“Children’s play is serious business,” Dr. Spencer said. “They are getting ideas about who they are from these objects. There are messages about one’s confidence, one’s sense of self in terms of what I look like and being powerful.”

At the same time, she notes that children of different races or ethnicities do view some toys differently. “When little white girls embrace Doc McStuffins, for them Doc McStuffins is a girl, and Doc McStuffins is powerful,” Dr. Spencer said. “For a little black girl, it may be all of those things, but also that she’s black.”

Natalie Elisabeth Battles, a toddler who lives with her family in Little Rock, Ark., is so taken with Doc McStuffins that she sometimes wears a doctor’s coat to preschool. She has worn the full Doc McStuffins outfit, complete with stethoscope and thermometer, while accompanying her parents shopping, prompting other children to want a picture with her. Her father, Kevin, said they think she looks like Doc.

“To be able to identify with someone of her own race doing something positive” is valuable, her mother, Jennifer, said. “I know she’s only 3, but I think the message reaches her.”

Other mothers appreciate the character’s lifelike features.

“She has real coarse and pretty curly hair,” Kataya Smith said of her 5-year-old daughter, Kaydrian. “The Caucasian dolls’ hair is easy to manage, and I don’t want her to feel that that’s the way you need to look to be pretty. I want her to know: This is a pretty baby doll, and she has hair like me.”

Ms. Williams’s line of Positively Perfect Dolls offers a variety of hair textures and skin tones, “from vanilla crème to pecan to mocha,” she said, adding that the facial features include “full lips, noses and deep eyes” that better resemble children of nonwhite backgrounds. She added two Latina dolls, Aleyna and Camila, this year.

Despite the newfound success of a few nonwhite dolls, a decision in May by American Girl to discontinue two dolls provoked an outcry among some parents. Frustrated parents protested on the company’s Facebook page, contending that the action was a step backward.