Free Will and the Brain Disease Model of Addiction: The Not So Seductive Allure of Neuroscience

17 Pages·2017·1.14 MB·English

by  Eric Racine

ORIGINALRESEARCH
published:01November2017
doi:10.3389/fpsyg.2017.01850
Free Will and the Brain Disease
Model of Addiction: The Not So
Seductive Allure of Neuroscience and
Its Modest Impact on the Attribution
of Free Will to People with an
Addiction
EricRacine1,2,3*,SebastianSattler1,4andAliceEscande1,5
1NeuroethicsResearchUnit,InstitutderecherchescliniquesdeMontréal,Montréal,QC,Canada,2BiomedicalEthicsUnit,
DivisionofExperimentalMedicine,DepartmentofNeurologyandNeurosurgery,McGillUniversity,Montréal,QC,Canada,
3DepartmentofMedicineandDepartmentofSocialandPreventiveMedicine,UniversitédeMontréal,Montréal,QC,Canada,
4InstituteforSociologyandSocialPsychology,UniversityofCologne,Cologne,Germany,5CognitiveScienceProgram,
McGillUniversity,Montréal,QC,Canada
Free will has been the object of debate in the context of addiction given that addiction
could compromise an individual’s ability to choose freely between alternative courses
Editedby: of action. Proponents of the brain-disease model of addiction have argued that a
ZoltanDienes, neuroscience perspective on addiction reduces the attribution of free will because it
UniversityofSussex,UnitedKingdom
relocates the cause of the disorder to the brain rather than to the person, thereby
Reviewedby:
diminishingtheblameattributedtothepersonwithanaddiction.Othershaveworriedthat
AndrewMonroe,
AppalachianStateUniversity, such displacement of free will attribution would make the person with a drug addiction
UnitedStates
lessresponsible.Usingtheparadigmaticliteratureontheseductiveallureofneuroscience
EmilieCaspar,
FreeUniversityofBrussels,Belgium explanations,wetestedwhetherneuroscienceinformationdiminishesattributionsoffree
*Correspondence: will in the context of addiction and whether respondent characteristics influence these
EricRacine attributionsandmodulatetheeffectofneuroscienceinformation.Weperformedalarge-
[e-mail]
scale,web-basedexperimentwith2,378Germanparticipantstoexplorehowattributions
Specialtysection: of free will in the context of addiction to either alcohol or cocaine are affected by: (1) a
Thisarticlewassubmittedto textwithaneurobiologicalexplanationofaddiction,(2)aneuroimageshowingeffectsof
ConsciousnessResearch,
addictiononthebrain,and(3)acombinationofatextandaneuroimage,incomparison
asectionofthejournal
FrontiersinPsychology to a control group that received no information. Belief in free will was measured using
Received:02December2016 theFAD-Plusscaleandwas,subsequenttofactoranalysis,separatedintotwofactors:
Accepted:04October2017
responsibilityandvolition.Theinvestigatedrespondentcharacteristicsincludedgender,
Published:01November2017
age, education, self-reported knowledge of neuroscience, substance-use disorder
Citation:
RacineE,SattlerSandEscandeA (SUD), and having a friend with SUD. We found that attributions of volition (in the
(2017)FreeWillandtheBrainDisease cocaine-subsample) were reduced in the text and neuroimage-treatment compared
ModelofAddiction:TheNotSo
to the control group. However, respondent characteristics such as education and
SeductiveAllureofNeuroscienceand
ItsModestImpactontheAttributionof self-reported knowledge of neuroscience were associated with lower attributions of
FreeWilltoPeoplewithanAddiction.
responsibilityforbothsubstances,andeducationwasassociatedwithlowerattribution
Front.Psychol.8:1850.
doi:10.3389/fpsyg.2017.01850 of volition for the alcohol sub-sample. Interaction analyses showed that knowledge
FrontiersinPsychology|www.frontiersin.org 1 November2017|Volume8|Article1850
Racineetal. FreeWillandAddiction
of neuroscience was found to generally decrease attribution of responsibility. Further
researchonattributionoffreewillshouldconsidertheeffectsofcontextandrespondent
characteristics, which appeared surprisingly larger than those induced by experimental
treatments.
