Why do we sometimes not register sounds and voices around us? A wife asks her husband for the third time, "did you take the garbage out yet?" He is so glued to the big game and he still hasn’t issued a response. A kid doesn’t hear her mother tell her dinner is ready because she is fully immersed in her favorite video game. You miss part of the conversation you were having with your friends at a coffee shop because you were too busy checking for new email, comments and tweets on your smart phone for the millionth time today (that one I can relate to). What do these three scenarios have in common? Our bodies trying to balance our sensory perceptual load between vision and hearing and one of these senses ultimately falls short.

Researchers in the United Kingdom have demonstrated for the first time a phenomenon known as inattentional deafness. It seems when we are concentrated on a highly involved visual task, we block out auditory information around us that is unrelated to the task at hand. In other words, we may be involuntarily putting sounds “on mute” while we concentrate on activities that take a great deal of our attention visually and and this can turn us into poor listeners.

Inattentional Blindness:

Now we have all probably heard of something called "inattentional blindness" and the infamous visual awareness test that Chabris and Simons conducted back in 1999 in which one is asked to watch a video and count the number of times a basketball is passed by one of two teams. If you haven’t seen it, it was similar to the following video. Check it out!

Visual Awareness Test (by dothetest.co.uk):

In the original version of this test, also known as the “invisible gorilla” experiment by Chabris and Simons, the mental task of counting passes had about 50% of viewers so distracted that they were visually unaware of the gorilla walking (or in this case, the bear moonwalking) right into the middle of the screen. A moonwalking bear, hello? A gorilla beating on his chest? Come on! (For the record, I missed both!)

Perhaps you have also heard about the study that came out in 2009 in which distracted cell phone users were visually unaware of a clown on a unicycle passing them as they were walking and chatting away on their phone. I mean, really. How could you not notice a clown pedaling right passed you on a unicycle!

Visual awareness has been well researched and there are many interesting studies out there on how distractions can take away from your vision. If you’d like to have a little more fun with it, I will list a couple of other videos at the end of this post. But for now let’s turn our attention towards hearing and distractions causing a decrease in our auditory awareness. What is this newly named phenomenon of inattentional deafness?

Inattentional Deafness:

In May 2011, Macdonald and Lavie set up a series of experiments putting the theory of inattentional deafness to the test. They found subjects were able to hear a beeping sound being played through headphones while they performed a visual task on the computer if the task was relatively easy but as the level of difficulty of the visual task increased, they became unaware that a sound was even there.

The setup of the experiment went like this. On the computer screen, a series of crosses were presented to participants, one by one, each for a short interval. The cross had one green arm and one blue arm and the lengths of the arms on the cross varied slightly. Each person was asked to either indicate which arm was blue or judge which arm was longer. Determining color was thought to be a very easy visual task with a low amount of perceptual load. Conversely, participants who were asked to detect the subtle difference in length of the two arms were said to have a more challenging task, requiring more visual attention and therefore having to endure a higher perceptual load.

The experiment had three parts. In the first part, experiment 1, white noise was played through the headphones and participants were told that they were to wear the headphones throughout the experiment. Researchers said the white noise would “aid concentration by blocking out noise from people passing the testing room...[according to researchers] participants seemed to take this instruction at face value and did not seem suspicious [of the need to] block out the sound of people passing by.”

During the last cross presentation, the white noise was accompanied by a beeping sound. Participants were then stopped and asked at the end if they had heard “anything different about the sound coming through the headphones during the last trial?” Their response was noted. Then they were asked to perform one more trial in which they were told to ignore the cross and just listen to the sound coming through the headphones to make sure each person had good enough hearing to detect the sound. If they didn’t hear it when they were actively listening for it, then they were excluded from the study and replaced.

From the results in Experiment 1, Macdonald and Lavie concluded that their hypothesis was in fact correct. At times when a higher visual load was presented (determining length of the arms of the cross), the participants were less likely to hear the task-unrelated tone sounding through their headphones.

However, they wanted to prove their point further so they did a second experiment without the white noise. They thought that maybe the presence of white noise could possibly cause subjects to actively ignore all noise during the entire experiment. By taking away the white noise from the headphones, the presence of sound (versus natural silence) should be easier to detect and therefore be more noticeable. They found that, again, when the participants had the more dauntingly visual task of detecting the subtle difference in the length of the arms on the cross, they were a lot less likely to notice the beeping sound being played through the headphones, even in the absence of all other sound. So again, if a task takes a lot of visual concentration and attention, it can cause a decrease in auditory awareness. Now you think they would stop there, but Macdonald and Lavie took it to the next level once more.

In experiment 3, they sought to eliminate the possibility that those who were on the low perceptual load team were a little aloof during the experiment and those who were on the high perceptual load team maybe were a little more motivated, engaged and attentive because of the nature of their work being a little harder. So they made it a length only discrimination task where each person was asked nothing about color, only which arm of the cross was longer. Sometimes the difference in lengths between the arms of the cross was grossly obvious, other times it was subtle. They also increased the number of trials presented. Macdonald and Lavie found that still, those with a higher perceptual load (distracted with determining a more subtle difference in arm length) heard the sound less often than those who had the easier visual task of the more grossly obvious difference in cross arm length. Their results were “not as robust” but they were still there.

More studies need to be conducted on inattentional deafness to truly see how it affects our everyday lives. Macdonald and Lavie have concerns about inattentional deafness and driving a motor vehicle stating that if people were “less likely to notice an auditory alarm while engaged in a high-visual-load computer task, [then] the sound of a car horn while attending to a visually loaded billboard” also might pose a problem. Safety out on the roadways is definitely a concern.

Perhaps another interesting modification to the study would be to replace the tone sounding through the headphones with a person’s voice saying a word. Maybe a bizarre word that you wouldn’t just happen to overhear in the laboratory like zebra or halloween. Would the participant be completely unaware of human speech like it was of the tone when engaged in a highly visual task?

After researching this topic, I know I will be practicing more patience when I catch someone not listening to me. It may not have been intentional. And also I pledge to put down the smartphone and have some real “face-time” with the person sitting right across the table from me the next time I’m out for coffee. After all, they are deserving of my undivided attention. My emails, texts and tweets can wait. Unless of course I see a moon-walking bear, then all bets are off, sorry guys, I have to tweet pic that.

Additional tests of your visual awareness:

The Colour Changing Card Trick (by Richard Wiseman/Quirkology):

Test Your Awareness: Whodunnit? (by dothetest.co.uk ):

Also, check out the fun book by Chabris and Simons, The Invisible Gorilla: How our Intuitions deceive us.

Photo Credits: Man with glasses (Matt Jeacock /istockphoto), i-distractions and Author pic (Erica Angiolillo/Gotcha! by Erica), Bear (Trine de Florie /stockxchg photo).


Boss, M. Caggiano, J. Hyman, I. McKenzie, K. Wise, B. (2010) Do You See the Unicycling Clown? Inattentional Blindness While Walking and Talking on a Cell Phone. Applied Cognitive Psychology. 24:597-607.

Chabris C. and Simons, D. (2011) The Invisible Gorilla: How our Intuitions deceive us. New York: Crown Publishing Group.

Macdonald JS and Lavie N. Visual perceptual load induces inattentional deafness. Atten Percept Psychophys. 2011 Aug; 73(6):1780-9. doi: 10.3758/s13414-011-0144-4