The term "image quality" is often used to describe the performance of an imaging system. Recent research showed however that image quality may not be the most appropriate term to capture the evaluative processes associated with experiencing three-dimensional (3D) images. The added value of depth in 3D images is clearly recognized when viewers judge image quality of unimpaired 3D images against their two-dimensional (2D) counterparts. However, when viewers are asked to rate image quality of impaired 2D and 3D images, the image quality results for both 2D and 3D images are mainly determined by the introduced artifacts, and the addition of depth in the 3D images is hardly accounted for. In this article we describe an experiment where we applied and tested two alternative evaluative concepts: naturalness and viewing experience. It was hypothesized that these concepts would be more sensitive to the added value of depth in 3D images. Four scenes were used, varying in dimension (2D and 3D) and noise level (six levels of white Gaussian noise). Results showed that both viewing experience and naturalness were rated higher in 3D than in 2D when the same noise level was applied. Thus, the added value of depth is clearly demonstrated when the concepts of viewing experience and naturalness are being evaluated in contrast to earlier results found using image quality. The added value of 3D over 2D, expressed in noise level, was 2 dB for viewing experience and 4 dB for naturalness, indicating that naturalness appears the more sensitive evaluative concept for demonstrating the psychological impact of 3D displays.