Keywords:freewill,neuroimaging,addiction,responsibility,stigma,neuroscience,ethics
INTRODUCTION Nahmiasetal.,2014;Shariffetal.,2014).Indiscussionsaboutthe
braindiseasemodelofaddiction(seeexplanationbelow)andits
Free will is a commonly referenced but nevertheless complex implicationsfortreatmentandpolicies,theeffectofneuroscience
concept. It is used both in academic and public discourse to information on belief in free will could matter significantly.
describe an ability to choose between alternative courses of Neuroscienceinformationhasbeenclaimedtoreducethestigma
action (Stillman et al., 2011; Baumeister and Monroe, 2014; associated with addiction (Dackis and O’Brien, 2005) because
Monroe et al., 2014; Racine et al., 2017). In the context of beliefs about the free will of people, as well as the associated
addiction, free will has been an object of debate and scrutiny, attributions of blame and personal responsibility, are lessened
since addiction could compromise an individual’s ability to (Racineetal.,2015).Alternatively,neuroscienceinformationhas
choose freely (Levy, 2013). In the philosophical literature, free been claimed to increase stigma because decreased attributions
will is often considered an all-or-nothing property, and it has offreewillinfantilizeindividualswithanaddictionandportrays
been criticized for not capturing a positive ability of the agent themasdangerousbecausetheyareperceivedtolacksomebasic
per se, since it is often defined as the opposite of determinism requirement for decision-making and self-control (Hammer
(GertandDuggan,1979).Researchonbeliefinfreewill,which et al., 2013; Racine et al., 2015). Interestingly, other literature
includes a body of literature distinct from the long tradition on the seductive allure of textual neuroscience explanations
of philosophical scholarship on the topic, has brought more (Weisberg et al., 2008) or neuroimaging evidence (McCabe
attentiontofreewillasapsychologicalphenomenon,i.e.,abelief and Castel, 2008) has investigated whether specific forms of
or disposition that has behavioral and motivational effects and neuroscience information could sway beliefs about a host of
is thus amenable to psychological inquiry (Baumeister, 2008; phenomena (e.g., ratings of the value of scientific reasoning;
Baumeister and Monroe, 2014). This research has now shown explanations of psychological phenomena). In the following
thatbeliefinfreewillcanfluctuateandthatsuchfluctuationshave section, we further describe how the literature on the brain
implications. For example, belief in free will can be modulated disease model of addiction sets the stage for the importance of
by both personal characteristics (e.g., physiological desires, belief in free will on different aspects of addiction, while the
religious beliefs, political orientations, self-esteem) (Laurene literature on the seductive allure of neuroscience explanations
et al., 2011; Carey and Paulhus, 2013; Ent and Baumeister, proposesspecificapproachesthroughwhichthiseffectcouldbe
2014)aswellascontextualorinterpersonalcharacteristics(e.g., investigated.
promptsaboutcausaldeterminismdiminishingbeliefinfreewill,
differencesbetweenbeliefsaboutone’sfreewillvs.attributionto
Belief in Free Will and the Brain Disease
others) (Stroessner and Green, 1990; Vohs and Schooler, 2008;
Baumeister et al., 2009; Pronin and Kugler, 2010; Lynn et al., Model of Addiction
2014; MacKenzie et al., 2014; Nahmias et al., 2014). Moreover, There have been debates about the impact of a brain disease
changesinbeliefinfreewillhavebeenassociatedwithanumber modelofaddictiononanumberofinterwovenissuessuchasfree
of consequential implications on attitudes and behaviors. For will, responsibility, and stigma (notably blaming) (Levy, 2013;
example, reduced belief in free will has been associated with Hall et al., 2015; Racine et al., 2015). The core of the brain
diminishedself-control(Rigonietal.,2012)andhelpingbehavior diseasemodelofaddictionisthe“brain-hijacktheory”(Leshner,
(Krueger et al., 2014), as well as increased cheating (Vohs 1997; Volkow and Li, 2005). It posits that addiction is a brain
and Schooler, 2008), increased punishment responses (Krueger disease caused by a dysfunction of brain systems involved in
et al., 2014) and increased aggressive behavior (Krueger et al., reward and pleasure seeking. According to this view, a greater
2014). Higher belief in free will has been associated with more emphasis on the biological aspects of addiction is a gateway to
positive attitudes and behaviors, including ethically or socially greatersocialacceptanceofpeoplewithanaddiction(Dackisand
desirable behavior (e.g., higher belief in free will predicted O’Brien,2005;Hyman,2007).Indeed,thisinterestintheimpact
better job performance, Stillman et al., 2010; MacKenzie et al., ofneurosciencediscourseonbeliefinfreewillcanbeunderstood
2014). Obviously, these findings like others in psychology and notonlybecauseofitsphilosophicaldimensionsbutalsobecause
cognitivesciencecouldbeaffectedbyfailurestoreplicatefindings ofitspracticalrelevanceforanumberofissues(seeFigure1).
