a trend toward significanceP = 0.077
Again, when all birds were considered individually, neither hemisphere showed a significant correlation between the quality of song imitation as measured by SI and new neuron density in NCM, although there was a trend toward significance in the left hemisphere only (n = 21; left: r 2 = 0.155, P = 0.077; right: r 2 = 0.055, P = 0.305).