A colleague of mine recently asked me to explain the difference between bottom-up and top-down reading strategies. I feel a need to add the interactive approach to reading to these descriptions, as well.
Essentially, bottom-up, top-down, and interactive approaches to reading are the theoretical models used to describe how print is processed. Each are described below.
Bottom-up strategies (or bottom-up processing): Bottom-up strategies incorporate the lower-level reading processes that teach students to construct meaning from the most basic units of language, including letters, letter clusters, and words. Students make meaning of a text by building on a foundation of analyzing the smallest units of meaning. Bottom-up reading strategies begin with letter-sound correspondences (the bottom) to achieve comprehension (the top). Bottom-up processing begins with letters and sounds, building to morpheme and word recognition, and then gradually moving to grammatical structure identification, sentences, and longer texts. A phonics approach to teaching reading supports bottom-up processes. Phonics is a method to facilitate students' access to text to ultimately lead to comprehension.