1. Reasoning distinctions: Induction vs. Deduction or System 1 vs. System 2? Aidan Feeney, Darren Dunning & David Over Durham University

2. Rosemary Stevenson

5. What if we assume that p and q are rare?

6. Talk Overview Reasoning distinctions –Dual processes –A problem-based dissociation: Induction vs. deduction Induction and deduction –To what extent are they dissociable (see Rips, 2001)? –What is the relationship between the problem-based dissociation and the dual process idea? –Two individual differences studies Conclusions

7. Dual Process Theories (Evans & Over, 1996; Stanovich, 1999; Sloman, 1996) Suggest that there are two types of thinking Type 1 Evolutionarily older Fast Massively parallel Implicit Associative Unrelated to general cognitive ability Type 2 More recent Slow Sequential Explicit Symbol manipulating Related to general cognitive ability

8. Dissociating Types of Thinking Belief bias effect (Evans, Barston & Pollard, 1983) VALID BELIEVABLE No police dogs are vicious Some highly trained dogs are vicious Therefore, some highly trained dogs are not police dogs INVALID BELIEVABLE No addictive things are inexpensive Some cigarettes are inexpensive Therefore, some addictive things are not cigarettes VALID UNBELIEVABLE No nutritional things are inexpensive Some vitamin tablets are inexpensive Therefore, some vitamin tablets are not nutritional INVALID UNBELIEVABLE No millionaires are hard workers Some rich people are hard workers Therefore some millionaires are not rich people

9. Findings Effects of validity and beliefs (Evans et al 1983) Belief-based and logical responding are neuropsychologically dissociated (Goel et al., 2003) Effects of beliefs –Greater with age (Gilinsky & Judd, 1994) –Greater under speeded conditions (Evans & Curtis-Holmes, 1995) –Decreased by strong emphasis on logical necessity Tendency to resist effects of belief associated with cognitive ability (Stanovich, 1999)

10. An alternative dissociation - Induction vs. Deduction Rips (2001) – Are inductive and deductive arguments evaluated in the same way? Sought to counter ‘reasoning imperialism’ of mental models and probabilistic approaches Single continuum view

11. Evidence for a dissociation Rips (2001) - Ran a belief bias experiment with inductive and deductive instructions Valid Consistent If car X10 runs into a brick wall, it will stop Car X10 runs into a brick wall Car X10 will stop Invalid Consistent Car X10 runs into a brick wall Car X10 will stop Valid inconsistent If car X10 runs into a brick wall, it will speed up Car X10 runs into a brick wall Car X10 will speed up Invalid Inconsistent Car X10 runs into a brick wall Car X10 will speed up

12. Dissociation between Induction and Deduction

13. Relationships between the dissociations 1.Some form of equivalence Induction involves inference about what is plausible – based on all relevant belief –Might involve Type 1 processes Deduction involves inference about what is necessary – requires decontextualisation or inhibition of belief –Involves Type 2 processes

14. Evidence Feature-Based Model (Sloman, 1993) –Associationist account in which argument strength is related to the amount of featural overlap between the categories in the premises and conclusion Feeney (in submission) –Sensitivity to some of the key phenomena in category-based induction associated with cognitive ability

15. 2. They are orthogonal to each other There are two types of thinking but these do not correspond to deduction and induction –One type is sensitive to abstract structure and the other to pragmatic/belief-based influences –One type is constrained, the other is not Predictions –Might expect logical structure to affect reasoning even under inductive instructions – but only for the highest ability participants –Beliefs should also affect reasoning - open question as to whether it will interact with ability Relationships between the dissociations

16. 3. The problem-based dissociation is the product of Type 2 processes Rips’ dissociation is just another effect of instructions – mediated by Type 2 processes Would expect to find more evidence of a dissociation amongst participants high in ability

17. Two Studies Study 1: Individual differences in reasoning under inductive instructions Contrasts possibilities 1 and 2 Study 2 Individual differences method combined with inductive and deductive instructions Contrasts possibilities 2 and 3

18. Study 1 81 participants All given induction instructions – how plausible do the premises make the conclusion? Attempted 16 problems each –valid consistent –valid inconsistent –invalid consistent –invalid inconsistent All Ps attempted AH4 Overall mean 94.4 Two groups –Low ability Mean = 84.2, N = 41 –High ability Mean = 104.8, N = 40

19. Figure 1: Ability X Validity and Ability X Consistency interactions.

20. Figure 2: Interaction between Ability, Validity and Consistency. * * *

21. Discussion Even under inductive instructions some people are more sensitive to logical structure than others These people tend to be highest in cognitive ability The dissociations are not equivalent – induction is not achieved solely by Type 1 processes

22. Study 2 151 participants Given deduction or induction instructions –Necessity vs. plausibility Valid vs. invalid Strong vs. Not Strong Attempted 16 problems each –valid consistent –valid inconsistent –invalid consistent –invalid inconsistent All Ps attempted AH4 Overall mean 98.0 Two groups –Low ability Mean = 85.6, N = 74 –High ability Mean = 109.9, N = 77

23. Figure 3: Ability X Validity and Ability X Consistency interactions.

24. Figure: 4: Interaction between Validity, Consistency and Instructions

25. Figure 5: Interaction between Ability and Condition

26. Discussion Under inductive and deductive instructions some people are more sensitive to logical structure than others These people tend to be highest in cognitive ability Weaker indication of a dissociation between induction and deduction Problem-based dissociation does not appear to be due to System 2 processes

27. Outstanding Issues Where does the deduction/induction dissociation come from? From a dual process perspective it should be mediated by System 2 processes. Type 1 induction Type 2 induction Type 1 deduction Type 2 deduction