Association between DRD4 gene polymorphism and personality variation in great tits: a test across four wild populations. by Korsten, P, Mueller, J, Hermannstädter, C, Bouwman, K, Dingemanse, N, Drent, P, Liedvogel, M, Matthysen, E, van Oers, K, van Overveld, T, Patrick, S, Quinn, J, Sheldon, B, Tinbergen, J, Kempenaers, B