Toward the end of lunch, Phoenix Ferragame, 17 months old, raised both hands in front of his chest and tapped his fingertips together.
His mother smiled.
"You want more? More chips?" Gina Ferragame asked, mimicking the hand movement and then passing the bowl to her son.
For parents, hardly anything is as satisfying as being able to communicate with their children. But speech requires development of three muscle groups. Toddlers typically have motor control of their hands and fingers months sooner.
Teaching a short vocabulary of American Sign Language - milk, more, please, and a handful of other words - is so simple that parents are networking, classes are spreading, and how-to sites are booming.
Ferragame and her husband began working on basic signs with their older son, Theo, when he was 5 months old.
"I saw a response immediately," she said. "I was inspired by the fact that I could acknowledge him."
Theo, now 3 years old, verbalizes well. The other day, however, he touched his chin with his fingertips and extended the hand out and down, palm up - thank you.
"It's nice, as a mom, to hear - or see, really - please and thank you through the day," said Ferragame, 35.
Using signs both before and after the boys started to talk resulted in fewer tears and tantrums in their Mount Airy home, she said.
Children often can communicate faster with gestures or sign language than with speech, reducing their frustration at not getting what they want. And experts say that signing early can help with language development of all kinds later.
There is no consensus that early signing can bring improvement in IQ scores, as some advocates suggest. But almost everyone says that the positive parent-child interaction involved in teaching and using sign language is beneficial.
"What you are really doing is interacting with your child," said Kathy Hirsh-Pasek, a professor of psychology at Temple University who specializes in language development. "The more you interact with your children, the better their language skills are going to be, so whatever gets parents to do that, it is a positive thing."
The process is straightforward and time-consuming - lots of repetition of both words and signs like milk and eat and more when your child is thirsty, hungry, or wants more of anything. Often it takes months of consistent effort before the child begins to sign.
Hirsh-Pasek and other experts say there is no evidence that learning sign language will limit speech development, especially since the process involves both verbal and nonverbal communication.
If children were taught sign language as a true second language, it would be the equivalent of growing up in a bilingual household, said Gary Emmett, director of hospital pediatrics at Thomas Jefferson University, who often lectures on child development.
"We know that if you grow up in a truly bilingual home . . . children will start to speak about one month later, but they will speak both languages fine," he said. "It is a language-rich environment that really helps children develop."
For example, Emmett said, students who do the best in school have heard about 10 times the number of words at home as the poorest students.
Linda P. Acredolo, an emeritus professor of psychology at the University of California-Davis, is a leading proponent of teaching hearing children to sign, and her federally funded research found clear benefits.
"These kids had a jump start in language and were able to ask questions earlier and engaged with adults earlier," Acredolo said. "Of course it would benefit their intellectual development."
To study the impact of sign language on child development, Acredolo and Susan W. Goodwyn, of California State University at Stanislaus, randomly divided 103 infants into three groups. In one, parents taught them sign or gestural language; in a second, parents were encouraged to work on verbal language development; and in a control group, parents were given no particular direction about language. They were followed for eight years.
"In a significant proportion of the comparisons . . . infants who augmented their fledgling vocal vocabularies with symbolic gestures outperformed those who did not," the study concluded. No such differences were found in the group that focused on verbal skills.
The findings, published in the journal Child Development in 1993 and subsequently elsewhere, also found that the children who learned signs as infants and toddlers scored higher, on average, on IQ tests administered at age 8. "We try to not make a big deal about that because we don't want our signing to go into the pile of better-baby gimmicks," Acredolo said in a phone interview.
Acredolo and Goodwyn first recognized in 1982 that babies were using gestures to communicate things they could not verbalize. Their research ultimately led to Baby Signs: How to Talk to Your Baby Before Your Baby Can Talk in 1996, the first of several books.
They later founded Baby Signs Inc., a company that was at the vanguard of a growing global industry offering tools for parents.
"It is not necessarily new, but it certainly has exploded in the marketplace," said Jennifer Burstein, manager of speech-language pathology at Children's Hospital of Philadelphia.
Parents are drawn to the movement "not because it speeds up language, not because it makes kids smarter," Acredolo said. "It is because of the positive emotional bonds that it creates, the lower frustration levels, the ability to engage older siblings. . . . It is all these rich cultural and emotional things that are the core of the benefit."
None of that was on the mind of M. Davi Chandrasekaran when she moved from Boston to Philadelphia with a newborn in 2005.
A special-education teacher in Massachusetts, Chandrasekaran saw the benefits of using sign language to communicate with children who had autism. In Queen Village, her new mom friends asked her to show them some signs they could use with their children.
Soon she was holding classes and workshops. Then it developed into a small business, www.signwithmephilly.com. She also has been teaching sign language at Theo Ferragame's preschool, where she met the family.
"Most parents do see the immediate benefit of this bridge effect . . . 'my little one does have a lot to say' before they can verbalize," Chandrasekaran said.
"Little ones who sign milk all day long are signing it because they can - and understanding what they have to communicate is of value and will be heard."
It works the other way around, too. In Mount Airy last week, Gina Ferragame made the sign for sweet, and then opened and closed her right fist, for milk.
Theo jumped up and ran to the kitchen, with Phoenix toddling behind.
Yeah! Time for an extra-special treat: chocolate milk.
Numerous books and websites offer help in teaching infants sign language. Among them:
Common signs for kids, with video illustrations: www.signwithme.com
An extensive American Sign Language dictionary: www.lifeprint.com