Figure 2 - 'Smiley' faces series ranging from glumness to happy

From the following article

Visual/verbal analogue scales: Examples of brief assessment methods to aid management of child and adult patients in clinical practice

H R Chapman & N Kirby-Turner

British Dental Journal 193, 447 - 450 (2002) Published online: 26 October 2002

doi:10.1038/sj.bdj.4801593