Although there is some evidence that females assess male cognitive ability when choosing a mate, the effect that cognitive ability has on survival and mating preference remain unclear. Many questions need to be answered to be able to better appreciate the implications that cognitive traits may have in mate choice. Some discrepancies also need to be resolved. For example, in 1996, Catchpole suggested that in songbirds, females preferred males with larger song repertoires. Learned song repertoire was correlated with the size of the High Vocal Center (HVC) in the brain; females may then use song repertoire as an indicator of general cognitive ability. However, a more recent study found learned song repertoire to be an unreliable signal of cognitive ability. Rather than a general cognitive ability, male songbirds were found to have specific cognitive abilities that did not positively associate.