Introduction

The aim of the current article is to establish a connection between the effects of olfactory stimuli on information processing and research on priming. In addition, guidelines with regard to how odors can be used to prime people are described.

Priming in the social sciences

Priming involves stimuli that are influencing higher-order cognitive and behavioral processes although the individual is not aware of this being the case. Higher mental processes refers to judgement and social behavior. Environmental stimuli can prime (influence) behavior, for instance perceiving a stimulus can influence your behavior. Four different types of priming are described by Loersch and Payne (2011):

Semantic priming (looking for categories)

Construal priming (judgement)

Behavior priming (action)

Goal priming(motivation)

Which type occurs is dependent on the situation one is in, therefore, the different priming types can all have different effects depending on the situation and personal characteristics. Next to these categories, priming can be divided into”

Perceptual priming (when the perceptional characteristics of the prime and the target are equal, this is not the same as semantic priming).

Repetition priming (quicker processing of stimuli that have been presented multiple times. The stimulus becomes the prime)

Affective priming (when there is an unintentional influence of a first affective response, which acts as a prime, on the processing of a target stimulus).

The ideo-motor action principle, developed by William James, states that if a cognitive representation becomes activated, the likelihood that an action will follow increases. Spreading of activation (nodes in memory activate each other), can also lead to priming. This all happens without taking effort and involuntarily. In cognitive psychology, the lack of awareness is seen in light of the capacity to perceive a presented stimulus whereas in social psychology, it is about being unaware of the influence that stimuli can have, regardless of whether one is able to see the stimulus or not. Being influenced without being aware of it is called subliminal priming whereas being aware of it is called supraliminal. Both types have been found to be effective.

Properties of olfaction

Odorants are the chemical substances that can cause the experience of an odor, thus, the odor is only an experience. Odor objects are odors stored in memory, they consist of one perceptual event but can be elicited by different odorants. Odorants are less frequently noticed by people than those of other sensory systems. This can be caused by the fact that the source of odorants are more difficult to recognize. Odors are also perceived differently depending on the attentiveness level. People adapt easily to odors but although you do not notice the odor anymore, it can still have an effect. Given that priming works best if one is unaware of it and that odors are adapted to quickly, they are very appropriate to use in priming. Odors can also trigger emotions which makes them interesting for affective primes. People have difficulties naming odors, therefore, odor object identification is vulnerable to ambiguity. This has consequences for the priming because it will be harder to establish a clear link between an odor and a target.

The most important dimension of odors is their valence, which can range from unpleasant to pleasant. Other dimensions are intensity, edibility and familiarity which, from an evolutionary perspective, can lead to approach or avoidance behavior. A relevant question is whether priming with odors is different from priming with visual stimulation.

Motivation priming

Odors are as well-functioning as visual stimuli in preventing us from running into environmental hazard. Because the link between stimuli and action is very clear in these situations, it can be argued that this does not count as priming. Odors can also be goal primes. For example, food odors can cause people to start eating which is used in the supermarket where it smells of freshly baked bread. In a study in France, presenting odor of melon led to people choosing melon as starter more often whereas pear, often eaten as dessert, led to more fruit desserts chosen. This shows that odors can result in goal priming but in different ways.

Semantic and construal priming

It is the question whether the odor of camembert cheese primes words related to other French foods (or maybe cheeses) or also to a French sport event (Tour de France). From a semantic perspective, the camembert odor might function as a prime for French food or cheese, however people might not be able to identify the smell as being French or being cheese. It is dependent on the interpretation which effects will be elicited and also the valence can vary according to interpretation. Therefore, from a valence perspective, the camembert can lead to affective responses because one can like or dislike the smell leading to increased accessibility of other liked or disliked products. The word camembert is expected to evoke a shorter reaction time when other French words are presented, measured with a Lexical Decision Task. The priming can also be based on autobiographical memory. Camembert might activate concepts as being on holiday in France. Another priming route is based on mood which means that mood at time of a judgement is used in making a judgement. Odors can also function as mood enhancers that subsequently lead to certain behaviors that are associated with a particular mood state. Odors are problematic in semantic priming but can be explained by alternative routes such as memory.

Applications of odor priming

It can be concluded that odors can lead to behavioral and goal primes because of their valence. Odors can be good affective primes because they are evaluated mainly in terms of good or bad. Based on how they are being evaluated, odors can lead to approach or avoidance behavior. This is already used in, among others, stores, at the workplace and in health care settings. However, odors can only called primes if people stay unaware of their influence, therefore it is better to use only small amounts of odor. Specific priming is possible with semantic priming but not if odors are used because it is difficult to know how an odor is being categorized by the individual. It is better if odors fit a category that is common and a prototype for the category. A study in which semantic olfactory priming was shown has been conducted by Holland et al. (2005). In this study a citrus odor led to increased cleaning behavior because of the activation of a cleaning concept. In another study of Dijksterhuis et al. (2013) subjects were presented with 3 different odors (2 pleasant and 1 unpleasant) that were not noticed. Cleaning actions were counted and in the unpleasant condition, less cleaning was recorded. This study shows that, in addition to semantic priming, other priming types are of influence. Namely, the affective value of the odor might explain the difference in cleaning. Being able to name an odor interferes with the implicit priming effects, probably because spreading of activation is different because of cognitive input.

Priming with odor via memory can lead to consumers buying more goods, however, memories are personal so the effects on buying behavior can vary a lot. The focus can be on odors linked to pleasant experiences, to enhance a product’s attractiveness (odor of sunscreen is associated with holidays). The focus can also be on the relation between an odor and an experience. This has been studied with subjects doing tasks in a room where an odor was spread. Subsequently, different odors were presented and the most appropriate one for the room had to be chosen by the subjects who did not explicitly recognize the odors.

Multi-modal priming

Laboratory settings can interfere if an association between an odor and a concept has to be established. Subjects often report that they smell computers or rubber. A solution would be to establish cross-modality correspondences using combinations of olfactive stimuli and stimuli of other modalities, such as pictures. Another option is to create an appropriate context, for instance with pictures, in addition to the odor. By doing so, the odor will be more likely to work as semantic prime than affective prime. Degel and Koster (1998) describe recommendations for effective odor priming:

The test does not supply explicit information about stimuli.

The test acknowledges the nonverbal character of odor perception and memory

The test allows perception of odors in a situation which is for the most part a biotic, normal everyday situation (this is why priming in laboratories is often ineffective).

Priming is a promising concept, especially olfactory priming, nevertheless, a lot of future research has to be conducted in order to get to know how priming has to be applied accurately.