SpongeBob SquarePants, the popular children's cartoon, can be hazardous for the attention span, a study reports.

The study from the American Academy of Pediatrics argues that fast-paced shows like the popular Nickelodeon cartoon aren't good for children.

Nickelodeon has released a statement questioning the validity of the study.

Four-year-olds who viewed the fast-paced cartoon before being tested ''were handicapped in their readiness for learning, said researcher Angeline Lillard, a professor of psychology at the University of Virginia, Charlottesville.

Lilliard randomly assigned 60 4-year-old boys and girls to one of three groups. The first group watched the cartoon about an animated sponge that lives under the sea. The second group watched a slower-paced educational cartoon that shows a typical U.S. preschooler. Third group drew with crayons and markers.

Right after the viewing, the children were given a variety of tests to assess their attention, problem-solving ability, and other skills. In one test, the researchers measured their ability to delay gratification by seeing if they could hold off on eating snacks. In another, they measured problem-solving abilities by asking children to move disks from one peg to another.

The kids who viewed the fast-paced cartoon did worse than the other two groups on the tests.

Those who watched the fast-paced cartoon were also less able than the others to delay gratification and to follow directions.

The study has limitations, including its small size.

Lillard, the lead author, said Nickelodeon's SpongeBob shouldn't be singled out. She found similar problems in kids who watched other fast-paced cartoon programming.