Shape-invariant encoding of dynamic primate facial expressions in human perception

  1. Nick Taubert
  2. Michael Stettler
  3. Ramona Siebert
  4. Silvia Spadacenta
  5. Louisa Sting
  6. Peter Dicke
  7. Peter Thier
  8. Martin A Giese  Is a corresponding author
  1. Section for Computational Sensomotorics, Centre for Integrative Neuroscience & Hertie Institute for Clinical Brain Research, University Clinic Tübingen, Germany
  2. International Max Planck Research School for Intelligent Systems (IMPRS-IS), Germany
  3. Department of Cognitive Neurology, Hertie Institute for Clinical Brain Research, University of Tübingen, Germany
10 figures, 4 tables and 1 additional file

Figures

Stimulus generation and paradigm.

(A) Frame sequence of a monkey and a human facial expression. (B) Monkey motion capture with 43 reflecting facial markers. (C) Regularized face mesh, whose deformation is controlled by an embedded …

Raw data and statistical analysis.

(A) Histograms of the classification data for the four classes (see text) as functions of the style parameters e and s. Data is shown for the human avatar, front view, using the original …

Fitted discriminant functions Pi(e,s) for the original stimuli.

Classes correspond to the four prototype motions, as specified in Figure 1D (i = 1: human-angry, 2: human-fear, 3: monkey-threat, 4: monkey-fear). (A) Results for the stimuli generated using …

Tuning functions.

(A) Fitted species-tuning functions DH(s) (solid lines) and DM(s) (dashed lines) for the categorization of patterns as monkey vs. human expressions, separately for the two avatar types (human and …

Fitted discriminant functions Pi(e,s) for the condition with occlusions of the ears.

Classes correspond to the four prototype motions, as specified in Figure 1D (i = 1: human-angry, 2: human-fear, 3: monkey-threat, 4: monkey-fear). (A) Results for the stimuli generated using …

Equilibration of low-level expressive information.

(A) Mean perceived expressivity ratings for stimulus sets that were equilibrated using different types of measures for the amount of expressive low-level information: OF: optic flow computed with an …

Fitted discriminant functions Pi(e,s) for the experiment with equilibration of expressive information.

Classes correspond to the four prototype motions, as specified in Figure 1D (i = 1: human-angry, 2: human-fear, 3: monkey-threat, 4: monkey-fear). (A) Results for the stimuli set derived from …

Appendix 1—figure 1
Details of generation of the monkey head model.

(A) Irregular surface mesh resulting from the magnetic resonance scan of a monkey head. (B) Face mesh, the deformation of which is following control points specified by motion-captured markers. (C) …

Appendix 1—figure 2
Details of generation of the human head model.

(A) Human face mesh and deformations by a blendshape approach, in which face poses are driven by the 43 control points (top panel). Tension map algorithm computes compression (green) and stretching …

Appendix 1—figure 3
Motion morphing algorithm and additional results.

(A) Graphical model showing the generative model underlying our motion morphing technique. The hierarchical Bayesian model has three layers, reducing subsequently the dimensionality of the motion …

Tables

Key resources table
Reagent type
(species) or resource
DesignationSource or referenceIdentifiersAdditional information
Software, algorithmCustom-written software written in C#This studyhttps://hih-git.neurologie.uni-tuebingen.de/ntaubert/FacialExpressions (copy archived at swh:1:rev:6d041a0a0cc7055618f85891b85d76e0e7f80eedTaubert, 2021)
Software, algorithmC3DserverWebsitehttps://www.c3dserver.com
Software, algorithmVisual C++ Redistributable for Visual Studio 2012 Update4 × 86 and x64Websitehttps://www.microsoft.com/en-US/download/details.aspx?id=30679
Software, algorithmAssimpNetWebsitehttps://www.nuget.org/packages/AssimpNet
Software, algorithmAutodesk Maya 2018Websitehttps://www.autodesk.com/education/free-software/maya
Software, algorithmMATLAB 2019bWebsitehttps://www.mathworks.com/products/matlab.html
Software, algorithmPsychophysics toolbox 3.0.15Websitehttp://psychtoolbox.org/
Software, algorithmR 3.6Websitehttps://www.r-project.org/
OtherTraining data for interpolation algorithmThis studyhttps://hih-git.neurologie.uni-tuebingen.de/ntaubert/FacialExpressions/tree/master/Data/MonkeyHumanFaceExpression
OtherStimuli for experimentsThis studyhttps://hih-git.neurologie.uni-tuebingen.de/ntaubert/FacialExpressions/tree/master/Stimuli
Appendix 1—table 1
Model comparison.

