Although rats in general were the species of choice for use by experimental psychologists to study behavior, mice have been the preferred animal for behavior geneticists since at least the 1940 s. In addition, the adaptation of behavioral assays and the development of new methods have confirmed the mouse as one of the most preferred experimental systems to learn more about the genetic underpinnings of behavior and associated phenotypes. Martien Kas described the currently underlying scientific rationale. Precise measurement of a well-described behavioral trait across a GRP will lead to the identification of associated genes and genomic regions. In the next step these genes can be used to find homologous genes and pathways that contribute to the development of neuropsychiatric disorders in humans. The translational value of this interspecies genetic approach was nicely exemplified in a study in which a QTL for avoidance behavior in mice was related to bipolar disorders in humans (de Mooij-van Malsen et al. 2009 ). In a similar approach, Iris Hovatta used a cross-species neurogenomics comparison to correlate brain region-specific gene expression patterns and anxiety-like behavior in mouse GRPs to polymorphisms in the Finnish population for anxiety disorders (Hovatta et al. 2005) . The mouse genes allowed identification of potential candidate genes in humans who predispose to anxiety disorders. Paul Franken presented studies on the identification of genetic traits that influence homeostatic and circadian aspects of sleep, and the electroencephalogram in the BXD GRP and in inter-and backcross panels of mice (Shaw and Franken 2003) . Several genes that play a decisive role were identified, and further phenotyping of the extended BXD GRP is planned. Eero Vasar and Sulev Kõks described the role of the Wfs1 gene in knockout mice for anxiety behavior, an altered response to morphine and the release of striatal dopamine (Koks et al. 2009; Luuk et al. 2009 ). Ewelina Knapska reported the use of a highly sophisticated cage system, IntelliCage, to automatically record a number of different complex behavioral traits in mice (Jaholkowski et al. 2009 ). Mice can be housed in social groups but nevertheless tested individually. Ryszard Przewlocki reported on a systematic study on various inbred mouse strains to identify genetic determinants of alcohol and drug addiction (Piechota et al. 2010) . Combining these studies with comprehensive gene expression analyses revealed that glucocorticoid receptor-activated gene expression pathways play an important role. Wim Crusio studied behavioral traits in learning and related them to brain anatomy (Crusio and Schwegler 2005) . Thereby, the extent of neuron projections in the hippocampus could be correlated to more efficient learning capabilities and these two phenotypes are very strongly correlated genetically. Guus Smit gave an overview on a collaborative effort in the Netherlands in which several research groups have determined various behavioral phenotypic traits and QTLs in a commonly used BXD population (Loos et al. 2009 ). Also, they established a mouse facility in which they are using automated screening cages with sophisticated video recording and analysis.