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. CovEuston 08050915 08350950 08451000 09101030 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 PQR TTT TFT TTF FTT 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 QnotN 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 drinkers72 % 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 BelievableUnbelievable Valid89%56% Not Valid 71%10%

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