Comparison of micro-expressions and lie detectors in term of accuracy

Nowadays, more and more criminal comedies use the idea of body language to help police to solve the case. Moreover, as the new component of body language, micro-expression has been used in some famous American comedy and lie to me is one example. On the other hand, lie has always been an interesting topic through history. In 1977, a University of Southern California social psychologists’ study claimed that people lied 200 times per day.(1) Lies can divide into two types: malicious falsehood and white lie (harmless untruth). In spite of the numerous amounts of lies, research estimates that over 75% of all lies are undetected. Researchers keep studying and trying various ways to detect lie in term of accuracy. The most accuracy two has been founded are micro-expression and lie detector. (2)

Micro-expression is a brief involuntary facial expression shown on the face of humans. It is a momentary involuntary facial expression that people unconsciously display when they are hiding an emotion. Haggard and Isaacs first discovered Micro-expressions in the 1960s. In addition, Micro-expression is also one of the most efficient body language that can test whether people lie or not. Not as regular facial expressions, it is difficult to hide micro-expression reactions because it is uncontrollable. Micro means mini, if you have a close-up view of people’s expression or action, you can discover that different micro-expression represent different information.

The lie detector has another technical term, which is polygraph, it was invented in 1921 by John Augustus Larson, a medical student at the University of California at Berkeley and a police officer of the Berkeley Police Department in Berkeley, California. (3) Lie detector is the practice of attempting to determine whether someone is lying. It measures and records several physiological directories such as blood pressure, pulse, respiration, and skin conductivity while the subject is asked and answers a series of questions. When a person lies, is assumed that a trained expert can detect whether the person is lying through the physiological changes. The belief is that deceptive answers will produce physiological responses.

Recently, some people try to compare these two methods of testing lies. Some argue that lie detector is much more efficient and reliable to use, as machine is much more objective than human. However, I think that micro-expression is much more accurate in two ways: more specific, more flexible, and indistinguishable.

The role of micro-expression and polygraph

Micro-expressions can express the seven universal emotions: disgust, anger, fear, sadness, happiness, surprise and contempt. Disgust is characterized by the upper lip being raised, generally exposing the teeth, together with a wrinkling of the nose. Anger’s micro-expression is composed of the lips being narrowed and pressed together tightly. You will also see the eyebrows slanted down and towards the nose. In fear, you will see the lips horizontal stretched towards the ears. The lower eyelids will be tensed and the upper eyelids will be raised. In sadness, the upper eyelids and outer edges of eyebrows will droop. The subject will appear to have very little focus in their eyes. Also, the corners of the lips will be pulled slightly down. The characteristic of happiness is the smile. In true happiness you will see the corners of the lips turn up and the cheeks will rise slightly. But the key sign of true happiness is the crow’s-feet that appear at the corners of the eyes. If you don’t see movement from the muscles around the eyes or crows-feet, the smile will be a fake. Surprise can be recognized by widened eyes and raised eyebrows. Also the mouth will open a little bit. In a true expression of surprise, the eyebrows will be raised for less than a second. So if someone is acting surprised, but leaves their eyebrows lifted for more than a second, which means they are lying. It is the only micro-expression that is unilateral. The only one that is biased to one side of the face. (4) All other micro-expressions are equally distributed across the face about a vertical centerline. The Complete betrayal of contempt is the raising of one side of the lips. It can be very subtle and even look like just a twitch.

