“What if” and “If only” thoughts about imagined alternatives to Co Cons nstraints on n reality Co Coun unterfactua uals Counterfactuals How a decision in the past could Ruth M.J. Byrne Ru have been different, or how one in Tr Trinity College Dublin the future could be different University of Dublin, Ireland Un XAI workshop keynote IJCAI19 Macao, China Many uses of counterfactuals in AI eXplainable AI (XAI) Decisions of complex AI Artificial neural AI systems to explain systems networks (ANNs) decisions to humans e.g., criminal sentencing, trained on vast amounts to increase trust by Sub-goals; planning Counterfactual Generative adversarial creditworthiness, of data; can produce users, accuracy in failures; fault diagnosis risk/regret minimization networks (GANS) automated vehicles unintelligible decisions training by developers Ginsberg, 1986; Halpern & S waminathan & Joachims, Pearl, 2005 2015 ; Moravčík et al., 2017 Neal et al., 2018 Biran & Cotton, 2017; Weld & Bansal, 2018 Examples Contrastive explanations; why one decision was Counterfactuals made instead of another in XAI Categorisation Creditworthiness Autonomous vehicles Hoffman et al., 2018; McGrath et al., 2018; What if feature A had If the applicant’s income If only the car had Miller, 2019; Wachter et al., 2018 had a higher weighting, were $10,000 higher, braked instead of would the selected their loan application swerving, the crash category have been would be approved. would have been different? avoided. 1
Number is potentially limitless 1. 1. Human counter erfactual thought What to change? Not all are equally helpful for Which Wh humans 2. 2. Men ental model els of counter erfactuals ‘Minimal’ change is slippery counterfactuals? co concept 3. How peo 3. eople e crea eate e counter erfactuals Evidence from human reasoners Which counterfactuals do people create, how do people reason about counterfactuals? Human Two enduring questions in cognitive counterfactual science Are people rational? thought Does the mind have the How Are People Creative? competence to make inferences, constrained by performance? 2
How does the human mind make discoveries, create new ideas, engage in literature and art? Reason and Creativity Counterfactuals bridge reasoning and creativity Pe People can create rich alternatives to reality We often imagine We how thi ho hing ngs coul uld d ha have tur urne ned ou out differ eren ently y ‘if on only… y…’ Al Alternatives to reality entertain us – us usua ually after ba bad d out utcomes but but the hey al also pl play ay a a more serious us role. By Byrn rne 2016 Annual Review of Psychology Kahneman & Tversky 1982 3
The They he help p us us to expl plain n the he pa past The They he help p us us to pr prepa pare for the he fut utur ure We can use them to work out causes We can learn from mistakes, form intentions, make decisions McCrae 2008; Spellman & Mandel 1999; Roese & Epstude, 2017; Ferrante et al., 2013; Dixon & Byrne 2011 Memory & Cognition McEleney & Byrne, 2006; Walsh & Byrne, 2007 Thinking & Reasoning Mo Moral judgments Emotions Em Blame, fault, responsibility Regret, guilt, relief, hope Malle et al., 2014; Alicke et al., 2008; Roese & Epstude 2017; Sweney & Vohs 2012; Parkinson & Byrne, 2017 Judgment & Decision Makin g Byrne & McEleney, 2000 JEP: Learning, Memory & Cognition Byrne & Timmons, 2018 Cognition Lo Loss of imagination Cou Counter erfactual thou oughts em emer erge e ea early Injuries to the prefrontal cortex; an and develop through middle childhood Parkinson’s; Schizophrenia; Autism Harris, 2000; Beck et al., 2006; Gomez-Beldarrain et al., 2005 ; McNamara et al., 2003 Rasga, Quelhas & Byrne, 2016 Cognitive Development Rasga, Quelhas & Byrne, 2017 Journal of Autism and Developmental Disorders 4
Experimental evidence Methods Measures Remember episodes from own life Types of counterfactuals people create Read stories about hypothetical events Inferences from counterfactuals with fictional protagonists about How quickly people read counterfactuals accidents, illnesses, goal failures What is looked at for a counterfactual Engage in a task, e.g., solving a puzzle From Van Hoeck, Watson, & Barbey, 2015; Brain imaging of activated areas see also De Brigard, Addis, Ford, Schacter, & Giovanello, 2013 David Hume Illustration: Counterfactuals and Evidence from human Causes reasoners can maximize Ar Artificial effectiveness of XAI Imaginative Im Two sides of one coin? In Intelligence AI systems that A caused B (A (AII) construct same counterfactuals humans If A hadn’t happened, B naturally create wouldn’t have happened John Stuart Mill Hume, 1739/1978; Mill, 1843/1967; Lewis, 1973 Counterfactuals amplify causal judgments Example Counterfactual If the car had braked instead of swerving, different action - the passenger wouldn’t have been injured Decision to swerve to avoid hitting cyclist Autonomous different outcome Amplifies judgments of causal relation vehicle Outcome: hit wall, passenger minor injuries Even if the car had braked instead of Semi-factual swerving, the passenger would still have different action - been injured same outcome Reduces judgments of causal relation McCloy & Byrne, 2002 5
