Accommodation is a theory that breaks down the ongoing, interactive nature of discourse while Acculturation is a model for L2 learning and communication. Although they have different purposes, they do hold an important role in the field of linguistics.
Howard Giles's Communication Accommodation Theory, also known as Interpersonal Accommodation Theory, argues that
…accommodation is to be seen as a multiply-organized and contextually complex set of alternatives... It can ...achieve solidarity with or dissociation from a conversational partner, reciprocally and dynamically (Giles & Coupland, 1991: 60-61).
This tenet is quite easy to understand; individuals monitor their verbal communication depending on variables such as a) the person with whom the person is talking, b) the origin of the discourse and, c) the need to create distance, proximity, or identity.
The model also shows that individuals are not mere recipients of verbal communication, but interactive participants whose brains are in a consistent state of decision-making. Decisions during discourse include convergence, which entails changing your speech to match that of the person with whom you are speaking (rate of speech, intonation, use of pauses) and divergence, which is the choice to emphasize your unique way of speech so that you can create a distance from others; sometimes when people imitate or "fake" accents to create identity is a form of either divergence or convergence, depending on the goal.
Conversely, J. H. Schumann's Acculturation Model of SLA is mainly used show how blending into the target culture ensures successful L2 learning. In Schumman's model there are eight variables for student success:
1) Social dominance: L2 students may not want to learn a target language from a culture that is considered superior to their own; it makes the learner feel inferior.
2) Assimilation, preservation, and adaptation: The choice to take in the target culture, or preserve one's own.
3) Enclosure: The degree to which the L2's target society resembles their own will facilitate learning.
4) Cohesiveness: If the L2 is too culturally-bound to his peers the learning will be harder to accomplish.
5) Size: L2 learning is to be done best in smaller groups.
6) Congruence: The more similar the target culture is, the most likely that the learning will occur.
7) Attitude: If the L2 feels resentful or negative about the target culture the learning may not happen.
8) Intended length of residence: Also entails consistent exposure to the target language.
The most obvious similarity between Accommodation and Acculturation is that both, the theory and the model respectively, show that the process of verbal communication is extremely intrinsic, three-dimensional, and complex. They also contend that choices are made at all times during discourse, and that there are variables in language usage that can make or break the communication process.
Their main difference is that they serve different purposes. Accommodation is a tendency in language usage, while Acculturation is the study on how blending into the target culture may produce more L2 learning success. As a model, Acculturation aims to establish a correlation between individual behavior and the phenomenology of social change. Contrastingly, Accommodation is a theory that is generally accepted as a fact.