helpful if they are old enough and good drivers themselves, warning about possible dangers.

    The problem with cellphone calls is that person you are talking to isn’t in the car and can’t help you see what’s going on, and can’t shut up and wait when things get difficult. I have the same problem when I’m online or working and interrupted by phone calls, as I think anyone who has been interrupted from a task by a call can atest.

  4. #4 John
    June 18, 2005

    I have always thought that we have not train ourselves to drive and talk on a cell phone. (I am wondering if there is now a decrease in cell phone related accidents?)
    Like what Sunil suggests, we need to learn how to make our conversation secondary to out driving task. I think we have learned that over the years. When cell phones came out, I trained my children how to talk on them. Just like I did with the music and passenger issues. I told them to always annouce that you are driving and to be aware that you may be responding accordingly. And of course if the subject matter is critical… pull over to the side.

    It may be just all a matter of learning. Hey, just what a cognitive pychologist wants to hear:)

  5. #5 Sunil Bajpai
    June 19, 2005

    The report about speaker’s position on level of driver’s distraction, while using hands free cell phones, appeared in the Times of India some time ago.

    They have a website: where I tried to search for it, but wasn’t successful.

  6. #6 Greta
    June 22, 2005

    The newspaper report might have been based on this…

    Spence, C. & Read, L. (2003) Speech shadowing while driving: On the difficulty of splitting attention between eye and ear. Psychological Science, 14(3), 251-156.

  7. #7 dan
    December 20, 2005

    im not a big fan of your web site. im doing a science project and I need actual numbers, and you’re not givin them to me. so please, get rid of this site so students like me dont get their hopes up ever again

  8. […] Although there is a growing consensus that talking on cell phones ¡ª even hands-free phones ¡ª is a distraction that impairs driving ability (we’ve reported on one study by David Strayer and William Johnson confirming this notion), many researchers have suggested that in-person conversation may not have the same effect, because passengers can see the traffic patterns and slow the conversation when a difficult driving situation arises. A group led by Leo Gugerty designed two experiments to try to determine if car passengers adapted their conversation for tough driving situations. Gugerty’s team used a simple driving simulator for their task (you can see it here ¡ª it’s more sophisticated than what Strayer and Johnson used, but still not exactly a realistic reproduction of real driving). In their first experiment, the team used the same task as Strayer and Johnson: the ¡°passenger¡± gives the driver a word, then the driver must repeat a new word that begins with the last letter of the original word. But instead of simply navigating a path, drivers had to perform several tasks designed to replicate real driving, like remembering the locations of other vehicles, avoiding crashes, detecting hazards, or remembering when vehicles were in the car’s blind spot. In a second version of the task, designed to approximate talking on a hands-free phone, the conversants were placed in adjacent cubicles where they could not see the driving similator. Drivers were also tested with no conversation. To motivate them to try their best, driver-passenger teams were told that the best two teams would receive a $25 reward. […]

  9. #9 Torbjörn Larsson
    April 26, 2007

    There wasn’t a significant difference in errors on the easy course, but on the difficult course, when drivers had to generate words in response, they made significantly more errors.

    Ahh, yes! I have always wondered why I can drive and make a fair conversation, but when it also involves planning or checking the route I get swamped. Since I can usually converse, read a book and watch television at the same time (not too intensive conversation from my side of course:-), I was curious why task switching was so difficult here. It seems the genuinely creative parts messes it up.

  10. #10 KeithB
    April 27, 2007

    My take on this is that the brain requires more processing power (concentration) to listen on *any* phone. It hink the combination of lack of body clues and restricted frequency response make it more difficult to hear and understand.

    An analogous situation is the classic Mom line “Keep it quiet! I am talking on the phone!” If that person was int the same room sitting across the table from Mom, she could follow the conversation with no problem, even in the presence of distraction.

  11. #11 Ed Yong
    March 7, 2009

    I think KeithB’s onto something. I remember reading a study which suggested that the inconsistent signal strength of a phone conversation plays a part. Just takes more cognitive effort to decipher a signal of constantly changing strength than it does a more consistent passenger.

    Also, I would suggest that commenter #7 not getting his hopes up ever again would be a suitable life plan.

  12. #12 Loretta Fuller
    December 14, 2009

    To whom it may concern. I would like your permission to use a image from your URL for my college essay. Thank you for listening and please reply.

    Loretta Fuller

  13. #13 Dave Munger
    December 15, 2009


    Unless you are publishing your college essay (for example, on an online website, facebook page, or blog), you don’t need to request permission to use images. They qualify as “fair use” under the “educational use” provision of copyright law.

    If you would like to publish the image in addition to turning it in for class credit, please contact me at Specify which image you want to use and how you are planning on publishing it.

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