For decades, child psychologists have warned parents against giving kids a spanking.

"Based on 20 years of research on physical punishment, it is recommended that it should not be used on children of any age," said Tracie Afifi, an associate professor who published a study in the journal Pediatrics in 2012.

Spanking or slapping children may increase the odds they will develop mental health issues in adulthood, Afifi said.

Newer research in the Journal of Family Psychology uncovered a pattern of spanking or hitting children in 15 families in which mothers signed up to strap audio recorders on their arms. The 15 were part of a total of 33 families in Dallas who agreed to the study.

In the 15 families that punished their children, there were 41 separate incidents of spanking or hitting over a six-night period. After being hit, the children were misbehaving again within 10 minutes of 75 per cent of the incidents.

Originally, the research was designed to measure the number of times children were yelled at, and how effective the audio recorders were as a research device.

Study author George Holden, a professor of psychology at the Southern Methodist University in Dallas, said the number of spankings surpassed what the parents had self-reported.

"Parents are hitting their children over trivial misdeeds and some of the moms are doing it a lot more than the self-report data ever identified," Holden said.

Holden designed the study to focus on evening behaviour because he has often heard mothers refer to early evening as the "hell hour."

"It's a very difficult time, trying to pull dinner together and deal with the kids, and I thought it would be likely to elicit anger. It's stacked up against harmonious interactions."

Nationwide, 70 to 90 per cent of parents hit or slap their children, Holden said.