When light reflects in a concentrated manner off of a surface, a specular highlight results. Specular highlights can be thought of as “pseudo” reflections of bright areas in the scene (sunlight, bright lights, and so on). Modifying the specular attributes affects the perceived reflectivity for a surface. When you reduce the specularity, you in turn reduce the perceived reflectivity.
Changes to this attribute do not alter the surface in the scene view, so you need to check the Material Sample in the Attribute Editor (see the following illustration). You can also render a test image ().
As you work with shading, you’ll find many attributes that have no effect in the scene view, for instance, Ambient Color and Translucence. Generally, the scene view is a rough approximation of how the scene will render.