Chaos theory and complexity theory, collectively known as nonlinear dynamics or dynamical systems theory, provide a mathematical framework for thinking about change over time. Chaos theory seeks an understanding of simple systems that may change in a sudden, unexpected, or irregular way. Complexity theory focuses on complex systems involving numerous interacting parts, which often give rise to unexpected order. The framework that encompasses both theories is one of nonlinear interactions between variables that give rise to outcomes that are not easily predictable. This entry provides a nonmathematical introduction, discussion of current research, and references for further reading.
Michael S. Kelly
Task-centered practice is a social work technology designed to help clients and practitioners collaborate on specific, measurable, and achievable goals. It is designed to be brief (typically 8–12 sessions), and can be used with individuals, couples, families, and groups in a wide variety of social work practice contexts. With nearly 40 years of practice and research arguing for its effectiveness, task-centered practice can rightfully claim to be one of social work's original “evidence-based practices,” though the relative paucity of research on its effectiveness in this decade suggests that the approach itself may have become increasingly integrated into other brief social work technologies.