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Stimulation Affects Belief Bias in ReasoningStimulation Affects Belief Bias in ReasoningStimulation Affects Belief Bias in Reasoning M. E. RoserM. E. RoserM. E. Roser111., J. S. T. Evans., J. S. T. Evans., J. S. T. Evans111., L. S. Carroll., L. S. Carroll., L. S. Carroll111., N. A. McNair., N. A. McNair., N. A. McNair222., G. Fuggetta., G. Fuggetta., G. Fuggetta333., and A. Y. Kharko., and A. Y. Kharko., and A. Y. Kharko111

111School of Psychology, Plymouth University, UK. School of Psychology, Plymouth University, UK. School of Psychology, Plymouth University, UK. 222University of Sydney, AUS University of Sydney, AUS University of Sydney, AUS 333University of Leicester, UK.University of Leicester, UK.University of Leicester, UK.

[1] OVERVIEW

Aim: To investigate the effect of rTMS on belief bias in conditional reasoning. Specifically, whether selectively impairing brain regions implicated in reasoning and belief may mod-ulate belief bias.

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[5] PROCEDURE:

Three-term conditional statements. Participants were instructed to assume all infor-mation in the premises was true and to determine whether the conclusion followed ac-cording to logic. Pared-down statements and word-by-word presentation was used to force reading speed and provide the temporal specificity needed for time locking rTMS stimulation to immediately after the premises. Six blocks of 24 trials each (half un/believable). Logical forms (4) MP, MT, AC, DA, bal-anced across believability within each block. One TMS location per block (order random-ised). TMS 10Hz for 500ms at 80% of Active Motor Threshold (AMT) on each trial immediately

after the presentation of the major OR minor premise.

[3] OUR PREVIOUS fMRI CONDITIONAL REASONING STUDY:

We investigated the brain areas involved in conditional reasoning and belief bias. Our

previous fMRI study found activation in the right inferior frontal cortex (IFG; implicated in

inhibitory processing) at the major premise stage and the addition of activation in the left

dorsolateral prefrontal cortex (DLPFC; involved in working memory) when the whole ar-

gument was presented (minor premise) which correlated with degree of belief bias.

[2] BACKGROUND:

Decision making is influenced by cognitive biases which may impair reasoning ability. We studied Belief Bias in conditional reasoning. Belief bias is the tendency to endorse more inferences derived from conditional statements if they are believable, regardless of logi-cal validity. Dual process theories posit two distinct cognitive systems: Type 1 processes occur quickly and are automatic, whereas Type 2 processes are slower and require effort [1]. Default interventionist theories state that in order to perform well in a reasoning task in which there is conflict between logic and belief, responders must inhibit and overcome initial in-tuitive belief-based judgements (type 1) in favour of more systematic logical processing (type 2). This is effortful and requires cognitive resources and working memory (WM) [2]. Individuals with high IQ and WMC typically perform better at these tasks. The roles of in-hibitory and WM processes in determining individual differences remain unresolved.

[4] CURRENT rTMS STUDY:

Based on our fMRI results, we targeted 6 locations for rTMS: Left IFG, Left MFG, Right IFG, Right MFG, Vertex stimulation (Cz), Vertex sham (Cz*; note: these included lateral homo-logues of fMRI findings and two control locations). We applied within-trial rTMS to these areas, manipulating the stage of processing targeted between subjects. Functionally ac-tive regions from our fMRI were de-normalised into each individual’s brain space as TMS target locations.

[6] THE TASK: (Unbelievable modus ponens example)

IF DEAD THEN BREATHING [Major premise]

DEAD [Minor premise]

BREATHING [Conclusion]

Does the conclusion logically follow?

[10] REFERENCES:

[1] Evans, J. S. B. (2008). Dual-Processing accounts of Reasoning, Judgement, and Social Cognition. Annu. Rev. Psychol., 59, 255-278

[2] Handley, S., Capon, A., Beveridge, M., Dennis, I., & Evans, J. S. B. (2004). Working Memory, Inhibitory Control and the Development of Children’s Reasoning. Thinking and

Reasoning, 10, 175-195

[9] CONCLUSION:

Results differed from predictions, particularly the lack of Right IFG and Left DLPFC rTMS effect.

rTMS to the left IFG increased susceptibility to belief bias, suggesting that the left IFG in particular is involved in the moderation of belief bias and plays a central part in reason-ing. rTMS to the left IFG may have disrupted the analytical (type 2) processing of condi-tionals at the major and minor premise stage of the task thus increasing the likelihood of participants reverting to automatic (type 1) processes and giving a default heuristic re-sponse which may have been biased by the believability of the statements.

These results are consistent with a model of concurrent processes of inhibition and inte-gration rather than discreet stages.

[7] RESULTS

Overall results showed little belief bias or evidence for experimental rTMS effects. How-ever, this may be as our study differed from orthodox reasoning paradigms due to meth-odological changes necessitated to run the study with TMS (e.g., pared-down structure, TMS distraction, much greater number of trials).

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Block 1 Block 2 Block 3 Block 4 Block 5 Block 6Be

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Block order

Belief bias by blockThe extensive number of trials and practise effects resulted in little or no belief bias past block 4. Therefore, we focused on data from the first 3 blocks only as this more closely repli-cated traditional reasoning studies.

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Left IFG Left MFG Right IFG Right MFG Mean Sham

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TMS Location

Belief bias by TMS location

Major Premise (T1)

Minor Premise (T2)

[8] DATA FROM BLOCKS 1-3: Exclusions: Blocks 1-3 only Individual trials with

RTs>3SDs from each participant’s individu-al overall RT removed

Data for participants for whom we did not get a reliable AMT

Block/location data if TMS intensity was dropped below 40% P1 > Control task PAll > Control

WEBSITE/MORE INFO:

www.psy.plymouth.ac.uk/research/mattroser

Left: Individual extracted brain image with TMS target locations mapped

Middle: Brainvoyager TMS real-time neuronavigation guide

Right: The experimental set-up

This work was supported by the Economic and Social Research Council Grant: RES- 062-23-3285