(OpenScienceCollaboration,2015;Ewusi-BoisvertandRacine, However,thebenefitsofthebraindiseasemodelofaddiction
inpress). onrelevantissuessuchasreductionofstigmaandresponsibility
Exposuretovisualandtextualneuroscienceexplanationsfor are disputed (Hall et al., 2015; Hart, 2017). Nonetheless, both
humanattitudesandbehaviorsisonepossiblemodulatorofbelief thoseinfavorofandthoseopposingthebraindiseasemodelof
infreewill(VohsandSchooler,2008;VohsandBaumeister,2009; addiction appear to be in agreement about the actual existence
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Racineetal. FreeWillandAddiction
FIGURE1|Impactofneuroscienceinformationofattributionoffreewill.
Neuroscienceinformationonaddictionandattributionoffreewill:Hasnowbeengeneratedasaresultoftheintensificationofresearchactivitiesonthistopicin
neuroscience.Theimplicationsofthisresearchcouldbemanifold,includingforthebasicunderstandingofthemechanismsofaddiction,thedevelopmentof
treatmentaswellaspreventionandpolicy(DackisandO’Brien,2005).
Beliefinfreewillandattributionofresponsibilityinaddiction:Freewillisoftenconsideredapre-conditionofattributionofresponsibilityforone’saddictionandthus
representsanimportantissueinphilosophyandethics(Sinnott-Amstrong,2013).Anemphasisonneuronalcausesofaddictionhasbeenarguedtoremove,inpart,
theonusofresponsibilityoftheindividualbecauseoftheirperceivedorattributedlackofcontrolorfreewillovertheiraddiction(Hyman,2007;Racineetal.,2015).In
contrasttothisbraindiseaseview,the“moralmodel”ofaddictionstressespersonalresponsibilitytowardtheaddictionsuchthatanindividualwithanaddiction
retainsfreewillandpersonalresponsibilityforhis/hercondition(reviewedinRacineetal.,2015).AsHoltonandBerridgesummarize,thetensionbetweentenetsof
braindiseaseandmoralviewssuggeststhat“[t]hetwoapproachesaretypicallyseenasquiteincompatible.Ifaddictionisabraindisease,thenthereisnorolefor
willpowerorself-control”(HoltonandBerridge,2013).
Beliefinfreewillandattributionofstigmainaddiction:Beliefinfreewill–oftenmoreorlessclearlydistinguishedfrombeliefsinresponsibilityintheconceptualand
empiricalliterature(Nadelhofferetal.,2014)couldrelatetostigmaagainstaddictionandthisrepresentsanimportantconcerninpublichealthandanareaofresearch
insocialpsychology.Fiercedebateshavesurfacedabouttheabilityforbiologicalinformationtodiminishresponsibilityandrelatedstigmaintheformofblaming.On
theonehand,attributiontheorypostulatesthatbeliefsaboutsomeone’scontroloverasituationorconditionarerelatedtotheattributionofresponsibilityforthat
situationorcondition(Martinetal.,2000;Corriganetal.,2003).Forexample,ifaperson’sconditionisperceivedascausedbythatperson’sbadcharacter,or“weak
will”,suchasinthecaseofpeerinfluence,thenthecausesoftheconditionareperceivedasbeingunderthatperson’scontrolandthisindividualisdeemed
responsibleforhis/herconditionandtherefore“blaming”couldbeseenas“warranted”.Onthecontrary,ifahealthconditionisperceivedascausedbyagenetic
abnormality,thenthecauseisseenasoutsideofthatperson’scontrolandthereforetheindividualisnotseenasresponsibleforthesituationand“blame”wouldbean
inappropriateresponsetowardsuchaperson.Thiseffecthasbeenunraveledinseveralstudies(Corriganetal.,2003;Dietrichetal.,2006;Sattleretal.,2017).Onthe
otherhand,andinspiteofbeingcommon,theideathatbiologicalinformationreducesattributionoffreewill,andthusdiminishescertaintypesofstigma,remains
contestedwithseveralstudiesreportingresultstothecontrary(WalkerandRead,2002;Phelan,2005;Dietrichetal.,2006;Pescosolido,2013).
