Darwin & Lie Detection
In the series ‘lie to me’, Dr. Lightman uses all kinds of microexpressions and body languages to detect lies. Well, this is not a fiction and it does happens in real life. So today, lets look at lie detection in real life!
(Note: this post is inspired by a paper written by Prof.Ekman, if you want to know more about lie detection then you should have a look at some of his researches!)
Darwin(1872)’s take on facial expressions & emotion
Remember the guy who constantly reminding us that we are not that much different from a chimpanzee, just a few millions years away? As it turns out, he was also the father of lie detection! Well, sort of. Darwin(1872) was the first scientific study of emotions which reveals the universality of emotions across species and the potential links between emotions and expressions. However, one failure of this his endeavour to understand emotion is the lack of consideration to when, how and why emotional expression are reliable or misleading.
Specifically, his book did not mention the situations where emotions do not reflect emotional states such as when we lie. The closest argument he made in relation to deception was when he suggested that some muscles are difficult to voluntarily control thus could potentially be used to mask expressions in order to hide true feelings. Lets say if you want to hide the fact that you are angry with your husband in the heat of an argument about who should do the dishes. Although you try really hard to suppress those muscles around your hand to not throw a punch, still your eyebrows come together, your eyes glare and your lips become narrow and thin. It doesn’t take an expert to know that your husband is about to be punished!
Darwin’s Hypothesis 1: Involuntary control -> detecting lies?
This scenario actually illustrates two interesting ideas. Firstly is the idea that if an expression can not be voluntarily made(e.g. glaring eyes), then you will not be able to inhibit it which is called the ‘Inhibition Hypothesis’. To understand this, you need to know that facial nucleus, a collection of motor neurons in the faces that are responsible for transmitting impulses to specific muscles to make them contract or relax, receive impulses from various parts of the brain. While the motor cortex underlines the ‘voluntary’ control of impulses to make a facial expressions , lower areas of the brain are responsible for the ‘involuntary’ control of certain emotions.
Behaviourally speaking, however, we don’t really need to locate the exact neural substrate in order to test Darwin’s idea. If Darwin is correct then facial actions that can not be voluntarily controlled should provide leakage of felt emotions that revels the true feelings. Indeed, Ekman and his collegues showed over and over again our poor ability to control the activities of certain muscles which I have listed below
Darwin’s Hypothesis 2: Lie detection: Face > Body?
The second idea of Darwin’s paper that’s illustrated in our ‘angry wife’ scenario is that it is easier to inhibit body movements than facial expressions when we lie which is called the ‘face> body leakage hypothesis’. Empirical evidence, however, does not seem to support this idea as much as the last one. Although we might be able to control our body better, we don’t normally have the intention to do so because we don’t often get a feedback from others for our body movements like we do for our facial expressions. For example,your mom might says “you are frowning too much, is everything ok?” but I would seriously doubt the likelihood of her saying “I know you don’t want to spend time with me because your feet always pointing to the door!”. As a result of this lack of feedback, we don’t normally pay attention to our body movements when we lie which goes against with Darwin’s idea where it is actually easier rather than harder to detect lies from the body than the face! Indeed, when participants were asked to detect lies from the body or the face of people with either fake or genuine happiness, more accurate judgements were made for watching body rather than facial movements. In addition, most actors stated after the experiment that they need to manage their facial expressions and few mentioned about body movements when they were asked how did they lie(Ekman & Friesen,1974).
Does it means that faces are unimportant for lie detection since we can mask our facial expressions anyway? Well, as most things in life, its complicated. Studies showed that when people are trained to identify microexpressions, their accuracy of lie detection become 80% and higher! So it seems that there are two level of facial expressions, namely micro and macro expression. Although macro expression is very misleading, microexpressions are dead giveaways to our true emotions that can transform you into a human lie detector like Dr. Cal Lightman!
Signs for lying
To understand how this works, we need to know all the players involved in the process of lying. In terms of body movements, we tend to shrug and/or speak with a high pitch when we lie.