Results of the accuracy and the Bayesian Information Criterion (BIC) for the different logistic multinomial regression models for the stimuli derived from the original motion (no occlusions) for the …

Model comparison
Monkey front viewModelAccuracy [%]Accuracy increase [%]BICParametersdfχ2p
Model 138.29748733
Model 257.8619,56 (relative to Model 1)50763632411<0,0001
Model 349.4911,2 (relative to Model 1)61253631362<0,0001
Model 477.5319,67 (relative to Model 2)35863931490<0,0001
Model 577.530 (relative to Model 4)359842311.997<0.0074
Model 677.42−0,11 (relative to Model 4)35804235.6750.129
Human front view
Model 136.84748133
Model 254.2217,38 (relative to Model 1)55413631940<0,0001
Model 353.5616,72 (relative to Model 1)58473631633<0,0001
Model 481.5627,35 (relative to Model 2)34203932120<0,0001
Model 581.35−0,22 (relative to Model 4)3309423112<0,0001
Model 681.38−0,18 (relative to Model 4)338942331.66<0,0001
Monkey 30-degree
Model 135.32691333
Model 257.4022,08 (relative to Model 1)43143632622<0,0001
Model 349.3614,04 (relative to Model 1)51793631757<0,0001
Model 484.0426,64 (relative to Model 2)23593931977<0,0001
Model 584.880,84 (relative to Model 4)233542348<0,0001
Model 684.080,04 (relative to Model 4)233142328<0,0001
Human 30-degree
Model 137.40681933
Model 255.7218,32 (relative to Model 1)48433631975<0,0001
Model 354.3616,96 (relative to Model 1)52173631602<0,0001
Model 481.3225,6 (relative to Model 2)29103931956<0,0001
Model 582.881,56 (relative to Model 4)2809423101<0,0001
Model 681.920,6 (relative to Model 4)2890423190.0002
Appendix 1—table 2
Parameters of the Bayesian motion morphing algorithm.

The observation matrix Y is formed by N samples of dimension D, where N results from S * E trails with T time steps. The dimensions M and Q of the latent variables were manually chosen. The integers …

Parameters of motion morphing algorithm
ParametersDescriptionValue
DData dimension208
MFirst layer dimension6
QSecond layer dimension2
TNumber of samples per trial150
SNumber of species2
ENumber of expressionstwo or 3
NNumber of all samplesT * S * E
Hyper parameters (learned)Size
β1Inverse width of kernel k11
β2Inverse width of kernel k21
β3Inverse width for non-linear part one of kernel k31
β4Inverse width for non-linear part two of kernel k31
γ1Precision absorbed from noise term εd1
γ2Variance for non-linear part of k11
γ3Variance for linear part of k11
γ4Variance for non-linear part of k21
γ5Variance for linear part of k21
γ6Variance for non-linear part of k31
γ7Variance for linear part one of k31
γ8Variance for linear part two of k31
VariablesSize
YDataN x D
HLatent variable of first layerN x M
XLatent variable of second layerN x Q
s^MStyle variable vector for monkey speciesS x 1
s^HStyle variable vector for human speciesS x 1
e^1Style variable vector for expression oneE x 1
e^2Style variable vector for expression twoE x 1
Appendix 1—table 3
Detailed results of the two-way ANOVAs.

ANOVA for the threshold: two-way mixed model with expression type as within-subject factor and the stimulus type as between-subject factor for both the monkey and the human avatar. Steepness: …

ANOVAs
ThresholdMonkey avatarSum of squaredfMean squareFp
Stimulus type0,0020,000,000999
Expression type1,2011,20188,830000
Stimulus * Expression0,0620,034,510015
Error0,42600,01
Total1,7265
Human avatar
Stimulus type0,0020,000,010993
Expression type0,4010,4046,370000
Stimulus * Expression0,0520,033,150049
Error0,57600,01
Total1,0265
SteepnessOriginal motion stimulus
Avatar type376,681376,686,30016
Expression type0,3610,360,010939
Avatar * Expression0,1610,1600959
Error2391,214059,78
Total2768,4143
Occluded motion stimulus
Avatar type286,171286,173,330076
Expression type0,0210,0200988
Avatar * Expression0,0010,0000995
Error3094,543685,96
Total3380,7339
Equilibrated motion stimulus
Avatar type1,5711,570,40533
Expression type0,2510,250,060803
Avatar * Expression0,0210,0200945
Error174,76443,97
Total176,6047

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