Anxiety is one of most common psychopathology that psychiatrists encounter everyday in their clinical practice. Nevertheless we lack clear understanding of anxiety as well as other related psychological phenomena such as fear, panic, and phobia. In everyday life, people use these concepts without clear distinction. Even in psychiatric or psychological field, professionals differ in their definition of these concepts that makes further confusion. Ecology is a study of the animal behaviors that can be regarded as a prototype of the human behaviors. In this regard, ecology is a very useful method to understand various human behaviors and emotions including anxiety, fear and phobia. In this article, author reviews classical ecological studies of anxiety and related phenomena, This will cast certain light on our understanding of human anxiety.