How do I know this? Because I'm one of them!
And ... good for you!
The specific example was with respect to talking to infants - that talking to children who do not yet have the power of speech makes an enormous difference in the development of verbal and cognitive ability. Rich infants heard an order or two more words per day than poor infants due only to the fact that poor parents didn't know that it was important. There was no intent to neglect, just ignorance.
The overwhelming majority of parents want to be good parents, some just need better information on how to do it.
http://www.ted.com/talks/steven_pinker_chalks_it_up_to_the_b...
The cause is that in the first few years of life we lose unused connections between neurons. If a child does not have a primary care giver, then a lot of the connections lost are necessary for proper social and cognitive development, and the child is impaired for life in ways which are clear in the physical structure of the brain.
This has been known for decades, yet still periodically someone somewhere that still has orphanages rediscovers this basic fact. (The most recent example that I heard about involved children in Romania.)
Sorry, I don't have time to watch an entire video. Is there a transcript?
This research basically disproves that, saying that nurturing and loving upbringings have that effect, while cold tough upbrinings are detrimental.
Having that kind of evidence is extremely helpful—either parents who read it might change their mind, or it could be discussed in parenting groups.
Either way, the point is that it's scientific evidence. People may eventually come around to it, leading to a better world with more nurturing parents and better childhoods and therefore better adult lives for a great many people.
Will it happen soon? No. These beliefs are often so dogmatic and almost religious in nature that it's unlikely to affect the people who hold them. But maybe it will reach their children.
My mom studies animal behavior in dogs (read: she's a really good dog trainer) and the science behind positive reinforcement methods is overwhelming. Yet, people still use negative methods and get burned for it... more agressive behavior, less predictable behavior, conditioning that doesn't stick, and long-term trust issues with their dog. Positive methods are self-reinforcing, while negative methods require constant reinforcement to remain effective; at the same time, positive methods build your relationship with the dog and create a happier, healthier animal, while negative reinforcement causes extreme unintentional side-effects in both the long and short-term.
It's the same with kids; we're just animals in the end and the behavioral science applies nearly exactly the same. It's a no-brainer and proven by science, but for some reason people still think you need to whip a kid with a belt to teach them to behave.
Merely "not spoiling your child" is just a minor parenting choice; and surely you can't always be positive when there have to be negative consequences. But I'm talking about far worse negativity and lack of nurturing that's far worse and really is a core belief of a good portion of society.
Think of questions like: - Should a parent take a promotion that will result in longer work hours? - Is it worth taking a compensation hit for a parent to stay home or reduce working hours? - Should a parent place a child in a daycare or hire a sitter/nanny? - To what level should grandparents be involved in the raising of a child?
All of these questions have multiple answers that have different impacts on your ability to support yourself and nurture your child. It's a balance.