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In the brain, nicotine binds to specific molecules on nerve cells called nicotinic acetylcholine receptors, or nAChRs. When nerve cells communicate, nerve impulses jump chemically across gaps between cells called synapses by means of neurotransmitters. The neurotransmitters then bind to the receptor sites on nerve cells — in the case acetylcholine resulting in the release of a pleasure-inducing chemical called dopamine. Nicotine mimics acetylcholine, but it lasts longer, releasing more dopamine.

"It can cause specific neurons to communicate and thus increases dopamine for an extended period of time," Brody said. "Most scientists believe that's one key reason why nicotine is so addictive."

Psychologists at the University of Virginia and the University of Plymouth (United Kingdom) have conducted experimental research that contrasts with the belief that happy children are the best learners. The findings, which currently appear online in the journal Developmental Science ( www.blackwell-synergy.com/doi/full/10.1111/j.1467-7687.2008.00709.x ), and will be printed in the June issue, show that where attention to detail is required, happy children may be at a disadvantage.

Children who have been separated at any point scored significantly worse both on the 4-point scales measuring their ability to learn new tasks and their pre-literacy skills. Of note, their expressive language and speech scores fared better– they were comparable to those of their non-separated peers.

“This makes intuitive sense,” Jee said. “In families disrupted by separation, adults are less likely to make consistent efforts to expose kids to new ideas, or to encourage reading. Without this first educational coaching from mom or dad, kids’ early learning and preliteracy skills are less likely to really blossom.