In recent years, “lie flat” is a buzz word which describes a special psychological state of some people, but its animal behavioral models are lacking, and its psychological meaning and mechanisms remain unclear. Lack of motivation under certain conditions may be one of the key psychological characteristics for “lie flat”. In this study, a novel rat behavioral model of “lie flat” was designed and was used to explore the possible effects of dopamine receptor in the nucleus accumbens on motivation deficiency in “lie flat”.