Negative hyperconjugation is a theorized phenomenon in organosilicon compounds, in which hyperconjugation stabilizes or destabilizes certain accumulations of positive charge.   The phenomenon explains corresponding peculiarities in the stereochemistry and rate of hydrolysis.  
Second-row elements generally stabilize adjacent carbanions more effectively than their first-row congeners; conversely they destabilize adjacent carbocations, and these effects reverse one atom over.  For phosphorus and later elements, these phenomena are easily ascribed to the element's greater electronegativity than carbon.  However, Si has lower electronegativity than carbon, polarizing the electron density onto carbon.  
The continued presence of second-row type stability in certain organosilicon compounds is known as the silicon α and β effects, after the corresponding locants.  These stabilities occur because of a partial overlap between the C–Si σ orbital and the σ* antibonding orbital at the β position, lowering the S reaction transition state's energy.  This hyperconjugation requires an antiperiplanar relationship between the Si group and the leaving group to maximize orbital overlap.
Moreover, there is also another kind of silicon α effect, which is mainly about the hydrolysis on the silicon atom.