Beliefinfreewillandacceptanceoftreatmentinaddiction:Beliefinfreewillandrelatedbeliefsinself-controlcouldsupportattitudesandbehaviorsassociatedwith
seeking(andcomplyingwith)treatmentforaddictionandthisisanissueofimportanceinhealthcareandtreatmentprograms.Biologicalviewsonaddictionwould
facilitatetheuptakeoftreatmentbecausetheindividualwouldnolongerbeconsideredatfaultforhis/herproblem(atleastnottothesameextent)(Dackisand
O’Brien,2005).Also,blamingbecomesfutileforsuchadisease,thuspavingtheway,inprinciple,forgreateracceptanceofmedicaltreatments(Gartneretal.,2012;
Halletal.,2015).However,stressingthebiologicalnatureofaddictionhasnotnecessarilybeenfoundtoencouragetreatment(Gartneretal.,2012)andcouldactually
leadtofatalisticbeliefsthatundercutthemotivationtofollowtreatmentorbeliefsinthecontrolforthetreatmentoftheircondition(VohsandBaumeister,2009).
of an effect of neuroscience information on belief in free will; addiction on belief in free will. One influential study reported
otherwise, the debate would be moot (Holton and Berridge, that(textual)neuroscienceexplanationshavea“seductiveallure”
2013).Addingtothisdebate,braindiseasemodelsofpsychiatric onnaïverespondentsbecausetheyincreasetheattributedvalue
disorderssuchasaddictionareconsideredtobegainingground, of a scientific explanation of psychological phenomena (e.g.,
sometimesattheexpenseofexplanationsbasedonpsychological mutual exclusivity, attentional blink) even if the neuroscience
orsocialfactors(Buchmanetal.,2010). component of the explanation is irrelevant to what is being
explained (Weisberg et al., 2008). This effect was found to
Belief in Free Will and the Seductive Allure
be greater for poor explanations than for good explanations
of Neuroscience Information in the naïve respondents (general adult respondents, although
Interestingly,aliteratureontheseductiveallureofneuroscience the mean age for this group in this study was 20.1 years of
explanations(Weisbergetal.,2008;FarahandHook,2013)and age). Students in a graduate neuroscience course judged both
“neurorealism” (Racine et al., 2005; Rhodes, 2015) has tackled the good and bad explanations as more satisfying when they
the issue of the actual impact of neuroscience on explanations contained irrelevant neuroscience verbiage. However, “experts”
of general psychological phenomena, and could shed light on (a group of those who were either about to pursue, currently
the debate about the impact of the brain disease model of pursuing or already holding advanced degrees in cognitive
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Racineetal. FreeWillandAddiction
neuroscience or cognitive psychology) were not swayed by the neuroimage could be small or smaller when respondents have
addedneuroscienceexplanations(Weisbergetal.,2008). already been swayed by a neuroscience explanation (motivated
Likewise, another landmark study suggested that reasoning), a question that they stress as important to address
neuroimaging evidence bears significant influence on the inthefuture.Atthistime,thedebateabouttheactualeffectsof
explanation of general psychological phenomena (McCabe and textualneuroscienceorneuroimaginginformationisongoing.
Castel, 2008). A first experiment showed that a companion
neuroimagedepictingtheresults,incomparisontoacompanion
bar graph depicting the results, positively influenced the Examining the Impact of Neuroscience
assessmentofthedescriptionoftheresultsandofthescientific Explanations on Belief in Free Will in the
reasoninginthearticle.Asecondexperimentfeaturedacomplex
Context of Addiction
topographical brain image, as the neuroimage could have
The present study seeks to contribute to both debates on
been more persuasive in the first experiment simply because
the perception of free will in the context of addiction and
it was more complex. Neuroimages were found to increase
to the seductive allure of neuroscience information. To shed
the appreciation of the scientific reasoning in comparison to
some light on the debate about belief in free will in the
the topographical brain image. A third experiment featured a
context of the brain disease model of addiction, we used the
genuine news article from the BBC website summarizing data
paradigmatic approaches developed in the literature on the
of a study published in Nature and discussing the potential for
seductive allure of neuroscience. We designed an experimental
neuroimaging-basedliedetection.Theinclusionofaneuroimage
study aimed at understanding the potential influence of
increased values for the adequacy of the conclusion that brain
neuroscienceinformation(bothtextualand/orneuroimaging)on
imaging can be used as a lie detector, but not the evaluation
respondents’attributionoffreewilltoapersonwithanaddiction.
