I spend most mornings before visiting with clients at St. Elmo’s (my local coffee shop). Besides reading the paper and discussing politics with friends (and, of course, the coffee), what I like most about St. Elmo’s is its firm NO CELLPHONE POLICY. I am sure you, too, feel that overheard cell phone conversations are very distracting. Well, Lauren Embersen, while she was an undergraduate at the University of British Columbia, thought so, too. The difference is that she performed the research to find out why (for her Ph.D. at Cornell University). The study results (co-authors are Michael Goldstein [Cornell University], Michael Spivey [University of California at Merced] and Gary Lupyan [University of Wisconsin-Madison]) are published in Psychological Science (September 2010; one needs to be a subscriber to read the document). It turns out hearing half a conversation is much more distracting than hearing the entire discourse.
Ms. Embersen recording two pairs of female roommates holding a cell conversation- as a dialogue (both sides heard) and a “halfalogue” (only one side of the conversation could be
heard, i.e., a simulated overheard cell phone conversation). A monologue version (one person recapping the conversation) was also recorded.
These recordings were then played for 24 volunteers at modulating volumes (and silence,
as the control), who performed two different tasks on a computer. One test involved tracking a moving dot on the monitor with the
mouse. The other test required them to push a button whenever they saw four specific letters flash on the monitor. The volunteers were requested to ignore the sounds and just concentrate on the assignment.
Performance (missed responses, incorrect hits) was the worst when the “halfalogue” was heard. Overhearing the dialogue provided a six-fold response for the moving dot test when compared to the “halfalogue”. The letter response test performance dropped 10% during the “halfalogue” (when compared to the dialogue, silence, or monologues). The “halfalogues” were also adjusted to sound muffled (as if underwater) to test if the acoustic characteristics of the voice affected performance (and not the unpredictability); there was no significant effect.
Ms. Embersen postulates that our brains tend to ignore predictable items, but pays closer attention to those items that are not predictable. A dialogue flows predictably, so we tend to ignore it. However, overheard cell conversations, with varying bursts of noise and silence, are much less predictable to our brains.