In terms of microexpressions, masking smiles is the most robust sign of lying (i.e., superimposed smile over muscle movement; AU12 in FACS scoring) which tends to reflect the emotion of fear,sadnesss or disgust. Remember the Duchenne smile we have discussed yesterday? Yes, the differences lie on the pars lateralis part of the orbicularis oculi muscle, that is your lower eyebrow region(i.e., the region above ‘retractor anguli oculi lateralis’ in the picture below, AU6+12)
Indeed, studies showed that people find it very difficult to control the movement of pars latealis and is often manifested while watching amusing films rather than violent ones. Thus indicates that Duchenne smile is a sign of genuine happiness rather than masked ones to hide negative emotions!
(This picture was actually included in Darwin’s book and (A) is induced smile while (B) is real one)
Perhaps surprisingly, however, recent lie detection studies ignored this distinction between Duchenne smile and other smiles, for example, fridlund and colleagues found no relationships between smiling & self-reported happiness. But if you look closer, the measure he took was the amount of total smiles rather than the amount of ‘Duchenne’ smiles which is not a valid cue for lying! Therefore, when the experiment was repeated by Prof. Ekman, Duchenne smiles were found to be consistently correlated with happiness ratings! This correlation was found to be consistent in various studies such as those carried out on infants and fMRI studies. For instance, an EEG study showed that the cerebral activity that’s found in positive affect only activated when adults showed Duchenne smiles. To exclude the possibility of this activation reflects smile in general, further studies carried out on participants who can voluntarily control the pars lateralis part of orbicularis oculi and found the activation of positive-affect-related cerebral activity occurred ‘only’ when they made a Duchenne smile(Ekman & Davidson,1973).
Duchenne Smile in real life lie detection
So now we know that Duchenne smile is important for lie detection, however, just because this sign works does not mean we can use them. As microexpressions are extremely fast where Duchenne smile lasts around ½ to 4s, the question becomes whether we are able to see the differences of fake and Duchenne smile in real time. In a study carried out by Frank et al(1993), the accuracy was around chance level(56%) when the observer saw each smile separately which however increased significantly(around 74%) when they saw both smiles and able to compare them!Therefore, it seems that if we can manage to familiarise ourselves with Duchenne smile in order to be used as a criteria for evaluating the smile we see on others then it can be potentially used to detect lies in real life!
Interestingly, Duchenne smile doesn’t even require attention to make an impact on our emotion. For example, Frank et al(1993) showed that when asking participants about the overall impression of a person, the ratings become significantly more positive when they saw segments of Duchenne smile as compared to segments of non-Duchenne smile. This illustrates firstly we don’t need to focus on smile per se to be influenced and secondly Duchenne smile have a much wider impact on our social interaction such as forming impressions than simply being a lie detector. So Maybe next time you want to fake a smile in a party, think twice…it runs deep.
Asymmetry & Smooth expression
Spontaneous expression is more symmetrical than those deliberate ones. For example, studies showed more symmetrical smile in felt emotion among children than faked ones which is consistent with adults where symmetry of smile was nearly 96% for positive emotion and 75% for negative ones. In addition, spontaneous expression is also smoother where the deliberate expression tend to have elongated apex with shortened offset that looks rather artificial.
Overall, Darwin is right to say involuntary control is a giveaway to our true emotion, however, it is very reductive to say the face is more important than the body for lie detection simply because body movements are easier to be controlled than facial expressions. As it turns out, body movements are actually harder to inhibit due to the lack of intention and therefore are more helpful for detecting lies than your facial expressions! Nonetheless, microexpression is an exception which is so far the most accurate way to spot lies in real life once you have learnt to identify them, for example, based on their symmetry and smoothness.
So if you want to be a human lie detector, then microexpression and body language are ways to go! As always, thank you for reading and have a good day!This is my wordpress blog, feel free to drop by!https://michelleyan0625.wordpress.com
