Olfactory cues play essential roles in psychosocial development. For instance, mother-infant bonding and mate selection are shaped by early olfactory experience; studies also show olfactory deficits associated with a large range of disorders such as autism, depression, anxiety, schizophrenia, obsessive compulsive disorder and various psychopathologies and lead to the hypothesis that disabilities in olfactory perception contribute to clinical aspects of these diseases. And yet, the olfactory system remains poorly understood and we are currently unable to explain, much less remediate, olfactory dysfunctions associated with serious medical and social consequences. Much of this lack of understanding can be traced to the extraordinary complexity of olfaction system with hundreds of genes uniquely expressed in the olfactory system of humans and other mammals. Fortunately, zebrafish, which have proven to be valuable models for understanding many other systems in our body, can also be exploited to better understand the sense of smell. While zebrafish share many genes and much of its basic neuroanatomy with humans, they have an olfactory system with only about 1/10 as many receptor genes and processing units (glomeruli) as found in most mammals. Here we propose to use zebrafish to examine how the ability to detect, discriminate and remember odours changes during early development. We will focus specifically on how early experience with odours changes both the ability to smell and the underlying circuitry of the brain. We anticipate that the results of these studies will help us better understand not only how we smell but also why odours that we first encountered as children can elicit powerful memories and shape social behaviours when presented decades later. Tools and concepts developed in this research will, in turn, permit us to examine how and why olfactory dysfunction contributes to the development of psychosocial problems associated with the disorders listed above.