A Comparison of Effects on Heart Rate & Brain Activity of Allowing Plain Chocolate to Melt in the Mouth and Kissing a Familiar Partner
An experiment made by Bridger, D., Gandhi, K., Gill, S. & Lewis, D.
Changes in heart rate and brain activity (EEG) were monitored in six heterosexual couples, in an established relationship, to compare the effects on brain and body of two forms of oral and olfactory stimulation – kissing and allowing chocolate to melt in the mouth.
Each person was given a bar of plain chocolate (Deeply Dark from Cadbury Bourneville) and asked to break off a piece and allow it to slowly melt in their mouth. They were requested not to chew or bite the chocolate but merely to wait until it started to melt and, at this point, to signal, non-verbally, this had occurred. The couple was then instructed to kiss in the way they would normally.
It was found that, so far as both heart rate increase and brain wave amplitude are concerned, the effects of chocolate exceed those of a kiss. Specifically, the main area of increased brain activity occurred in the ‘alpha frequency band’ (8 – 14Hz) a type of brain wave typically associated with a subjective feeling of relaxed alertness and what is generally considered a pleasant and enjoyable state of mind. An analysis of the EEG data showed significant increases in amplitude in the alpha band at the moment the chocolate melted. The maximum power (amplitude) at the moment of chocolate melt increased from an average of 2.3 µV at baseline to 4.3 µV.
An analysis of heart rate data showed a similar increase for both the kissing and the chocolate eating condition (see Figure 1).
Figure 1: Heart rate in beats per minute (bpm) for the different conditions.
Chocolate produced not only a larger increase in heart rate than kissing did, but also a more sustained one. Figure 2 gives the heart-rate graph for one couple.
Figure 2: Heart-rate variation over 8 minutes of the experiment. The red line is the female participant, the blue line the male one.
The 22-year-old male’s heart rate increased significantly, from around 60 bpm at rest to 90 bpm while kissing. The 24-year-old female appeared to be less affected by the kiss with her heart rate rising by only around 10 bpm. She was, however, more greatly affected by the chocolate, as reflected by a heart rate increase of some 20 bpm soon after placing a piece in her mouth. Her overall peak at the melt moment was less than that of the male, peaking at around 90 bpm. While, in the man’s case, this maximum increase was fairly short-lived after the dip it, then rose again to finish about a minute after the melt moment around 12 bpm higher than at rest. Where the female was concerned heart rate continued to rise from the moment she placed the chocolate in her mouth, during the melt moment.
Despite the short half-life of the main stimulant within chocolate, phenylethylamine, this product does appear to exert a strong psychoactive effect, which may well be linked to increased levels of alertness. When first introduced to the UK during the 15th century chocolate was seen as a medication and used to treat a wide range of conditions, especially fatigue and depression as well as, more bizarrely, gout and kidney stones! The common perception that chocolate lifts mood when one is feeling down does therefore find support in this (as well as in other) studies. However, one must also factor in the strong associations of chocolate consumption with happy events in life and these positive emotions are also likely to play some role in the effects found here.
Probably the team is searching for new participants!
Bridger, D., Gandhi, K., Gill, S. & Lewis, D.
The Mindlab.org
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