If your toddler is having trouble building her vocabulary, you'll want steer him toward the word "dog" rather than, say, "aardvark."

It may be common sense but now there's a growing body of scientific research to back it up, says psychology professor Leslie Altman Rescorla.

Rescorla, the director of the Child Study Institute at Bryn Mawr College, presented research on late talkers in the United States and around the world this past weekend in Vancouver, British Columbia, at the American Association for the Advancement of Science's annual conference.

Rescorla said that recent studies of children's language development in Greece, the Netherlands and South Korea echo findings she published in 2001 - that whether a child is slow to learn language or learns language at an average rate, there are certain commonly used words that she is likely to know, and when working on language intervention for late talkers, Rescorla said, it's good to focus on such words when building a basic vocabulary.

Based on her own research and that of collaborators in other countries, Rescorcla compiled a list of the 25 most commonly used words and expressions by children at age 2. They are:

• mommy
• daddy
• baby
• milk
• juice
• hi/hello
• ball
• no
• yes
• dog
• cat
• nose
• eye
• banana
• cookie
• car
• hot
• thank you
• bath
• shoe
• hat
• book
• all gone
• bye bye
• more

Rescorla said children are considered late talkers when they say fewer than 50 words at the age of 24 months. Such delays may be symptomatic of hearing problems, an autism spectrum disorder or another developmental disability.

Her research on children with language delays - and no other disabilities - showed that late talkers were "functioning at the normal range" by about age 4 or 5.

"The important point is they're not learning language in some very unusual way, they're just learning it later," she said.

A long-term study by Rescorla of late talkers in affluent Philadelphia suburbs found that by age 17, the teens' performance was at or above average, though they still lagged behind the language skills of their privileged peers.

"It's the difference between being normatively OK at the population average and being comparable to the people in your demographic group," Rescorla said.