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Commonsense reasoning

Commonsense reasoning. Cognitive Science Week 10. Which information is relevant to drawing a conclusion? Which facts are affected by an event? • Yale shooting problem • Property inheritance Tweety is a bird. So Tweety can fly?. Frame problem Draw finger over a wall. What changes?

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Commonsense reasoning

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  1. Commonsense reasoning Cognitive Science Week 10

  2. Which information is relevant to drawing a conclusion? • Which facts are affected by an event? • • Yale shooting problem • • Property inheritance • Tweety is a bird. So Tweety can fly?

  3. Frame problem • Draw finger over a wall. What changes? • Wet paint? • Pour juice from one beaker to another. • - What changes? What remains the same? • • Qualification problem - boats, cars & chickens

  4. Monotonic v. non-monotonic inference • monotonic inference • holds even if new information is added • non-monotonic inference • new information can invalidate

  5. Ways to formalise non-monotonic inference • Frame axiom • painting one object (2) doesn't affect the location of another object (1) • Location [obj-1, loc-x, sit-a]  • Location [obj-1, loc-x, paint (obj-2, colour, sit-a)] • obj-1 stays in loc-x

  6. Closed World Assumption • If it isn't in the database, it isn't - all relevant information is to hand. • Cov Euston • 0805 0915 • 0835 0950 • 0845 1000 • 0910 1030 • Is there a train at 9am?

  7. Possible Worlds • Take three propositions, P, Q & R • There are several possible interpretations, or models: • P Dad is gardening; Q mum is reading; R wee Johnny is playing • P Q R • T T T • T F T • T T F • F T T • etc.

  8. Possible: there's at least one possible world in which the proposition is satisfied • P R "possibly Johnny is playing" • N P "necessarily Dad is gardening“ • P Q not N not Q

  9. Modal operators • McDermott & Doyle (1980); Moore (1985) • Operator M - 'maybe‘; if consistent with all else known • Bird (x) & M Fly (x)  Fly (x) • Formalise M in terms of modal operators • Bird (x) & not N not Fly (x)  Fly (x) • If x is a bird and it is consistent that it can fly, then it can fly. Or 'typically birds can fly'. • Exceptions indicated by sentences: • Penguin (x)  not Fly (x)

  10. Car(x) & M Got_petrol(x)  Got_petrol(x) • This is a default rule • … believe that cars have petrol unless you have a reason to doubt it • Siphoned(x)  not Got_petrol(x)

  11. Extensions of the database • When checking whether something is consistent, you extend the database of facts: • all facts already known • + all facts you can deduce from regular inference rules • + anything you can deduce using default rules

  12. Multiple extensions problem • Quaker(x) & M Pacifist(x) •  Pacifist (x) • Republican(x) & M not-Pacifist(x) •  not-Pacifist(x) • Quaker (Nixon), Republican (Nixon) •  Pacifist (Nixon) & not Pacifist (Nixon)

  13. How choose? • 1. prioritise rules • a ‘fix’ • 2. world knowledge

  14. Natural reasoning • Non-monotonic reasoning in the lab (Byrne, 1989) • Inference "suppressed" by adding information • If John hasn't finished his essay, then he will go to the library tonight. • John hasn't finished his essay. • + If the library is open, John will go to the • library tonight.

  15. Stevenson & Over (1995) • Can vary this effect by qualifying certainty • If John goes fishing, he will have fish for tea. • John goes fishing. • If John goes fishing, and if he catches a fish, he will have fish for tea. • John goes fishing. • If John goes fishing, he will have fish for tea. John is always / usually / never lucky as a fisherman. • John goes fishing.

  16. Beliefs (world knowledge) affect reasoning • Oakhill, Johnson-Laird, & Garnham (1989) • All the Frenchmen are gourmets. • Some of the gourmets are wine drinkers. Some of the Frenchmen are wine drinkers 72 % All the Frenchmen are gourmets. Some of the gourmets are Italians. Some of the Frenchmen are Italians. 8 %

  17. Belief bias • Evans, Barston & Pollard (1983) • No nutritional things are cheap • Some vitamin tablets are cheap Some vitamin tablets not nutritional

  18. Illusion of explanatory depth • Rozenblit & Keil (2002) • students rate how well they understand (48) devices and phenomena • How a snare catches small animals • How a computer mouse controls the cursor • … then write detailed explanations for 4 • Re-rate self-understanding (ratings drop) • Rate explanations independently (closer to the re-rating)

  19. Core reading: • Eysenck & Keane (2000). Cognitive psychology: A student handbook, 4th Edition. Chapters 16 (up to page 460) and 17. • Rozenblit & Keil (2002). The misunderstood limits of folk science: an illusion of explanatory depth. Cognitive Science, 92, 1-42. • Wilson & Keil (Eds.) (1999). The MIT Encyclopedia of Cognitive Science. (On the Science reference shelves in the Library.) Entries and essays on: BOUNDED RATIONALITY; FRAME PROBLEM; NONMONOTONIC REASONING. • And see other links on the module web page. • The Enclyclopedia is available from the Library as an electronic book

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