The way of a mother with her young is arguably the most intimate of all mammalian relationships. In large measure, this is due to the mechanics of anatomy and physiology. Mothers come equipped with the biological ability to conceive, gestate, give birth and lactate. There is a physical connection between mother and child in which the mother is the literal lifeline for the child.
However, the task of motherhood is a great deal more complicated than these physiological mechanics. According to evolutionary scientists, offspring are not all capable of taking the nurturing given them by their parents and translating that nurturance into the long-term preservation of parental genetic material. As a result, maternal effort may not be allocated in equal measure to all the children of one mother.
From this point of view, mothers have developed mechanisms based on motivation, which regulate their decisions as to how much maternal effort they might invest in a particular child. In part, this may depend upon the attributes of the child, material circumstances and social standing. Another salient factor may be the age of the mother and her point along the path of lifecycle development.
It is difficult to measure the ways that mothers invest and allocate their attention to their children. For one thing, the offspring by definition have conflicting interests and may vie for or avoid maternal attention using different methods at different times. These variables cannot be factored into the equation with any measure of precision.
As well, it is normal for a certain level of conflict to exist between parents and offspring as the nature of a species with the capability of sexual reproduction. This is due to the asymmetry of the mother/child relationship. A mother is related in equal measure to each of her offspring. However, each child has a closer relationship to itself than to its siblings.