|Semantics of line drawings|
The emotional effect of line shape is
probably partly due to cross-sensory
associations such as the bouba/kiki effect:
Which is "Bouba" and which is "Kiki"?
"The bouba/kiki effect is a non-arbitrary mapping between speech sounds and the visual shape of objects. This effect was first observed by German-American psychologist Wolfgang Köhler in 1929. In psychological experiments, first conducted on the island of Tenerife (in which the primary language is Spanish), Köhler showed forms similar to those shown at the right and asked participants which shape was called "takete" and which was called "baluba" ("maluma" in the 1947 version). Although not explicitly stated, Köhler implies that there was a strong preference to pair the jagged shape with "takete" and the rounded shape with "baluba".From Wikipedia.
In 2001, Vilayanur S. Ramachandran and Edward Hubbard repeated Köhler's experiment using the words "kiki" and "bouba" and asked American college undergraduates and Tamil speakers in India "Which of these shapes is bouba and which is kiki?" In both groups, 95% to 98% selected the curvy shape as "bouba" and the jagged one as "kiki"."