Olfactory Cues Modulate Facial Attractiveness

Demattè, Österbauer, & Spence

Hummmm?

Sexy smellProtective smellSmell of attraction

Background Facial attractiveness-Visual

• Facial symmetry

• How much a face conforms to an average prototypeLanglois

Symmetry

average

averager

averagest

Background

Attractiveness is not just dependent on the vision but is often adjusted by other sensory cues• Voices have been shown to influence a

person’s perceived attractiveness

Olfactory cues (smell) also play an important role in nonverbal communication • A significant positive correlation found

between the rated sexiness of a man’s body odor & his facial attractiveness to females

BackgroundOlfactory cues

• A man’s major histocompatibility complex will help decide how attractive his bodily odor is to females (They prefer those with a different MHC)Major histocompatibility complex - A set of

molecules displayed on cell surfaces that are connected to our immune system responses through recognition of "self" and "non-self"

• Woman’s preference for the scent of some males has been shown to change with her menstrual cycle

Smelly Boys

Aim

To investigate whether olfactory cues can influence people’s judgments of facial attractiveness

Hypothesis

A pleasant versus unpleasant odor can modulate female participants’ ratings of the perceived attractiveness of briefly presented male faces

Sample

16 female volunteers• The University of Oxford

• Age 20 to 34, M=24

• ‘Blind’ at beginning

• Completed a questionnaire ensure that they had a normal sense of smell, no history of olfactory dysfunction, & normal vision Chose women because previous research has

suggested that females may be more sensitive to the effects of olfactory cues than are males

MaterialsForty male faces for visual stimuli

• From a standardized database

• Extensively characterized for attractiveness & categorized into high, medium, & low attractiveness

• 20 faces from each of the high & low groups

Four odors (2 male & 2 non-male) & clean air • 2 pleasant odors: geranium & male cologne ‘‘Gravity”

• 2 unpleasant odors: male body odor & rubber

A custom-built computer-controlled olfactometer was used to deliver the odorants

Procedure/method

Laboratory experiment• Repeated measures design

Subject to order effects

IV= Pleasant odors, unpleasant odors, neutral odors

DV=Modulation of female participants’ ratings of the perceived attractiveness of male faces

Procedure/method

3 blocks of 40 random trials (each person completed 120 trials)• Each face was randomly presented 3 times

during each sessionOnce with a pleasant odorOnce with an unpleasant odorOnce with a neutral odor (i.e., clean air)

Procedure/method

Participant sat staring at a computer with their chins on a chin rest

They were told to look at a fixation mark on the screen They were to exhale through their nostrils when they

heard a quiet tone and inhale when they heard a louder tone and which point an odor was released

They had to indicate if an odor had been released or not using the keyboard

1 second later one of the faces appeared for ½ second in the center of the screen

As soon as the face disappeared the odor stopped and clean air was delivered.

The screen then turned black

Procedure/method

Then a 9-point rating scale appeared and the participants were to rate the perceived attractiveness of the face that they had just seen

1 (least attractive) to 9 (most attractive) • What is this called?

As soon as they made their rating, clean air was delivered and the next trial started

Procedure/method

At the end each participant was asked to smell the odors individually & to rate each odor on several different dimensions use a pen and paper Labeled Magnitude Scale (LMS) from 0-100. • odor intensity• odor pleasantness• odor familiarity

The order of presentation of the odors and the scales was randomized between participants

Labeled Magnitude Scale

What is the difference between this and a Likert Scale?

Between this and a forced choice?

Procedure/method

In order to counterbalance the presentation of each face/odor combination, the entire set of 40 faces was divided into 4 groups of 10 faces each (5 high attractiveness & 5 low attractiveness) with close to the same mean attractiveness. • Each group of faces was then presented

with 1 different possible combination of pleasant–unpleasant odors, counterbalanced across participants.

Procedure/method

So each participant rated 1.10 faces presented with clean air, the geranium

odor, & the body odor during the experiment.

2.10 faces with clean air, the male perfume, & the rubber odor

3.10 faces with clean air, geranium odor, & the rubber odor

4.10 faces clean air, the male perfume, & the body odor. The same odor was never presented to participants on

consecutive trials. The experiment lasted for approximately 50 min in total.

Results/Findings

The faces were found significantly less attractive when presented together with an unpleasant odor than when presented with either a pleasant odor or with the neutral clean air• Didn’t matter if the odor was body relevant

There was no significant difference between pleasant versus neutral clean air

Discussion

Adds to a growing list of studies demonstrating that the presence of olfactory cues can exert a small but significant cross-modal influence on people’s judgments of a variety of non-olfactory stimulus attributes/qualities (Smell matters)• Adds to previous evidence that shows that the

presence of fragrance cues can influence people’s evaluation of job applicants

• Would be interesting to see what happens under more ecologically valid conditions

Ethics

Ethical standards• 1964 Declaration of Helsinki

A set of ethical principles regarding human experimentation developed for the medical community by the World Medical Association (WMA)~ Widely regarded as the foundation of human research ethics

• Department of Experimental Psychology, University of Oxford

Evaluation

Strengths• Controlled

• Counterbalanced to control for order effects

• Replicable

Weaknesses• Generalization (population/sample)

• Demand characteristics

• Halo dumping

• Validity (ecological, construct)

Evaluation

Construct validity? Yes• A link could be established between the face & the

smell because the technique used presented them as a single stimulus & cross-modal (perceptions involving 2 senses) interactions were checked

• Presentations of the odors were brief so the influence of the odors on mood didn’t interfere with face preferences

• Trials were randomized so the effects could be attributed to the smells, not order effects (practice or fatigue)

Evaluation

Construct validity? No• The unpleasant smells may

have distracted the participants’ attention causing them to find the faces less attractive rather than affecting perception of the face

• The participants might have been halo dumping

EvaluationWere the effects due to a halo-dumping?

• Can occur whenever the appropriate response alternative for a relevant attribute is unavailable to participants. This can lead participants to ‘dump’ the values for a relevant attribute that is not available in the range of alternative response scales providedSo they describe a smell as sweet when it is

really vanillaIn this case they might have been expressing

their like or dislike of the odor on the attractiveness scale

• Possible as they only had one scale to use, so couldn’t separate their evaluations

Evaluation

Demattè et al say no• the participants in the study had to perform

an odor detection task at the beginning of each trial, meaning that odor and visual information were responded to as 2 distinct and individuated

• ‘‘Attractiveness’’ is a clear, natural, & easy characteristic to consider when rating human faces, so it is unlikely that the participants had doubts concerning which variable they were supposed to rate in the task

Vocabulary

counterbalancecross-modelfacial attractiveness halo-dumpingLabeled Magnitude Scalemajor histocompatibility complexolfaction olfactory cuesorder effectspilotrepeated measures design

Resources

Demattè, M.L., Österbauer, R. and Spence, C. (2007), Olfactory cues modulate facial attractiveness. Chemical Senses. 32(6). pp. 603–610

http://www.cehs.siu.edu/fix/medmicro/mhc.htm