These perceptual qualities also have additional hedonic
consequences of their own — sweet smelling odours are
pleasant and this quality may in itself motivate consumption
even if we cannot identify the actual odour or its
source. There is even evidence suggesting that such
odours activate the same reward pathways as tasted
sweetness . Conversely, bitter or sour smelling
odours — those previously paired with these taste qualities
— are likely to be rejected, especially if we cannot
recognize the odour. These perceptual changesto odours
may help compensate for the fact that odour, and food,
identification is particularly difficult even for common
foods .