Ira Hyman and colleagues at Western Washington University think a key reason for the adverse cognitive effects of talking on a mobile phone has to do with 'inattentional blindness' - the failure to notice new information in the environment. To circumvent the limitations of the car studies, they've performed a stripped-down, naturalistic study of people walking diagonally 375 feet across their university's Red Square. They noted whether people walking this popular route were talking on a mobile, listening to an iPod, talking with another person who was present, or just walking on their own without any distractions. When these individuals reached the other side of the square, the researchers asked them if they'd noticed the unicycling clown positioned strategically just to the side of the diagonal path. Their report dryly notes the rationale:
'Unicyclists are very rare on campus pathways and none of the authors have ever observed a unicycling clown on campus. Since the clown was unicycling near the walking path, this was clearly relevant to the task of safely navigating across Red Square (besides, you never know when a clown may throw a cream pie in your face).'The take-home message was that of the 151 people who were monitored, the 24 who'd been chatting on a mobile were significantly less likely than the others to have noticed the unicycling clown - 25 per cent of phone users noticed him, compared with 51 per cent of people walking on their own, 61 per cent of music listeners and 71 per cent of people walking in pairs. The result provides further evidence that talking on a mobile phone induces inattentional blindness in a way that listening to music or talking to a person who is present does not (in fact, the company of another person who is present increased vigilance, an effect also found in driving simulator studies).
In an earlier part of this study, Hyman and her colleagues found that people crossing the Red Square while chatting on a phone tended to walk more slowly, to weave and to change directions more than other walkers, perhaps because of the effects of increased inattentional blindness.
Although talking on mobile phones while driving has been banned in many countries, many people continue to believe that they are unaffected by using their phone. This could be because by definition we're not aware of what we've missed. '...[I]ndividuals in our study who did not report seeing the unicycling clown were generally surprised that they missed him,' the researchers said. 'Unfortunately, when driving a car while talking on a cell phone, people may be unaware of what they are missing until it is too late.'
Hyman, I., Boss, S., Wise, B., McKenzie, K., & Caggiano, J. (2009). Did you see the unicycling clown? Inattentional blindness while walking and talking on a cell phone. Applied Cognitive Psychology, 24 (5), 597-607 DOI: 10.1002/acp.1638