Attraction, love, attachment, commitment — terms that form the core of some of the articles that we feature in this issue. However, after close scrutiny, you will see that we were not unduly influenced by the impending Valentine's Day when compiling it. For example, the Highlights include an article on growth cone attraction and repulsion, both of which are necessary to coordinate axon guidance in Drosophila. A more anthropomorphic interpretation of the 'attraction' theme is provided by our 'In the News' column, which looks at the response of the international press to a recently published study on the neurological basis of romantic love. This study showed that being in love is associated with the activation of brain areas implicated in addiction. And the molecular basis of addiction is precisely the subject reviewed by Eric Nestler. Specifically, he describes the molecular mechanisms that could underlie some of the behavioural changes associated with chronic exposure to drugs. A different kind of behavioural change is also relevant to the neurobiology of social attachment, as Insel and Young discuss in their Perspective. Here they try to explain, among other things, why certain species of vole commit themselves to a single partner. Commitment is also the subject of Livesey and Cepko's article on cell-fate determination; they propose a model to explain how progenitor cells become committed to specific lineages in the developing retina. Last, for those who prefer not to let their heart rule their head, there is Robert Plomin's Perspective on the genetic basis of g, a measurement of the overlap between individual differences in cognitive processes in humans. He proposes the use of rodent models to study g, a viewpoint that is sure to provoke lively debate among scientists in this field.