There are three basic approaches to the lie detector test: The Control Question Test (CQT), The Directed Lie Test (DLT) and The Guilty Knowledge Test (GKT). CQT is often used to determine whether certain criminal suspects should be prosecuted or classified as uninvolved in the crime. DLT tries to detect lying by comparing physiological responses when the subject is told to deliberately lie to responses when they tell the truth. Compared physiological responses with multiple-choice type questions about the crime, GKT choose to use the one contains information only the crime investigators and the criminal would know about. (5) 

The disadvantage of Lie Detector

Lie detector can test reality, it can measures and records several physiological directories, such as blood pressure, pluses. Nervousness, anger, sadness, embarrassment, and fear can all be causal factors in altering one’s heart rate, blood pressure or respiration rate. (6) However, there are a number of medical conditions such as colds, headaches, constipation, or neurological and muscular problems, which can also cause the physiological changes measured by the polygraph. Thus despite we can find out some emotion change and body symptoms, we can not know the reason which caused this result through the data of lie detector. However, using the micro-expression observation may help us notice the real truth instead of some appearance factors. Moreover, some data showed by lie detector may be useless by estimating the truth of the words. Thus some times we will waste a lot of on doing this kind of research. But micro-expression can easy be used through the interrogation. In other words they do not need to do extra research.

Micro-expression is more flexible

Comparing the micro-expression and lie detector in terms of accuracy, I think micro-expression is more accurate than lie detector because human is more flexible than machine and micro-expression can detect more specific than lie detector. By observing different micro-expression, people can make homologous estimation, as human makes machine. There must be some oversights and limitation. Furthermore, lie detector is confined to explore physiological reaction and it cannot test subtle reaction. (nuance of expression is a kind of inner reveal and hide) (see figure 12)

Figure 13-Micro-expression used in estimating lies


Lie detectors have more limitations than micro-expressions. When we use instrument polygraph, it must inform the person being tested and the participators should be agree with that to load test equipment on the body and to minimize unnecessary movement. It also needs to limited on time and space. However, according to the micro-expression, the person being tested does not need to load a device and restrictions on movement. In other words, the result shows of participators whether lie or not is depends on the detectors choice. For example, people who are testing by lie detector, they may fear that the machine will indicate they are lying when they are telling the truth and that they will be falsely accused of lying. (7) However, by Observing micro-expression, the subject may not know he or she has been tested.


Micro-expression is very useful in wide fields, especially on testing lie. It can be identifying from tinny actions, such as expression in one’s eye or simile. Lie detector measures and records several physiological indices. It is also very good for testing lie. Both of them are have many advantages, but micro-expression is more accurate and effective than lie detector because human is more flexible than machine. Although lie detector can test the real things, it cannot test the subtle reaction. Therefore, I think micro-expression is better to use to test lie than lie detector.

Word count: 1296

1 Neal Simon and Mario R. Ventreli, “How I learned to stop worrying about liars and love microexpressions,” American Journal of Family Law. 25.4 (Winter 2012): 143, accessed March 17, 2012.


3 “Polygraph/Lie Detector FAQs,” International League of Polygraph Examiners, accessed March 17, 2012, http://www.theilpe.com/faq_eng.html.

4 “How to Detect Micro Expressions,” Ehow, accessed March 17, 2012, http://www.ehow.com/how_5311172_detect-micro-expressions.html.

5 “polygraph (‘lie detector’), ” The Skeptic’s Dictionary, accessed March 17, 2012, http://www.skepdic.com/polygrap.html.




One comment on “Micro-expression

  1. The introduction section suggests to the reader what will be discussed, defines the two types of lie detection adequately and gives some relevant background information about both. There are times when some facts are uncited and wording is unclear and when not unclear, it’s obvious that sentences have been copied and pasted directly from the source text (i.e. plagiarised). The majority of the section “The role of micro-expression and polygraph” is copied and pasted from your e-how citation. I cannot grade your ability to write or develop an argument from this section at all.

    The section on flexibility is less problematic in terms of plagiarism, but developing argument is less supported and based more on what seems like a common-sense approach–unfortunately inadequate for this level of research. I’m left unsure of the accuracy of microexpressions as they are accounted for by human and human error. Unfortunately, with plagiarised sections and lack of supported evidence, the reader cannot distinguish your comprehension of the information nor its argument’s reliability.

    There is some inappropriate term usage (e.g. “nowadays”, etc.). Proofreading would beneficial to catch word form error (“term”), capitalisation (“lie to me”) and grammar slips. Keep subjective use out of academic essays.

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