Aussiepax - it might be relatively easy to notice a turn in daytime when light levels and shadows in the cabin change in response to a turn (or you are sitting near a window) but it might not always be as detectable as many think. There's an excellent article on spatial disorientation in the current issue of Flight Safety Australia called 'Don't believe your ears". It also features Captain de Crespigny in an interesting experiment with a Barany chair and gives the methodology so anyone who's interested can replicate these somatogyral/somatogravic illusionary experiments with their own rotating chair at home. The author states that even the graveyard spiral isn't detectable to the inner ear - a pilot can still sense they are in straight and level flight. From the story... "One telling detail in how the vestibular apparatus functions is that the semi-circular canals have a stimulation threshold of two degrees a second. You will not feel yaws or rotations slower than this. Autopilot software on airliners exploits this fact; so that passengers are unaware an aircraft is zig-zagging to avoid storms or traffic. But the threshold also means pilots can't detect a slow divergence from straight-and-level flight."
Full article here:
Civil Aviation Safety Authority - FSA issue 97 - Don't believe your ears