However, place preference analysis in an open-field arena, which would be the equivalent of wells for zebrafish, have shown an increase in anxiety levels in 3 and 5 month old MeCP2308 mice (Shahbazian et al., 2002b) and in 8-week old mecp2-null mice (Stearns et al., 2007). This evidence concerns the gene MECP2 and Anxiety.