Two groups of fish, the Gymnotiforms of South America and the Mormyrids of Africa, have independently evolved the ability to produce and detect weak (on the order of millivolts/cm) electric fields. These fish use their electric fields in a large number of behaviors, including the detection and characterization of objects in their environment and in social interactions. The electric behaviors of different species vary widely, and several species have independently evolved particular behaviors.

In many ways these fish are ideal for the study of the neural basis and evolution of behavior. The behavioral signals are easily monitored and reproduced. The behaviors are complex but are often highly repeatable and robust. Many species of these fish thrive and breed in captivity, and are readily available in the wild. The diversity in species and the independent convergent evolution of certain behavioral characteristics provide an unusually strong background for comparative studies and the examination of the complex relation between neural and behavioral evolution.

Behavioral experiments have revealed a complete sensory algorithm for the control of a behavior in Eigenmannia, the jamming avoidance response, usually known as the J.A.R.

Using the natural behavior as a tool for understanding the neurobiological mechanisms that control the JAR, researchers have eluctidated the neural codes in the complete CNS circuit necessary for its control, from the primary sensory afferents to the motor units. It is arguably the best understood neural circuit for the control of a behavior in any vertebrate species. This has been possible, in part, because electric behaviors like the JAR operate normally in immobilized fish, thereby allowing intacellular recordings from CNS neurons during natural behaviors.