It is common to use mechanical language to describe this process, partly because our society has been brought up on the mechanical metaphor that equates the process of cognition with the process of a computer. You can see this in neurobiology, too, when you read about neurons 'sending messages,' or 'communicating.' It's very much consistent with the notion of cables transferring bits of data and information back and forth. Unfortunately, this language is also used in Cognitive science. Hypothetical constructs used in Memory research include: encoding, storage, retrieval, and information processing, for example. Although handy, they are misleading. We don't have 'information' in our heads-we have patterns of neuronal firing, and using these mechanical words, exclusively, might prevent us from thinking better about our experiences. In fact, have you ever tried to define information? It's not easy. My favorite is: information is a difference that makes a difference. The point is that since we often think in terms of metaphors, we can loose sight that they are just metaphors and start reifying them-treating the metaphors as if they were real. Differences that make differences.
Of course, who gets to determine what makes a difference? We do, and we do so through language. Piaget's use of language is much different from the mechanical language mostly because he operated from an organic metaphor view point. For instance, when you realize that neurons aren't communicating as much as they are *coordinating,* you get a very different view of our cognition and our biology. The difference is that instead of people acting as machines, you can see people as organisms adapting and coordinating with their environment.
This notion of coordination may be useful to understand Piaget's Equilibration theory. Assimilation and Accommodation are both a means to coordinate with the environment. Assimilation is more quick and basic. It is akin to asking a question of the environment: "Is my action useful here?" with the assumption that it is. This is important. It's sort of a 'shoot first, ask questions later.' It is an INSTRUMENTAL question as it tends toward the practical.
Accommodation, ideally, is what takes place if the answer to the above is 'no,' thus requiring a change in action (we might call this development). Granted, I'm describing this at the level of the sensorimotor stage, but it works as well if you substitute 'action' with 'understanding.' In fact, many would argue that the difference between 'action' and 'understanding' is a consequence of a misunderstanding. There is a reductionist tendency to separate emotion and cognition from behavior (in other words, feeling, thinking, and doing are completely different and unrelated and this is why we need different words like 'understanding' vs 'action). What I am suggesting is what we call understanding, in general, is really only a certain type of action, and that this action is an attempt to coordinate with the environment.
I tell the following story in my intro class as a way to get the gist of this Equilibrium process. I used to work at Highline CC. In Feb of 2001, we had a major earthquake in the south Puget Sound region. At first I had no idea it was an earthquake mostly because I was trapped in an assimilative loop.
The reason has to do with the construction of our building-a 2 story, square shaped structure made of concrete and steel that enclosed a small garden. I was upstairs in my office with another adjunct faculty member at the time. At the end of the cement hallway was another professor (I'll call him Bob) who was overweight and walked with a limp. Whenever he would come by my office, the building would shimmer under each of his steps.
Well, when the earthquake struck, I thought "Bob must have fallen down." This is classic assimilation. I used what I know about the building (shakes with Bob) and made the experience fit my thinking.
But the noise and shaking became more intense, so I thought "Bob has fallen and is now rolling down the hall." That is as far as I got before my officemate realized the truth. I followed her out the building.
Through my thoughts and action, I was asking the universe if my understanding was useful. It wasn't. Once my friend called it an earthquake, it was easy for me to switch to "asking" a better question by leaving the building. That switch would be an Accommodation. And what really blows my mind when I think about it, is that I accommodated to the language of my office mate, not to the earthquake. In fact, for me there was no earthquake until my officemate articulated it. (Yes, there was something going on, but I didn't 'know' what it was).