 Although parents and other advocates of spanking often claim that spanking is necessary to promote child discipline, studies have shown that parents tend to apply physical punishment inconsistently and tend to spank more often when they are angry or under stress.The use of corporal punishment by parents increases the likelihood that children will suffer physical abuse, and most documented cases of physical abuse in Canada and the United States begin as disciplinary spankings.If a child is frequently spanked, this form of corporal punishment tends to become less effective at modifying behavior over time (also known as extinction).