The jamming avoidance response is a behavior of some species of weakly electric fish. It occurs when two electric fish with wave discharges meet – if their discharge frequencies are very similar, each fish shifts its discharge frequency to increase the difference between the two. By doing this, both fish prevent jamming of their sense of electroreception.

The behavior has been most intensively studied in the South American species Eigenmannia virescens. It is also present in other Gymnotiformes such as Apteronotus, as well as in the African species Gymnarchus niloticus. The jamming avoidance response was one of the first complex behavioral responses in a vertebrate to have its neural circuitry completely specified. As such, it holds special significance in the field of neuroethology.

The jamming avoidance response (JAR) was discovered by Akira Watanabe and Kimihisa Takeda in 1963. The fish they used was an unspecified species of Eigenmannia, which has a quasi-sinusoidal wave discharge of about 300 Hz. They found that when a sinusoidal electrical stimulus is emitted from an electrode near the fish, if the stimulus frequency is within 5 Hz of the fish's electric organ discharge (EOD) frequency, the fish alters its EOD frequency to increase the difference between its own frequency and the stimulus frequency. Stimuli above the fish's EOD frequency push the EOD frequency downwards, while frequencies below that of the fish push the EOD frequency upwards, with a maximum change of about ±6.5 Hz. This behavior was given the name "jamming avoidance response" several years later in 1972, in a paper by Theodore Bullock, Robert Hamstra Jr., and Henning Scheich.

In 1975, Walter Heiligenberg discovered a JAR in the distantly-related Gymnarchus niloticus showing that the behavior had convergently evolved in two separate lineages.

Eigenmannia and other weakly electric fish use active electrolocation – they can locate objects by generating an electric field and detecting distortions in the field caused by interference from those objects. Electric fish use their electric organ to create electric fields, and they detect small distortions of these fields using special electroreceptive organs in the skin. All fish with the JAR are wave-discharging fish that emit steady quasi-sinusoidal discharges. For the genus Eigenmannia, frequencies range from 240 to 600 Hz. The EOD frequency is very steady, typically with less than 0.3% variation over a 10-minute time span.

If a neighboring sinusoidal electric field is discharging close to the fish's EOD frequency, it causes interference which results in sensory confusion in the fish and sufficient jamming to prevent it from electrolocating effectively. Eigenmannia typically are within the electric field range of three to five other fish of the same species at any time. If many fish are located near each other, it is beneficial for each fish to distinguish between their own signal and those of others; this can be done by increasing the frequency difference between their discharges. Therefore, it seems to be the function of the JAR to avoid sensory confusion among neighboring fish.

To determine how close the stimulus frequency is to the discharge frequency, the fish compares the two frequencies using its electroreceptive organs, rather than comparing the discharge frequency to an internal pacemaker; in other words, the JAR relies only on sensory information. This was determined experimentally by silencing a fish's electric organ with curare, and then stimulating the fish with two external frequencies. The JAR, measured from the electromotor neurons in the spinal cord, depended only on the frequencies of the external stimuli, and not on the frequency of the pacemaker.

Most of the JAR pathway in the South American Gymnotiformes has been worked out using Eigenmannia virescens as a model system.