The so-called "terrible twos" are so much a part of the American lexicon that even people without children know that 2-year-olds and tantrums are synonymous.
What, then, of the threes? Clearly forewarned about the twos, parents often expect to endure one trying year and then move on to an age where "no" is no longer the child's favorite word, where outbursts are no longer the norm.
But that's not where the testing ends. As it turns out, "threes" can be a whole lot more terrible than "twos."
"Three-year-olds are more challenging than 2-year-olds because developmentally they're so much more sophisticated than they were at 2," said Dr. Brenda Hussey-Gardner, an author of a parenting book and assistant professor of pediatrics at the University of Maryland School of Medicine.
"It's labeled as the terrible twos because it's a hard time for parents. For many parents, 3 is harder than 2."
It's a lesson most parents who have been down that road have learned -- and often keep to themselves. The first time through, parents are just not prepared. When they mention their woes aloud, an experienced mom might let them in on the secret -- that 3 can be even harder than puberty and the teen years. The good news: The nagging, whining and fierce temper tantrums are perfectly normal.
No one told Keisha Maldonado what she was in for. Her oldest son, now 6, was "being horrible" at 3. She brought up her worries at church one day as she confided in a girlfriend with six kids.
"She told me there is such a thing as the terrible threes," Maldonado said recently as she and a friend pushed strollers at the Owings Mills Mall.
"She's my third," Maldonado said, gesturing toward daughter Haylee, who will be 3 next month. Haylee was quietly turning the pages of a book. "I've never had a problem with the twos. It's when they turn 3; they completely change. That's when I've had the hardest time.
"That's when they've thrown their temper tantrums. They don't want to hold your hand crossing the street. They want to do everything themselves. They want to be independent, but they can't be at that age."
By comparison, babies can seem easy. Sure, they cry a lot and demand food in the middle of the night, but the labor involved in feedings and diaper changes and holding an infant for hours on end is mostly physical.
When the child reaches 18 months to 2 years, parents and experts agree, they demand a different kind of labor -- an intense mental energy.
Parents have to help a toddler navigate her frustration with not being able to express herself with words. They also have to make sure she explores the world in a safe way. As she gets older, parents encounter the endless questioning and the testing behavior that comes at 3 and beyond.
It's the "beyond" that even some experts leave out. Consider this statement from the Web site of no less an authority than the American Academy of Pediatrics: "With your child's third birthday, the `terrible twos' are officially over and the `magic years' of three and four begin."
Most moms know better.
"The wives tale is the `terrible twos' and the `troublesome threes,'" said Robert F. Myers, a child psychologist in Southern California. "It's interesting that it's been scaled down to think by the age of 3, all of this will go away. It's around 4 and into 4 that you would expect, based on where they are developmentally, to see some changes. Four is the light at the end of the tunnel."
Starting at about 18 months, children begin to realize that they're not physically connected to their mothers. At 3 or thereabouts, Myers and others said, they are still discovering their place, constantly testing the limits set by their caregivers.
Tantrums can become lengthy outbursts because the children have new skills -- including a fierceness of will that makes it hard to distract them from their fits. They're bigger, they're smarter and they remember things -- not just nursery rhymes and simple songs, but also promises made by parents -- and sometimes not kept.
"They're more sophisticated in how they fight their battles," said Dr. Martha Farrell Erickson, a psychologist at the University of Minnesota and a grandmother of a 3-year-old. `They still need to fight those battles to discover the limits of their own power. They're trying to establish that they have a separate sense of self. They're independent. They want to be in charge."
One issue is how parents react to these no-longer fully dependent creatures. Suddenly, their preschoolers can carry conversations, run and jump, use the bathroom, navigate the stairs with ease and cut things with scissors -- so they seem much older than they are.
"As such, parents have higher expectations," Hussey-Gardner said. "We skip threes and think of them as a kindergartner. Cognitively, they're getting pretty darn sophisticated, but they're not 5. They're still little.
"Three is a real transition between baby and preschooler. I think 4 and 5 are easier. They start to understand things better."