A fundamental issue for the high temperature superconducting cuprates is how various degrees of freedom, e.g. lattice and spin, compete or cooperate as basic ingredients of the superconductivity. In this talk, I will address this issue based on a detailed momentum, doping and isotope dependent study of the quasiparticle dynamics in double layer Bi₂Sr₂CaCu₂O_8+δ high temperature superconductor, by using angle resolved photoemission spectroscopy. The nature of the electron-lattice interaction is discussed on the basis of different theoretical models, and a physical scenario that puts the physics of high Tc in a similar framework as spin Peierls systems is discussed.