of the adequacy of the title. The inclusion of criticism (for
Theneuroscienceinformationusedinourstudywastakenfrom
half of respondents) had no statistically significant effects
well-trusted and accessible websites (see section Instruments),
for the assessment of the conclusion but diminished the
and is thus information that might currently influence an
assessment of the appropriateness of the title. Taken together,
individual’sbeliefinfreewilloutsideourexperiment.Wechose
the Weisberg et al. and McCabe and Castel studies suggest
to investigate addictions to alcohol and cocaine because they
that neuroscience information could have a seductive allure
are amongst the most common addictions, and have varying
because neuroscience provides a convincing explanation for
effectsonhealthandbehavior(NIDA,20111).Thesesubstances
psychological phenomena. For example, neuroimages could
alsovaryintheirperceivedaddictivenessandpotentiallyimpact
provide “a physical basis for abstract cognitive processes,
freewilldifferently(Jasinskaetal.,2014).Forexample,cocaine,
appealing to people’s affinity for reductionist explanations
an illicit drug, might be seen as leading to stronger addiction
of cognitive phenomena” (McCabe and Castel, 2008). These
thanadruglikealcohol,whichisperceivedaslessaddictiveand
two studies launched further empirical investigations on the
moresociallyacceptableandthusinducesdifferentreactionsand
alleged “seductive allure” of neuroscience information (textual
judgments (Cunningham et al., 1993; Schomerus et al., 2010;
or neuroimaging). Two recent reviews have criticized these
Sorsdahl et al., 2012; Sattler et al., 2017). Specifying the drugs
studiesandtheirfindingsbasedonmethodologicalgroundsand
allowedustomakethequestionsinthesurveylessabstractand
on the lack of confirmation from other similar recent studies
more comprehensible to the reader instead of asking generally
(Farah and Hook, 2013; Michael et al., 2013). Michael et al.
for addiction to substances. It also provided an opportunity to
revieweddataontheimpactofneuroimagesfromaseriesof10
explore the robustness of findings by choosing two substances
experiments with 1,971 respondents, and found no statistically
withdifferentpsychological,physiological,socialeffects,anduser
significant effects in contrast to McCabe and Castel’s original
types.Specialattentionwasgrantedtorespondentcharacteristics
findings. They also found no evidence that education or age
(e.g., gender, age, neuroscience literacy) and their interaction
moderatedtheinfluenceofaneuroimage(Michaeletal.,2013).
with effects associated with neuroscience information. These
The result that neuroimages have no persuasive explanatory
characteristics have not yet been investigated thoroughly so far
powerissomewhatpuzzlingbecauseofpreviousdebates,butthe
in the literature, with a few exceptions (notably Michael et al.,
authorshypothesizedthatperhapsneuroimagesaretootechnical
2013). The focus on addiction and the effects of neuroscience
to bring much additional value to the average reader. Another
informationonfreewillprovidedananchorinacontextwhere
hypothesis is that people have become more skeptical about
there are heated discussions about the impact of the brain
the explanatory power of neuroimages since the McCabe and
disease model of addiction. Based on the research reviewed
Castelstudy(Michaeletal.,2013).Totestthislatterhypothesis,
above,weformulatedthreeprimaryresearchquestions(research
the authors ran a series of five studies focused on the effects of
questions1–3)andtwosecondaryquestions(researchquestions
textual information to replicate the effect found by Weisberg
4–5) stemming from our study design and tackling gaps in the
et al. They found more marked effects of textual neuroscience
literature.
explanations.Toexplainthiseffect,theauthorsrightfullypoint
out that, unlike McCabe and Castel, Weisberg et al. varied the
qualityofthescientificinformationandthatMcCabeandCastel
1NIDA.CommonlyAbusedDrugChart.LastmodifiedJanuary,2016.Available
added a neuroimage to a text already containing neuroscience
online at: http://www.drugabuse.gov/drugs-abuse/commonly-abused-drugs/
explanations. Michael et al. (2013) propose that the effect of a commonly-abused-drugs-chart
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Racineetal. FreeWillandAddiction
Researchquestion1: Doesatextualneurosciencedescriptionof ontherespondents,weexcludedrespondentsthathadtooshort
addictiondiminishattributionsoffreewill exposuretimestothesetreatments2.Consideringtheirexclusion
comparedtoacontrolgroupthatreceived andtheexclusionofcaseswithmissingvaluesofanyinvestigated
nosuchinformation? variable,ouranalysiswasbasedon2,378cases.
