Participants had to smell chlorine, gunpowder or a flower. Photo: Aleksandrs Tihonovs Mostphotos
Participants had to smell chlorine, gunpowder or a flower. Photo: Aleksandrs Tihonovs/Mostphotos


“In our previous research, we have shown that memory cues in the form of, for example, words, images and sounds elicit a large proportion of memories that occurred when participants were young, between 15–30 years. But if odors  are used as clues, this so-called memory bump is shifted to early childhood, that is between 0–10 years”, says Stina Cornell Kärnekull, a researcher at the Department of Psychology, Stockholm University, and first author of the study published in the scientific journal Consciousness and Cognition.
 

Stina Cornell Kärnekull, researcher at the Department of Psychology. Photo: Hans Bergman
Stina Cornell Kärnekull, researcher at the Department of Psychology. Photo: Hans Bergman

In 2018, she published her thesis on differences between the cognitive and perceptual odor and hearing abilities of blind and sighted persons. In the new study, she and a group of researchers at Gösta Ekman’s laboratory investigated whether memory cues, for example, odors and sounds, could result in the same type of memory in the blind as in sighted persons. The study is conducted within the framework of the research program “Our unique sense of smell” funded by Riksbankens Jubileumsfond.
 
“We wanted to know if the fact that one does not have access to visual information changes how memories are encoded and retrieved.”

Odors and sound cues

In the study, the researchers have data where they have presented odor and sound cues to people who are early blind, which means from birth or early childhood, and compared their memory retrieval with sighted people. The researchers found that when early blind people get odors as memory cues, they get, just like sighted, the highest proportion of memories from early childhood. If, on the other hand, they get to listen to different environmental sounds, they get most of the memories from the age of 11–20, just like sighted people.
 
“This says something fundamental about how memories are encoded and retrieved. A sighted person can, unlike an early blind person, associate visual impressions with odors and sounds, for example by imagining a lawnmower when you feel the smell of grass or hear the sound of it. Nevertheless, we found that memory retrieval did not differ between groups.”
 
“This is remarkable because it means that what controls these processes has nothing to do with how different senses interact with each other. Many studies have shown that blind people can compensate for their loss of vision or impairment by developing other abilities, such as attention to sound, but it does not appear to affect these memory processes.”
 
How memory cues in different sensory modalities evoke memories from different parts of life has been studied by many research groups in the world, but none of these studies have examined blind people, according to Stina Cornell Kärnekull.
“This is problematic because we know that vision is important for memory encoding, that is, how memories are built up.”

Participants had to smell chlorine, gunpowder or a flower

In the present study, 31 early blind and 31 sighted persons participated, which is a fairly large number compared to other similar studies. Some of the participants had to smell for example chlorine, gunpowder, pine needle and a flower, while other participants listened to the corresponding sounds of a bathhouse, fireworks, a forest walk and the sound of a summer day with buzzing bees.
“Our study shows why it is important to include people with other experiences in research. In this way we can achieve knowledge that we would never have been able to do if we had only studied sighted people.”

More information

The article “The reminiscence bump is blind to blindness: Evidence from sound-and odor-evoked autobiographical memory” is published in the scientific journal Consciousness and Cognition.