Cerebral lateralization refers to the lateralized partitioning of cognitive function in either hemisphere of the brain. Using a standard detour test, we investigated lateralized behaviour in wild-caught, female poeciliid fish, Brachyraphis (=Brachyrhaphis) episcopi, from high- and low-predation areas. Wild fish were bred and their offspring reared under controlled laboratory conditions. These laboratory-reared fish were screened in the same laterality assays as their parents. We observed differences between wild-caught females and their laboratory-reared female offspring in the pattern of lateralization (tendency to use one hemisphere over the other to process information). Conversely, the strength of lateralization (consistency of hemispherical bias) was largely conserved between generations, consistent with it being a heritable character. Both wild-caught females from high-predation sites and their laboratory-reared offspring showed stronger lateralized behaviour than their counterparts from low-predation sites. This difference in strength of lateralization is likely to provide fitness benefits to fish that occur in high-predation areas by enabling them to school and watch for predators simultaneously (dual processing). We hypothesized that the differences in the pattern of lateralization observed between species, and populations within species, are due to the manner in which they perceive and classify stimuli in the world around them. In particular, the perceived emotive content or context of a scene is likely to vary between individuals that have had different life experiences.