The 2PD tests sites were the extraoral surface of the lip (approximately half way between philtrum and oral commissure) and the dorsum of the tongue opposing the second premolar. For TDT, the mucosa of the cheek opposing the second premolar and on the linea alba was used as additional test site. Whereas these test sites were evaluated on both sides, the 2PD test was additionally applied to the tip of the tongue without side discrimination. For one particular analysis all TDT readings per participant were averaged (TDT.global).