Your coworker has a 5-year-old son she disciplines with physical punishment frequently and as a first resort. One day she tells you physical punishment is not helping her son behave better and she is going to try a different approach. You support her decision and, citing your text, tell her that longitudinal research has discovered that receiving physical punishment as a child is frequently associated with .

A torture.

Explanation: The torture of physical punishment makes the kids more stronger and stubborn; they only master the method and it doesn't really make them change rather they conclude within them that the worst you can do is to do as usual by applying the same punishment method. Therefore, I suggest a better option which is sitting them down and speaking about the consequences of been stubborn to the parents. Make them know the advantages of been an obedient child and its benefit in the society.

the underlined phrase is an example of : understatment