(1) But they focus on different sorts of causes (1) But they focus on different sorts of causes How could things have How could things have Story about car accident What was the cause of Story about car accident What was the cause of the accident? turned out differently? the accident? turned out differently? The drunk driver If the protagonist had driven The drunk driver If the protagonist had driven A drunk driver swerved into a A drunk driver swerved into a home by his usual route home by his usual route protagonist driving home on protagonist driving home on an unusual route an unusual route Strong causes that co-vary Background enabling with outcome; necessary conditions that could prevent and sufficient outcome; necessary and not sufficient Mandel & Lehman, 1996 Example (2) People spontaneously create twice as many causal thoughts as Diary entry Causal Counterfactual explanations thoughts about Spontaneous counterfactual thoughts about the facts imagined undirected as they alternatives thoughts happened If I had gone to Created twice as I didn’t make the party I many causal friends because I would have thoughts as didn’t go to the made friends counterfactuals party Alice McEleney McEleney & Byrne, 2006 Thinking & Reasoning McEleney & Byrne, 2006 Thinking & Reasoning (3) Cause-effect sequences (3) Cause-effect sequences CAUSE -Effect CAUSE -Effect Bad weather conditions caused the car Bad weather conditions caused the car accident accident If only the weather hadn’t been bad … If only the weather hadn’t been bad … Focus on cause Focus on cause Reason- ACTION Wanting to get milk was the reason the person drove to the shop If only he hadn’t driven to the shop… Clare Walsh Clare Walsh Focus on action Wells et al., 1989 Plymouth University Plymouth University 6
If AI agent provides counterfactual, human will readily infer a causal 1. 1. Human counter erfactual thought Implications relation 2. Men 2. ental model els of counter erfactuals for XAI But given the differences between causal and counterfactual thoughts, 3. 3. How peo eople e crea eate e counter erfactuals explicit causal explanations as well as counterfactual alternatives may be needed Truth functional semantics Unable to account for meaning of counterfactuals People construct a mental model Adams, 1975 Represent aspects of a situation Counterfactuals Counterfactuals in Cognitive and Mental Possible worlds semantics Create counterfactual Truth in the closest possible world Select aspect represented in model Science Models Lewis, 1973; Stalnaker, 1968 Modify to create an alternative model Closest possible world is ill-defined concept Byrne, 2002 Trends in Cognitive Sciences Kratzer, 2012; Williamson, 2007 If If the car turned, it hit the hi he cyclist People construct mental models turned hit to simulate possibilities not-turned not-hit not-turned hit Possibilities Johnson-Laird, 1983; 2006; Phil Johnson-Laird Byrne & Johnson-Laird, 2009 Trends in Cognitive Sciences Princeton University 7
If If the car turned, it If If the car turned, it hi hit the he cyclist hi hit the he cyclist turned hit turned hit not-turned not-hit … not-turned hit turned not-hit Principle of truth Principle of parsimony If the car turned, it If If the car had If had tu turned, it t hi hit the he cyclist would have hi wo hit the he cyclist Counterfactual turned hit turned hit … not-turned not-hit Fact … Working memory constraints Dual possibilities for counterfactuals 1. What do counterfactuals 1. imply im ly? Counterfactual Factual If the car had turned, it would have If the car had turned, it would have If the car turned, it hit the cyclist hit the cyclist hit the cyclist What does someone uttering the turned hit C’Fact turned hit assertion mean to imply? not-turned not-hit Fact … The car did not turn. … It did not hit the cyclist. Valerie Thompson Sasatchwan University Thompson & Byrne, 2002 Journal of Experimental Psychology: Learning Memory & Cognition 8
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