Deceptive Speech Frank Enos April 25, 2005. Defining Deception Deliberate choice to mislead a target without notification (Ekman‘’01) Often to gain some

Deceptive Speech

Frank Enos • April 25, 2005

Defining Deception

Deliberate choice to mislead a target without

notification (Ekman‘’01)

Often to gain some advantage

Excludes: Self-deception Theater, etc. Falsehoods due to ignorance/error Pathological behaviors

Why study deception?

Law enforcement / Jurisprudence

Intelligence / Military / Security

Business

Politics

Mental health practitioners

Social situations Is it ever good to lie?

Why study deception?

What makes speech “believable”?

Recognizing deception means recognizing

intention.

How do people spot a liar?

How does this relate to other subjective

phenomena in speech? E.g. emotion,

charisma

Problems in studying deception?

Most people are terrible at detecting

deception — ~50% accuracy

(Ekman & O’sullivan 1991, etc.)

People use subjective judgments —

emotion, etc.

Recognizing emotion is hard

Problems in studying deception?

Hard to get good data Real world Laboratory

Ethical issues Privacy Subject rights Claims of success

But also ethical imperatives: Need for reliable methods Debunking faulty methods False confessions

Frank Tells Some Lies

Maria: I’m buying tickets to Handel’s Messiah for me

and my friends — would you like to join us?

Frank: When is it?

Maria: December 19th.

Frank: Uh… the 19th…

Maria: My two friends from school are coming, and

Robin…

Frank: I’d love to!

How to Lie (Ekman‘’01)

Concealment

Falsification

Misdirecting

Telling the truth falsely

Half-concealment

Incorrect inference dodge.




Frank: When is it?



Maria: My two friends from school

are coming, and Robin…

Frank: I’d love to!

• Concealment

• Falsification

• Misdirecting

• Telling the truth falsely

• Half-concealment

• Incorrect inference dodge.




Frank: When is it?



Maria: My two friends from school

are coming.

• Concealment

• Falsification

• Misdirecting

• Telling the truth falsely

• Half-concealment

• Incorrect inference dodge.Frank: Oh gee, I’m having an appendectomy that night.

Reasons To Lie (Frank‘’92 )

Self-preservation

Self-presentation

*Gain

Altruistic (social) lies

How Not To Lie (Ekman‘’01)

Leakage Part of the truth comes out Liar shows inconsistent emotion Liar says something inconsistent with the lie

Deception clues Indications that the speaker is deceiving Again, can be emotion Inconsistent story


Bad lines Lying well is hard Fabrication means keeping story straight Concealment means remembering what is omitted All this creates cognitive load harder to hide emotion

Detection apprehension (fear) Target is hard to fool Target is suspicious Stakes are high Serious rewards and/or punishments are at stake Punishment for being caught is great


Deception guilt (vs. shame) Stakes for the target are high Deceit is unauthorized Liar is not practiced at lying Liar and target are acquainted Target can’t be faulted as mean or gullible Deception is unexpected by target

Duping delight Target poses particular challenge Lie is a particular challenge Others can appreciate liar’s performance

Features of Deception

Cognitive Coherence, fluency

Interpersonal Discourse features: DA, turn-taking, etc.

(Some addressed by Statement Analysis)

Emotion

Describing Emotion

Primary emotions Acceptance, anger, anticipation, disgust, joy,

fear, sadness, surprise

One approach:

continuous dim. model (Cowie/Lang)

Activation – evaluation space

Add control/agency

Primary E’s differ on at least 2 dimensions of this

scale (Pereira)

Problems With Emotion and Deception

Relevant emotions may not differ much on

these scales

Othello error People are afraid of the police People are angry when wrongly accused People think pizza is funny

Brokow hazard Failure to account for individual differences

20th Century Lie Detection

Polygraph http://antipolygraph.org

The Polygraph and Lie Detection (N.A.P. 2003)

Voice Stress Analysis Microtremors 8-12Hz Universal Lie response http://www.love-detector.com/ http://news-info.wustl.edu/news/page/normal/669.html

Reid Behavioral Analysis Interview Interrogation

Deception Experiments (Frank‘’92)Addresses lying as dependent variable.

Type and form of lie Concealment Falsification Misdirecting Telling the truth falsely Half-concealment Incorrect inference

dodge.

Motive for Lying Self-preservation Self-presentation Gain Altruistic (social) lies

Deception Experiments (Frank‘’92)Addresses lying as dependent variable.

Scenario *Topic of the lie: opinion; state; event. Stakes for lying / stakes for telling the truth. Interval between event and subject’s account.

Interpersonal structure Characteristics of the liar Characteristics of the target Presence or absence of a “coach” Presence or absence of others

The Good Old Days

Mehrabian 1971:

Nonverbal Betrayal of Feeling

Bulk of extant deception research…

Not focused on verifying 20th century

techniques

Done by psychologists

Considers primarily facial and physical cues

“Speech is hard”

Little focus on automatic detection of

deception

Modeling Deception in Speech

Lexical

Prosodic/Acoustic

Discourse

Deception in Speech (Depaulo ’03)

Positive Correlates Interrupted/repeated words References to “external” events Verbal/vocal uncertainty Vocal tension F0

Deception in Speech (Depaulo ’03)

Negative Correlates Subject stays on topic Admitted uncertainties Verbal/vocal immediacy Admitted lack of memory Spontaneous corrections

Problems, revisited

Differences due to: Gender Social Status Language Culture

Columbia/SRI/Colorado Corpus

With Julia Hirschberg, Stefan Benus, Sarah Friedman, Sarah Gilman, and colleagues from SRI/ICSI and U. C. Boulder

Goals Examine feasibility of automatic deception

detection using speech Discover or verify acoustic/prosodic, lexical,

and discourse correlates of deception Model a “non-guilt” scenario Create a “clean” corpus


Inflated-performance scenario

Motivation: financial gain

and self-presentation

32 Subjects: 16 women, 16 men

Native speakers of Standard American English

Subjects told study seeks to identify people who

match profile based on “25 Top Entrepreneurs”


Subjects take test in six categories: Interactive, music, survival, food,

NYC geography, civics

Questions manipulated 2 too high; 2 too low; 2 match

Subjects told study also seeks people who can convince interviewer they match profile Self-presentation + reward

Subjects undergo recorded interview in booth Indicate veracity of factual content of each utterance using

pedals

CSC Corpus: Data

15.2 hrs. of interviews; 7 hrs subject speech

Lexically transcribed & automatically aligned

lexical/discourse features

Lie conditions: Big Lie / Little Lie

Segmentations (LT/LL):

slash units (5709/3782), phrases

(11,612/7108), turns (2230/1573)

Acoustic features (± recognizer output)

CSC Corpus: Results

Classification (Ripper rule induction, randomized 5-fold cv) Slash Units / Little Lies — Baseline 39.8% err

Lexical & acoustic: 37.2 %; + subject dependent: 33.6% Phrases / Little Lies — Baseline 38.2% err

Lexical & acoustic 34.0%; + subject dependent: 27.9%

Other findings Positive emotion words deception (LIWC) Pleasantness deception (DAL) Filled pauses truth Some pitch correlation — varies with subject

Our Future Work

Individual differences Wizards of deception

Mark Frank Mock Theft Paradigm

New paradigm Shorter Addition of personality test Higher stakes?

Documents

Deceptive Speech Frank Enos April 25, 2005. Defining Deception Deliberate choice to mislead a target without notification (Ekman‘’01) Often to gain some