luzr: Learning (or change) doesn't mean arbitrariness, adaptivity can and should be as lawful as math. Only few responses to changing context are the right ones, apparent "flexibility" of adaptive behavior is the ability to precisely select right responses to any of the huge number of possible circumstances, not uncontrollable variation that leads to all kinds of unpredictable consequences.

From "The Psychological Foundations of Culture" by Tooby & Cosmides:

Literally, plasticity, or flexibility, is the simple capacity to vary in some dimension. The more dimensions of possible variation, the greater the "plasticity." Hence, a lump of clay is very plastic with respect to shape (although not with respect to substance, density, and so on). Similarly, there is an infinite number of ways that humans and other animals could potentially act. The difficulty lies in the fact that the overwhelming majority of behavioral sequences would be lethal in a few hours, days, or weeks. The set of behaviors that leads even to temporary individual survival -- let alone to reproduction or design-propagation -- constitutes an extremely miniscule subset of all possible behavioral sequences. Thus, the property of freely varying behavior in all dimensions independent of conditions is not advantageous: It is evolutionarily and individually ruinous.

Accordingly, to be endowed with broad behavioral plasticity unconnected to adaptive targets or environmental conditions is an evolutionary death sentence, guaranteeing that the design that generates it will be removed from the population. Designs that produce "plasticity" can be retained by selection only if they have features that guide behavior into the infinitesimally small regions of relatively successful performance with sufficient frequency. In reality, terms such as flexibility or plasticity are implicitly used to mean something very different from the simple "capacity to vary." They are implicitly used to mean the capacity to adjust behavior (or morphology) as a coordinated response to the specifics of local conditions so that the new behavior is particularly appropriate to or successful in the specific circumstances faced.