While there have been studies attempting to disprove Chomsky, Marcus states that, "An intriguing possibility is that the capacity to recognize recursion might be found only in species that can acquire new patterns of vocalization, for example, songbirds, humans and perhaps some cetaceans." This is in response to a study performed by psychologist Timothy Gentner of the University of California at San Diego. Gentner's study found that starling songbirds use recursive grammar to identify “odd” statements within a given “song.” However, the study does not necessarily debunk Chomsky's observation because it has not yet been proven that songbirds have the semantic ability to generalize from patterns.