High-fidelity rendering of complex scenes at interactive rates is one of the primary goals of computer graphics. Since high-fidelity rendering is computationally expensive, perceptual strategies such as visual attention have been explored to achieve this goal. Inattentional Blindness (IB) experiments have shown that observers conducting a task can fail to see an object, although it is located within the foveal region (2a?|). However, previous attention based algorithms assumed that IB would be restricted to the area outside the foveal region, selectively rendering the areas around task-related objects in high quality and the surrounding areas in lower quality. This paper describes a psychophysical forced-choice preference experiment assessing if participants, performing a task or free-viewing animations, would fail to notice rendering quality degradation within the foveal region. The effect of prior knowledge on the level of perceived quality is also studied. The study involves 64 participants in four conditions: performing a task, or free-viewing a scene, while being naive or informed about assessing rendering quality. Our results show that participants fail to notice the additional reduction in quality, decreasing the overall computation 13 times. There was also a significant difference in the results if free-viewing participants were informed.