“If it’s so great to be smart,” Dr. Kawecki asks, “why have most animals remained dumb?”

But the flies pay a price for fast learning.

Reversing the experiment showed that being smart does not ensure survival.

The ability to learn does not just harm the flies in their youth

fast-learning flies live on average 15 percent shorter lives than flies that had not experienced selection on the quinine-spiked jelly. Flies that have undergone selection for long life were up to 40 percent worse at learning than ordinary flies.

the very act of learning takes a toll. The scientists trained some fast-learning flies to associate an odor with powerful vibrations. “These flies died about 20 percent faster than flies with the same genes, but which were not forced to learn,” he said.

Forming neuron connections may cause harmful side effects.

“We use computers with memory that’s almost free, but biological information is costly,”

“It means you start out in life being inexperienced,”