Within-trial repetitive transcranial magnetic stimulation (rtms) affects belief bias in conditional reasoning.

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1 Within-trial repetitive transcranial magnetic stimulation (rtms) affects belief bias in conditional reasoning. Matt Roser, Jonathan Evans, Lauren Carroll, Nick McNair, Giorgio Fuggetta, Anna Kharko RES

2 Jonathan Evans Nick McNair Giorgio Fuggetta Lauren Carroll Anna Kharko

3 Belief bias in conditional inference Many cognitive biases influence reasoning and decision making Performance on reasoning tasks often diverges from normative correctness but at least some people can reason analytically on these tasks We studied Belief Bias in conditional reasoning. This is manifest as a tendency to endorse more inferences derived from believable conditional statements, regardless of logical validity In the dual-process framework type 1(intuitive) processes cause the belief bias which may or may not be overridden by type 2(reflective) processes Individuals of higher cognitive ability (and WMC) are more likely to inhibit the effects of believability in conditional reasoning, under the right conditions

4 Questions - what neural systems are involved in conditional reasoning? - how is believability processed in the brain? - what distinguishes those more or less susceptible to belief bias in terms of neural activity? - in particular, do those showing less belief bias, show more evidence of inhibition and/or more evidence of engagement of analytic reasoning - By selectively impairing areas implicated in reasoning and belief can we modulate belief bias?

5 Our previous fmri study Three-term conditional statements comprised the Major Premise (MajP), Minor Premise (minp), and Conclusion (C) Conditionals described causal relationships about the world Half of the MajP statements were believable, half unbelievable BOLD modelled for major premise (P 1 ) and for entire argument (P ALL ) + Major Premise Major Premise Minor Premise Confidence + Conclusion 1 sec 4-6 sec Response Response 3-5 sec Split presentation allows separation of the sentence containing the belief content (the major premise) from the content that allows reasoning to begin (the minor premise and conclusion)

Our previous fmri study Reasoning Task > Control for

Contrasted Believable/Unbelievable for Major premise

extracted signal strength for each ROI P1 > Control

6 Our previous fmri study Reasoning Task > Control for Major premise (P1) and Entire Argument (PAll) Contrasted Believable/Unbelievable for Major premise and Entire Argument Correlated Belief-Bias index with extracted signal strength for each ROI P1 > Control Task PAll > Control Task P1: Unbelievable > Believable PAll: U>B

7 Within-trial rtms in Conditional Reasoning Tsuji et al. (2010) 10 minutes rtms right and left IFG RIFG enhanced BB, LIFG eliminated BB

8 Within-trial rtms in Conditional Reasoning Investigate stages of Major-Premise (MajP) processing (believability apparent) and Minor-Premise (minp) (Between subjects) Investigate functional regions such as DLPFC (working memory) and IFG (inhibition), informed by group fmri de-normalised to individual Cross these two factors in a 2x2 design: MajP IFG MajP DLPFC minp IFG minp DLPFC MajP - Decontextualisation of materials and the suppression of belief may occur following the MajP. minp - Effortful combination of premises and the derivation of a conclusion An effect of rtms over IFG for MajP, but not for minp, coupled with an effect of rtms over DLPFC for minp but not for MajP would doubly dissociate the MajP and minp stages and inform on processing in conditional reasoning

9 Design Separate stages (MajP and mp) between subjects Six sites of stimulation: - following fmri results Left DLPFC, Right DLPFC, Left IFG, Right IFG, Vertex stimulation, Vertex sham Six Blocks, one for each site, order randomised. Each block includes 24 trials (half un/believable) Each trial approx 7 seconds, with three seconds ITI. Block approx 5 minutes. 5 pulses per trial x 24 trials = 120 pulses per block at 10Hz, 80% of AMT 6 minute rest between blocks to avoid carryover. Total task = 1 hour rtms plus 30 mins Operation Span

10 Stimuli and Task 36 Statements rated for Believability (2) 18 believable, 18 unbelievable Forms (4) MP, MT, AC, DA, balanced across believability within each block 2x4x18 = 144 stimuli Instructed to decide whether the conclusion follows by logic. Told that half do.

11 Stimuli Pared-down statements Centrally presented word by word 500ms per word, 1 sec between premises 8 sec for response BREATHING DEAD THEN + IF

12 Within-trial rtms in Conditional Reasoning IF DEAD THEN BREATHING (1 sec) DEAD (Consequent) Major premise Minor premise (1 sec) BREATHING Conclusion

17 Results Raw data showed little belief bias and little evidence for experimental rtms effects Noise introduced by numerous departures from orthodox paradigm Pared-down (impoverished) statements Word-by-word presentation Chin rest and TMS distraction TMS power adjustment for comfort Large number of repeated trials We thus had behavioural (e.g. extreme endorsement rate/latency) and TMS (navigation, level) factors to consider in excluding data from analysis.

not get a reliable AMT removed Block/location data for participants that

18 Results Exclusions: Blocks 1-3 only Individual trials with RTs > 3SDs from participant's individual mean overall RT removed Participants for whom we did not get a reliable AMT removed Block/location data for participants that received TMS intensity level <40% power N = 25 for each Premise/Time Major Premise Minor Premise

19 Results Exclusions: Blocks 1-3 only Individual trials with RTs > 3SDs from participant's individual mean overall RT removed Participants for whom we did not get a reliable AMT removed Block/location data for participants that receiving TMS intensity level <40% power N = 25 for each Premise/Time

20 Results Results differed from predictions, particularly the lack of Right IFG and Left DLPFC rtms effect LIFG effect opposite to Tsuji (2010) and RIFG effect absent Note the temporal-specificity and task (conditional v syllogistic) differences Effect of Left IFG rtms consistent with the central role of this region in reasoning Major Premise Minor Premise

High endorsement of MP precludes belief bias Incorporate

21 Further? Major Premise Investigate effects within logical forms? Reverse inferences MT and AC? High endorsement of MP precludes belief bias Incorporate cognitive-ability (WM) data? No correlation of WM and BB, but effects may differ for high and low ability subjects Minor Premise

22 Inference follows Reinstate Draw No Yes Yes Withhold Believable? Check reasoning No Withhold Yes No Draw Withhold Reinstatement of inference in opposition to belief Greatest in high IQ, leading to less BB Low IQ experience relatively greater demand on WM resources when reasoning with unbelievable materials and are less able to reinstate the valid inference

Experimental Design I

Experimental Design I Topics What questions can we ask (intelligently) in fmri Basic assumptions in isolating cognitive processes and comparing conditions General design strategies A few really cool experiments