The opponents state that the baby needs to learn soothing on their own. The caregiver has to control basically everything without any concern whatsoever to the baby's needs or wants. So, where do these ideas originate?
In the beginning of the 20th century when psychology only begun to unfold its wings, a powerful movement started in America whose objective was to purify the new science and investigate only those subjects that are scientifically measurable. This approach's focus of attention was the behavior, at first only ignoring feelings, thoughts, evaluations and anything which can be reached by the sinful introspection. Later they denied the latter's mere existence; even consciousness fell into this category.
What they discovered was incredibly trainable learning machines with consequent stimuli-response sequences with wide range of behavior that can be taught to lab rats and also taught to humans.
This is hardly a surprise. Behavior ecologists claim that one of the species specific characteristics for humans is the incredibly high capability of learning. From the evolutionary point of view, the lower a species is on the evolutionary ladder, the more its genetic inheritance leads its behavior. The higher a species is in the evolutionary ladder, the more learning controls the behavior.
Even though capability of learning can be the highest among people compared to the animal kingdom, it is a mistake to believe we don't have anything else like feelings, instincts or inner motivation. The Problem With 'Mommy Porn'
So which approach is valid and which one's practical advice is worth to follow? Pease read it here in Part 2!