This thesis is about "authentic learning": learning from life-like contexts. The construct derived from the social situated approach (Lave & Wenger, 1991), has surprisingly no counterpart in cognitive psychology. The first objective of this thesis is to develop a cognitive formulation of authentic learning from classical cognitive works and recent neuroscience studies findings. The characteristically cognitive feature posited is "n-coding", the encoding of multimodal input (verbal, visual, kinesthetic, social...). To test quasi-experimentally the effectiveness of this cognitive definition, a review of the instructional literature identified Collaborative Group Problem Solving (Heller et al., 1992) as an appropriate candidate for authentic instruction in physics.