Valid:
• a link could be established between the face and the smell because the technique used presented them as a unitary stimulus and cross-modal interactions were checked
• by making presentations of the odours brief they avoided any influence on the odours on mood interfering with face preferences
• trials were randomized (and successive presentation of one odour avoided) so the effects could be attributed to the smells, not practice or fatigue effects

Not valid:
• the unpleasant smells may have distracted the participants’ attention causing them to find the faces less attractive rather than affecting perception per se.
• the participants might have been halo dumpling i.e. expressing their like or dislike of the odour on the attractiveness scale
• this is possible as they only had one scale to use, so couldn’t separate their evaluations

Though this is unlikely as:
• halo dumping mainly occurs with flavour perception where smell and taste are both important
• smell and vision are not confused in the same way
• the odour was detected at the beginning of the trail, attractiveness was rated at the end
• attractiveness is an unambiguous characteristic of human faces

Physiological: Paper 2 Questions