At the University of Kansas art museum, scientists tested the effect of different colored walls on two groups of visitors to an exhibit of paintings. For the first group the room was painted white: for the second, dark brown. Movement of each group was followed by an electrical equipment under the carpet. The experiment showed that those who entered the dark brown room walked more quickly, covered more area, and spent less time in the room than people in the white one. Dark brown made people more active, but the activity ended sooner. Not only the choice of colors but also thegeneral appearanceof a room affects those inside. Another experiment presented people with photographs of faces whose energy was to be commented. Three groups of people were used: each was shown the same photos, but each group was in an ordinary room—a nice office. The third was in a tastefully designed living room with carpeting. Results showed that the people in the beautiful room tend to give higher marks to the faces than those in the ugly room did. Other studies suggest that students do better on tests taken in comfortable rooms than in ordinary-looking or ugly ones.

Which of the following is the best expression of the main idea of this passage?