Introducing "inattentional deafness" – the noisy gorilla that’s missed

One of the most famous experiments in cognitive psychology (pdf) involved a person in a gorilla suit walking through a basketball game between two teams of players, one dressed in white and the other in black. Told to count passes between the players in white, most people who watched a video of this scene completely failed to notice the gorilla. The experiment provided a dramatic demonstration of what's known as inattentional blindness – our failure to process unexpected visual stimuli that we aren't paying attention to. Now a pair of researchers at Royal Holloway, University of London have provided the first demonstration of prolonged inattentional deafness. Their participants failed to hear a man walk through an auditory scene for nineteen seconds saying repeatedly "I am a gorilla".

Polly Dalton and Nick Fraenkel first created a real auditory scene lasting 69 seconds, in which two conversations about a party took place: one between a pair of women located on one side of the room, the other between a pair of men located on the other. The sounds were recorded via a dummy's head with microphones implanted in its "ears", thus simulating as closely as possible what it would be like for a person to actually hear the scene unfold in real life. Thirty-three seconds into the scene, a man entered from the back of the room and for 19 seconds walked through the scene uttering "I am a gorilla" (listen to the recording).

In an initial study, 40 participants listened to the scene and they were told to pay attention either to the men's conversation or the women's. Afterwards, they were asked if they'd heard anything odd. Of the participants who were focused on the men's conversation, 90 per cent noticed the gorilla. In stark contrast, just 30 per cent of participants who were focused on the women's conversation noticed the gorilla.

So, in the same way that tuning out the sight of the basketball players in black led most participants (in the classic research) to miss the sight of an unexpected black gorilla, tuning out the sound of the men's conversation led most participants in this study to completely miss the sound of a male-voiced gorilla.

A potential confound in this new study is that as the auditory gorilla passed through the room, he walked behind the location where the two men were talking. This means that participants focused on the women could have been ignoring male voices and/or one particular side of space. In a second study, the location of the auditory gorilla was reversed so that he passed behind the women. This time 55 per cent of participants focused on the women's conversation still failed to notice the gorilla even though he actually passed on the same side of space that they were focused on.

"The present experiments show that the absence of attention can leave people 'deaf' to a sustained and dynamic auditory stimulus that is clearly noticeable under normal listening conditions," the researchers said, "providing the first-ever demonstration of sustained inattentional deafness."

Further reading

Dalton P, & Fraenkel N (2012). Gorillas we have missed: Sustained inattentional deafness for dynamic events. Cognition PMID: 22726569