The researcher behind a new study looking at rates of physical discipline against children says it's further evidence family violence can be passed down the generations.
In 2002, 77 percent of young parents tracked in a long-running Christchurch-based study smacked their kids on the bottom - dropping to 42 percent by 2017, when they were entering their 40s; while severe assaults dropped from 12 percent to 4 percent.
"We think it's good news, but... there's still a long way to go," study leader Geraldine McLeod of the University of Otago told The AM Show on Friday.
The study, published in the New Zealand Medical Journal on Friday, couldn't point to a single reason why the rates had dropped - saying it's likely a combination of "increasing maturity of the parenting sample over time (less reactive, more experienced, older parents); a cultural shift towards the unacceptability of violence towards children over the period of the study; and the law change in 2007, which prohibited physical punishment and violence towards children".
Dr McLeod said the data showed who was more likely to use physical violence to discipline their kids.
"They tended to be parents who had previously experienced, in childhood, low socio-economic status; they had experienced mental health problems in adolescence; and once they had become parents and had entered partnerships, their relationships were characterised by family harm and violence."
Some of the drop in assaults was likely down to the parents becoming more experienced as they aged.
"It's a reasonably common experience to struggle at what is often a very stressful time of life - parenting young children," Melanie Woodfield, a clinical psychologist and researcher at the University of Auckland, told Newshub in a separate interview.
"This paper highlighted that younger parents and parents of multiple children were at higher risk of using physical discipline... Older parents will have coffee groups or extended whanau, ways where they can bounce some ideas off people. Also younger parents might have a narrower repertoire or collection of different strategies they're able to use... they haven't had as much time in life to accumulate more information and pick up different strategies from different people."
Because the study followed a cohort of parents who aged 15 years over the course of the study, "it is unclear what rates of physical punishment of children would be in studies of contemporary young parents".
In conclusion however, even amongst parents in their 40s "physical punishment remains a relatively common form of child discipline despite the 2007 anti-smacking legislation and reduced public tolerance for physical violence towards children".
"There will be a proportion of people that genuinely believe physical discipline is best, and using other strategies is letting kids getting away with their behaviour and that these other strategies don't work," said Dr Woodfield.
"This is a mistaken belief."