Attributes of a human or animal body are detected by the generation and detection of an electric field. A laminated membrane, connected to a control circuit, is placed over an electrically conductive ground-plane. An upper-mattress is placed above this for supporting a human or animal body. To improve the response of the detector, a response-enhancement-layer of a substantially electrically non-conducting compressible-material containing electrically-conductive-particles, such as carbon particles, is located between the laminated-membrane and the upper-mattress.