Teenagers who smoke, or whose mother used to smoke while bearing the child, are at a very high risk of hearing problems and understanding what is being said, says a study.
The study, led by Leslie Jacobsen at Yale University, reviewed 67 teenagers and found that those exposed to smoke had trouble focusing and interpreting sounds when there was a distraction.
The researchers carried out brain scans on the teenagers, and analysis showed that those exposed to smoke were more likely to have more white matter.
Scans showed exposure changed the brain's white matter responsible for transmitting messages, said the scientists.
The researchers contemplated that the over-production of the white matter was caused by nicotine stimulating a chemical compound called acetylcholine.
Computer tests were given by the teenagers, aged 13 to 18, where they were asked to recognise words while being distracted by visual images or background noise.
The analysis showed that those exposed to smoke got 77 percent right, whereas those not exposed got 85 percent right.
In girls, the breakdown was 84 percent to 90 percent.
"Individuals affected will have problems in settings where there is a distraction. This could certainly be the case in classrooms where there may be other people talking and lots of things going on," BBC quoted Jacobsen, as telling New Scientist.
"Coupled with other conditions, such as behavioural disorders, this may tip a pupil towards failing at school," Jacobsen added.
David McAlpine, director of the Ear Institute at University College London said: "The fact that smokers show changes in this pathway means they may be less able to hear what's being said."
The study is published in New Scientist magazine.