How does MethodHandles.Lookup.findSpecial(Class?> refc, String name, MethodType type, Class?> specialCaller) work? like invokespecial

Please see the code

public class TestMethodHandle {

    class G {
        void thinking(){
            System.out.println("im G");
        }
    }

    class F extends G {
        @Override
        void thinking(){
            System.out.println("im F");
        }
    }

    class S extends F {
        @Override
        void thinking(){

            MethodType methodType = MethodType.methodType(void.class);
            try {
                Field impl_lookup = MethodHandles.Lookup.class.getDeclaredField("IMPL_LOOKUP");
                impl_lookup.setAccessible(true);
                MethodHandles.Lookup IMPL_LOOKUP = (MethodHandles.Lookup)impl_lookup.get(null);
                MethodHandle mh = IMPL_LOOKUP.findSpecial(G.class , "thinking", methodType, G.class);//Please note here
                mh.invoke(this);
            } catch (Throwable throwable) {
                throwable.printStackTrace();
            }

        }
    }

    public static void main(String[] args) {
        new TestMethodHandle().new S().thinking();
    }

} 

Run it

im G

If I change the code：

MethodHandle mh = IMPL_LOOKUP.findSpecial(G.class , "thinking", methodType, F.class);
// im G

or

MethodHandle mh = IMPL_LOOKUP.findSpecial(G.class , "thinking", methodType, S.class);
// im F

or

MethodHandle mh = IMPL_LOOKUP.findSpecial(F.class , "thinking", methodType, S.class);
// im F

I know it has the same effect as invokespecial, How does it implemented?