There is often a strong biological component to behavioural issues.

Behaviour problems in children, especially aggression and defiance, don’t get a great deal of sympathy, said Dave Anderson, a psychologist who is senior director of national programmes at the Child Mind Institute in New York City. 

“For a child to get better requires just as much empathy and scaffolding as for a child who might be depressed, but behavioural issues inspire nowhere near as much empathy.”

There is a persistent belief that these behaviours reflect poor parenting, he said, but in fact, there is often a strong biological component to behavioral issues.

“If you’re going to have persistent behaviour problems involving aggression and defiance, it’s already elevated at 2,” said Michael F. Lorber, a senior research scientist with the Family Translational Research Group at New York University.

In a study published last year in the Journal of Pediatrics, Dr. Lorber and his colleagues looked at 477 children from 6 to 24 months of age, asking their mothers to report on how often in the past month the children had shown specific behaviours ranging from kicking and hitting to pulling hair, biting and even hurting animals.

These behaviours were very common, with some actions (hitting or smacking someone) much more common than others (hurting animals). The prevalence of the behaviours tended to increase over time, with hitting peaking at 18 months, and kicking and pushing, as well as throwing objects at people, peaking at 20 months. “Eight of 10 kids were hitting and smacking at 18 months,” Dr. Lorber said. “The terrible twos started before 2.”

Not only were more toddlers hitting as they got older, but they were hitting more frequently.

On the other hand, hair-pulling decreased with age, as did scratching, and the researchers speculated that the increased incidence of those behaviours among the younger children may reflect the close contact they have, since they are usually being held.

The researchers suggested that pediatricians can reassure parents that these behaviours are normal in small children, but also guide parents, right from the beginning, in setting limits and responding in ways that may help - redirecting or distracting a child - rather than by punishing the child with anger, yelling or spanking.

Though these behaviours are seen in almost all children, those toddlers who act aggressively more frequently and consistently may need more help - and so may their parents. “These behaviours are not inconsequential,” Dr. Lorber said. “Kids who are more aggressive also tend to be more tantrummy, more irritable.”

Dr. Anderson said  parents should set up clear expectations before a problem develops, thinking about how to manage getting ready for school the next morning, for example, if today did not go well. And they should offer specific positive feedback for positive behaviours, rather than worrying that they will “jinx” those good behaviours.

If a child is having significant behaviour problems, parents should be ready to ignore minor misbehaviour, he said, such as verbal disrespect or whining. So pick your battles, and don’t give in to the idea that a big punishment is the way to go. “With aggression, lots of parents have a ‘go big or go home’ approach: My child picked a fight, so no play dates, no TV,” privileges rescinded indefinitely, Dr. Anderson said. “The reality is that big punishments do not translate to better behaviour.

Instead, punishments should be immediate, consistent and used in small doses; parents should look for ways to remove a privilege for a short time, and establish clear expectations for better behaviour. 

Thus, if a child picks a fight with another child at school, a parent might impose a specific consequence (such as no screens for two days), offer a clear discussion of keeping your hands to yourself, and go over some alternative strategies for moments of frustration: take a break, tell a teacher, interact with another peer. And then, having defined the good behaviours, the parents - and perhaps the teacher as well - need to look for occasions to draw attention to those behaviors.

“The moment we see him be mildly frustrated but take a break, whether consciously or unconsciously, we need to catch him,” Dr. Anderson said, and tell him he did the right thing.

The New York Times