In a physically based renderer such as Arnold, what material attribute controls reflectivity according the angle of the surface to the camera? For example, if you want to make the front-facing surface more reflective relative to the side-facing surface, what should you increase?

Autodesk Maya, commonly shortened to just Maya, is a 3D computer graphics application that runs on Windows, macOS and Linux, originally developed by Alias and currently owned and developed by Autodesk. It is used to create assets for interactive 3D applications, animated films, TV series, and visual effects.
Blender and Maya are two of the most popular 3D software applications on the market today.