Lanthanum cations are well known for their inhibitory actions on calcium channels, and calcium cations are indispensable for the development of brain. Lanthanum may interfere with the developing central nervous system. Detour learning task in chicks is an excellent model to study the development of central nervous system. In the present study, we examined the effects of lanthanum chloride exposure on the development of spatial cognition using the detour learning task. The data suggest that the chicks injected with lanthanum chloride (10 or 5 mM) had significantly delayed the response latency of detour learning but not the chicks injected with lanthanum chloride (1 mM). The effect of lanthanum exposure on the development of spatial cognition is dose relative.