When it comes to memory, we don't remember things we hear nearly as well as things we see or touch, scientists say.
Researchers at the University of Iowa found our memory for sounds is significantly worse than our memory for visual or tactile things.
"We tend to think that the parts of our brain wired for memory are integrated. But our findings indicate our brain may use separate pathways to process information," said lead author of the study and UI graduate student, James Bigelow.
"Even more, our study suggests the brain may process auditory information differently than visual and tactile information, and alternative strategies - such as increased mental repetition - may be needed when trying to improve memory," said Amy Poremba, corresponding author on the study.
Bigelow and Poremba discovered that when more than 100 UI undergraduate students were exposed to a variety of sounds, visuals and things that could be felt, the students were least apt to remember the sounds they had heard.
In an experiment testing short term-memory, participants were asked to listen to pure tones they heard through headphones, look at various shades of red squares, and feel low-intensity vibrations by gripping an aluminum bar.
Each set of tones, squares and vibrations was separated by time delays ranging from one to 32 seconds.
Although students' memory declined across the board when time delays grew longer, the decline was much greater for sounds, and began as early as four to eight seconds after being exposed to them.
It seems like a short time span, but it's akin to forgetting a phone number that wasn't written down, said Poremba.
Bigelow and Poremba also tested participants' memory using things they might encounter on an everyday basis.
Students listened to audio recordings of dogs barking, watched silent videos of a basketball game, and, touched and held common objects blocked from view, such as a coffee mug.
Researchers found that between an hour and a week later, students were worse at remembering the sounds they had heard, but their memory for visual scenes and tactile objects was about the same.
Both experiments suggest that the way your mind processes and stores sound may be different from the way it process and stores other types of memories.
The finding is important, said researchers, because experiments with non-human primates such as monkeys and chimpanzees have shown that they similarly excel at visual and tactile memory tasks, but struggle with auditory tasks.
Based on these observations, they believe humans' weakness for remembering sounds likely has its roots in the evolution of the primate brain.
The study is published in the journal PLoS One.
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