This is a test of your attentiveness.
Watch this video (seriously, watch the video before reading anything below):
So, did you guess the number of passes correctly? No matter. More importantly, did you see the gorilla?
A similar vein of research like that of the "invisible gorilla" experiment conducted at Harvard University in 1999 that exhibits "selective attention" with regard to sight was also found to hold true for hearing.
When your spouse, significant other, sibling or best friend is watching TV, how hard is it to get his or her attention? Do you have to say his or her name five times getting louder each time before he or she reluctantly turns his or her head toward you? This is selective hearing.
The researchers from Royal Holloway-University of London conducted a "silent gorilla" study where they asked participants to listen to two different conversations. Try it out for yourself on the researchers' website here.
You may or may not have noticed it, but a voice in the video says "I'm a gorilla" repeatedly.
“We’re much less aware of the world around us than we tend to think” Dr. Polly Dalton with the university's psychology department said in a statement. “This research demonstrates that we can miss even very surprising and distinctive sounds when we are paying attention to something else.”
Well, Did you hear it? Depending on whose conversation you were really focusing on, you may have been swayed to tune out the oddly out of place phrase. According to the university website, those who were listening to the two men talking were more likely to hear "I'm a gorilla," compared to those who were listening to the two women.
The male voice saying "I'm a gorilla" goes on for about 19 seconds starting around 1:12 in the audio.
“We were surprised to find such extreme effects with a listening task, because people often think of hearing as an ‘early warning system’ that can alert us to unexpected events that occur out of sight. The fact that a lack of attention can cause people to miss even distinctive and long-lasting sounds questions this view. This has real-world implications in suggesting, for example, that talking on your mobile phone is likely to reduce your awareness of traffic noises.”
(H/T: Huffington Post)