The Cocktail Party Effect

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For psychologists the ‘cocktail party effect’ is our impressive and under-appreciated ability to tune our attention to just one voice from a multitude. At a party when bored with our current conversational partner — and for the compulsive eavesdropper — allowing the aural attention to wander around the room is a handy trick.

Perhaps only the most recidivist eavesdroppers are aware how special this ability is. But even they might be surprised — and worried — by just how much we can miss in the voices we decide to tune out.

Close your eyes and concentrate

Our ability to separate one conversation from another is beautifully demonstrated in a classic study carried out by Colin Cherry, then at Imperial College London (Cherry, 1953). Cherry used the simple method of playing back two different messages at the same time to people, under a variety of conditions. In doing so he discovered just how good we are at filtering what we hear.

In the first set of experiments he played back two different messages voiced by the same person through both ears of a pair of headphones and asked participants to ‘shadow’ one of the two messages they were hearing by speaking it out loud, and later by writing it down.

To accomplish this task, Cherry reports, participants had to close their eyes and concentrate hard. When doing this they could, with effort, and while hearing the clips over and over again, separate one of the messages from the other.

With the two voice presented together, as though the same person were standing in front of you saying two completely different things at the same time, this task appears to be very hard, but still possible. Pushing participants further Cherry found he could confuse listeners, but only by having both messages consist entirely of nonsensical platitudes. Only then were participants unable to pick apart one message from the other.

Receiving you loud and clear

The real surprise, though, came in the second set of experiments. For these Cherry fed one message to the left ear and one to the right ear — and once again both messages were voiced by the same speaker.

Suddenly participants found the task incredibly easy. Indeed many were surprised how easily and accurately they could tune in to either one of the messages, and even shift their attention back and forth between the two. No longer did they have to close their eyes and furrow their brows – this was much easier.

What participants were experiencing here seems much closer to most people’s experience of picking out one conversation from a multitude. At a party people are arrayed all around us and their conversations come from various different directions. We seem to be able to use this information to reject all but the one in which we are interested.

I’m sorry, what were you saying?

Although we are fantastically good at tuning in to one conversation over all the others, we seem to absorb very little information from the conversations we reject. That’s where it can get embarrassing.

Cherry found his participants picked up surprisingly little information presented to the other, ‘rejected ear’, often failing to notice blatant changes to the unattended message. When asked afterwards, participants:

could not identify a single phrase from the speech presented to the rejected ear.

weren’t sure the language in the rejected ear was even English.

failed to notice when it changed to German.

mostly didn’t notice when the speech to the rejected ear was being played backwards (though some did report that it sounded a bit strange).

Across all the different conditions tried there were only two aspects of the speech to the rejected ear the participants could reliably identify. The first was that it was speech compared to a tone, the second was when the speaker suddenly changed from male to female.

This doesn’t bode at all well for people with a habit of tuning out of conversations when they lose interest (you know who you are!). If you really are listening to someone else it’s likely you won’t hear a word of what’s being said to you directly. One study has found that two-thirds of people don’t even notice when their own name is slipped into the unattended speech, while those who do notice are likely to be of the extremely distractable variety (Conway, Cowan & Bunting, 2001).

You have been warned!

[Image credit: andruby & yasu2909]