Report: Overheard cellphone conversations are incomplete, unpredictable distractions

Listening to one side of a conversation can be unsettling.
Listening to one side of a conversation can be unsettling. (Rubberball/alamy)
Monday, October 4, 2010; 5:54 PM

Hearing half a dialogue can be more distracting than hearing both sides

Have you noticed, while sitting on the Metro or waiting in an office, that it's hard to ignore a cellphone conversation going on near you? You're hearing only half the conversation, but, according to a group of researchers, that's precisely why it may be hard for you to concentrate on your own tasks.

Unpredictable noises - or silences - tend to distract, and the one-sided conversations of overheard cellphone chats - what the researchers termed "halfalogues" - fall well into that category.

To test the effect, researchers from Cornell University selected 24 undergraduates and gave them two tasks.

First, they were told to use a computer mouse to track a moving dot on a computer screen; then they were instructed to push a button every time they saw four specific letters flash on the screen.

They completed these attention-requiring tasks while the researchers randomly played a recording of a two-person dialogue, a one-person monologue or a halfalogue. Researchers controlled the volume and told the participants to ignore the sounds and just concentrate on the assignment. At other times, no recording was played and the tasks were done in silence.

The researchers found that performance was lowest - as determined by missed responses, incorrect hits and other mistakes - when the halfalogues were being played.

In the moving-dot test, the students reacted six times faster during the dialogue than during the halfalogue.

On average, students did 10 percent worse on the letter-response test when they heard the halfalogue than when they worked in silence or when they heard dialogues or monologues.

To ensure that these differences were caused by the halfalogue's unpredictable and incomplete nature - and not the acoustic characteristics of speech - researchers filtered the one-sided conversation so that it sounded muffled, as if the voice were being heard underwater. That had no significant effect on participants' accuracy. "This leads us to believe it has to do with the information content being unpredictable," said Lauren Emberson, lead author of the study. The results were published in the September issue of Psychological Science.

- Leslie Tamura

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