CASME II: An Improved Spontaneous Micro-Expression
Database and the Baseline Evaluation
Wen-Jing Yan
1,2
, Xiaobai Li
3
, Su-Jing Wang
1
, Guoying Zhao
3
, Yong-Jin Liu
4
, Yu-Hsin Chen
1,2
,
Xiaolan Fu
1
*
1 State Key Laboratory of Brain and Cognitive Science, Institute of Psychology, Chinese Academy of Sciences, Beijing, China, 2 University of Chi nese Academy of Sciences,
Beijing, China, 3 Center for Machine Vision Research, Department of Computer Science and Engineering, University of Oulu, Oulu, Finland, 4 TNList, Department of
Computer Science and Technology, Tsinghua University, Beijing, China
Abstract
A robust automatic micro-expression recognition system would have broad applications in national safety, police
interrogation, and clinical diagnosis. Developing such a system requires high quality databases with sufficient training
samples which are currently not available. We reviewed the previously developed micro-expression databases and built an
improved one (CASME II), with higher temporal resolution (200 fps) and spatial resolution (about 2806340 pixels on facial
area). We elicited participants’ facial expressions in a well-controlled laboratory environment and proper illumination (such
as removing light flickering). Among nearly 3000 facial movements, 247 micro-expressions were selected for the database
with action units (AUs) and emotions labeled. For baseline evaluation, LBP-TOP and SVM were employed respectively for
feature extraction and classifier with the leave-one-subject-out cross-validation method. The best performance is 63.41% for
5-class classification.
Citation: Yan W-J, Li X, Wang S-J, Zhao G, Liu Y-J, et al. (2014) CASME II: An Improved Spontaneous Micro-Expression Database and the Baseline Evaluation. PLoS
ONE 9(1): e86041. doi:10.1371/journal.pone.0086041
Editor: Kun Guo, University of Lincoln, United Kingdom
Received September 11, 2013; Accepted December 4, 2013; Published January 27, 2014
Copyright: ß 2014 Yan et al. This is an open-access article distributed under the terms of the Creative Comm ons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work is partly supported by the National Natural Science Foundation of China (61075042, 61322206, 61375009, 61379095); 973 Program
(2011CB302201), China Postdoctoral Science Foundation (2012M580428); NCET-11-0273; GZ and XL were supported by Academy of Finland and Infotech Oulu.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: fuxl@psych.ac.cn
Introduction
A micro-expression is a brief facial movement which reveals a
genuine emotion that a person tries to conceal [1–3]. In addition,
micro-expressions might be unaware and/or uncontrollable to the
actor, thus may provide effective clues for detecting lies.
Therefore, micro-expression recognition has many potential
applications such as clinical diagnosis and interrogation. In the
clinical field, micro-expressions may be used for understanding
genuine emotions of the patients and promoting better therapies.
For instance, Ekman [4] analyzed an interview video of a patient
stricken with depression and that patient displayed a desperate
micro-expression which could predict a commit suicide. During an
interrogation or interview, micro-expression discloses what the
interviewee really feels and thus helps further investigation. For
instance, a micro-expression of scorn from Kato Kaolin’s
testimony in the O.J. Simpson trial betrayed his genuine feelings
[5].
A micro-expression is featured by its short duration. The
generally accepted upper limit of the duration is 1/2 s [3,6]. These
fleeting facial expressions, as observed, are usually low in intensity
– it might be so brief for the facial muscles to become fully-
stretched with suppression. Because of the short duration and low
intensity, it is usually imperceptible or neglected by the naked eyes
[1]. To better analyze micro-expressions and to help reveal
people’s feelings, an automatic micro-expression recognition
system is in great need.
Automatic facial expression recognition is booming. Research-
ers had developed many algorithms and the accuracy has reached
over 90% for the posed six basic facial expressions (anger, disgust,
fear, happiness, sadness and surprise). On the contrary, studies on
automatic micro-expression recognition have just started recently
and only several pieces of work were available. Shreve et al. [7]
divided the face into sub-regions (mouth, cheeks, forehead, and
eyes) and calculated the facial strain of each sub-region. The strain
pattern in each sub-region is then analyzed to detect micro-
expression from the video clips. Pfister et al. [8] proposed a
framework using temporal interpolation model and multiple
kernel learning to recognize micro-expressions. Polikovsky et al.
[9] used a 3D-gradient descriptor for micro-expression recogni-
tion. Wu et al. [10] developed an automatic micro-expression
recognition system by employing Gabor features and using
GentleSVM as the classifier. Wang et al. [11] treated a gray-
scale micro-expression video clip as a 3rd-order tensor and utilized
Discriminant Tensor Subspace Analysis (DTSA) and Extreme
Learning Machine (ELM) to recognize micro-expressions. Ruiz-
Hernandez and Pietika¨inen [12] proposed to encode the Local
Binary Patterns (LBP) using a re-parametrization of the second
local order Gaussian jet to generate more robust and reliable
histograms for micro-expression representation.
The success in conventional facial expression recognition largely
rely on sufficient facial expression databases, such as the popularly
used CK+[13], MUG [14], MMI [15], JAFFE [16], Multi-PIE
[17], and also several 3-D facial expression databases [18,19]. In
PLOS ONE | www.plosone.org 1 January 2014 | Volume 9 | Issue 1 | e86041