Inattentional blindness is a well-studied phenomenon in psychological research. This dynamic plays out when, absent any vision problems, individuals are so focused on a visual aspect of a scene that they fail to notice some other, highly visible feature. The Invisible Gorilla experiment is among the most famous illustrations of this effect. A video shows three people in white shirts and three people in black holding basketballs. Text on the video screen challenges the viewer to count the number of passes the team in white makes throughout the video. In an experiment by APS Fellow Daniel J. Simons of the University of Illinois at Urbana-Champaign and Christopher Chabris of Geisinger Health System, most viewers could count the number of passes accurately, but about half of them missed the person dressed in a full gorilla costume walking through the middle of the basketball passers as they dribbled.
Inattentional blindness has implications for driving, aviation, and witness testimony. Psychological scientists Sophie Forster at the University of Sussex and Charles Spence at the University of Oxford wondered if attention also could cause people to “miss” smells in a similar fashion. Their research appears in Psychological Science.
Forster and Spence set up a room to be distinctively aromatic, hiding three small containers of coffee beans around the room overnight. Across the course of two experiments, they led 40 college students into the room one at a time to perform a tough visual-search task on a computer, searching for the letter “X” or “N” in a circle of similar-looking letters (“W,” “M,” “K,” “H,” “Z,” and “V”). Forty other students completed an easier version of the same task, looking for the letter “X” or “N” among a circle of lowercase “o”s.
The experimenters then took the students into another room and asked them some follow-up questions that grew increasingly leading:
- “Describe the room you just completed the task in. Try to describe it using all of your senses.”
- “Did you notice any odors in the room? If so, what?”
- “Could you smell coffee in the room?”
Students assigned to the difficult search task were far less likely to report having picked up the aroma (25% of participants) compared with participants assigned to the easy task (60–70% percent of participants). When the experimenters led the students back into the test room, all of them said they could smell the coffee. Some of them even commented that the room smelled like a cafe.
After two experiments testing the basic hypothesis, the researchers decided to see how long these smell-blocking effects might last. They had 20 students focus on the difficult visual-search task in a room that smelled strongly of coffee. Then, while still in that room, the students were asked to describe the test room and its smells. Even though they were sitting in a room with 3 open containers of coffee beans, only 30% of participants said they smelled coffee. This experiment suggested that the effects of selective attention last after even after the attention-absorbing task is over. When they left the room for a few minutes and came back, all of them could smell the aroma.
The report authors suggest that this phenomenon has advantages. Individuals could, for example, resist junk food if they’re too engaged with a task to even smell it. But this temporary loss of smell also can pose dangers, leaving a person oblivious to a fire or gas leak if she misses the threatening odors such as smoke or gas, according to their report. Some research into inattentional blindness has shown that people do notice dangerous visual cues when their attention is otherwise occupied, but the results have been inconclusive. Forster and Spence advocate for future research to see whether people fail to notice unpleasant or threatening smells when they are focused on another task.
Forster, S., & Spence, C. (2018). “What smell?” Temporarily loading visual attention induces a prolonged loss of olfactory awareness. Psychological Science. doi:10.1177/2F0956797618781325