Researchquestion2: Do neuroimages referring to addiction Almost60%oftherespondentswerefemale(seeTable1for
diminishattributionsoffreewillcompared descriptive statistics). The average age was approximately 46
toacontrolgroup? yearsandtheaveragenumberofyearsineducation,whichwas
Researchquestion3: Does a combination of a textual basedontwoquestionsoftheGermanMicrocensus(Statistische
neuroscience description and a Ämter des Bundes und der Länder, 2013) was 15 years. Thus,
neuroimage referring to addiction comparedtothegeneralpopulation,oursampleconsistsofmore
yield the strongest diminishing effect on females(52%,informationbasedontheGermanMicrocensus),
attributions of free will compared to a younger individuals (mean age in the general population: 49
controlgroup? years), and those with a higher education (mean years in
Researchquestion4: Do respondents with different educationinthegeneralpopulation:13years).
characteristics(suchasageorneuroscience
literacy) attribute different levels of free Ethics Statement
willtopeoplewithaddiction? The ethics committees of the Institut de recherches cliniques
Researchquestion5: How do such respondent characteristics de Montréal and of McGill University approved the study. All
shape the effect of neuroscience participantsprovidedinformedconsentaboutparticipationand
information on attributions of free datausageconsistentwithCanadianresearchethicsguidance,the
will? Tri-CouncilPolicyStatement(TCPS2).
Instruments
METHODS
Aprofessionaltranslatortranslatedthoseinstrumentsthatwere
Participants and Study Design originally developed in English to German according to the
For our experimental web-based study, we used the “WiSo- procedure described by Brislin (1970). This was followed by a
Panel”(Göritz,2014).Thisopt-inpanelincludes11,517German back-translationbyanotherprofessionaltranslator.Corrections
membersfromallwalksoflife.Membersareregisteredwithbasic were then made after discussing potential differences. To
informationsuchastheirname,e-mail-address,dateofbirth,and test whether respondents understood all the questions, items,
sex.Thus,whileparticipationisnotanonymous,itisvoluntary. and instructions correctly, we ran cognitive pretests (N =
Atanytime,respondentshavetheopportunitytoaskthepanel- 7) with German participants (with various socio-demographic
operator to delete their responses and all respondent data. backgrounds) by using a think-aloud technique and probing
Personal data and responses are stored in different databases. questions, i.e., we encouraged the respondents to think aloud
Names and e-mail-addresses were not matched with responses. whenansweringtheonline-questionnaireandwetherebywanted
On the first page of the questionnaire, respondents were asked identify, for example, questions which seemed to be vague or
to give informed consent about participation and data usage difficult to understand. The insights gained from these pretests
consistent with Canadian research ethics guidance, the Tri- wereusedtorefinetheinstruments.
Council Policy Statement (TCPS2). Secure sockets layer (SSL)
protocolswereusedtoencryptanswersoftherespondentswhile Experimental Treatment
responding.Thee-mailedsurveyrequestexplainedthetopicof To assess the influence of neuroscientific information on
the survey, its length, the field work duration (1 week), and belief about free will of people with addiction, we provided
the voluntariness of participation, and also that an incentive
of 10 loyalty points (worth 1 Euro) would be awarded upon 2Forthisprocedure,wefirstcalculatedthebase-linereadingspeed(BLRS)ofeach
completion—which is a usual payment for this type of study. respondent.Thiswasmeasuredbytheresponsetimetotwoeducationquestions
(highest high school degree and the highest vocational training qualification
Whenapanelmemberreceives50loyaltypoints,theycanrequest
or university/college degree), since they assess simple facts. Generally, those
a transfer of the money to their bank account or donate the
respondents for which a response time could not accurately assessed (i.e.,
moneytothepanel.Byofferingthisreward,wehopedtoincrease respondentswentbackandforthontherelevantquestionnairepages)hadtobe
surveyparticipationanddataquality(Lavrakas,2008;vanVeen excludedfromouranalysis.Furthermore,toreducemeasurementerrorsforthe
etal.,2016). BLRS,measuresbelowthe1percentile(e.g.,responsesoflessthan4s)andthose
Aboutonequarter(26.20%,equalingN=3,018)ofthepanel abovethe99%percentile(e.g.,responsesofmorethan163s)wereexcluded.Then,
(1)eachofthetworesponsetimeswasz-standardized,(2)bothwereaveraged,and
members viewed the first page of the survey. Of these, 94.67%
(3)thismeanscorewasagainz-standardized.
(N =2,857)consentedtoparticipateinthestudyand97.83%of WiththeBLRS,individualexposuretimestoourtreatmentswerepredictedineach
them(N =2,795)completedthesurvey.Overall,thepanelhas treatment.Thispredictedexposuretimewascomparedtotherealexposuretime
an average response rate of 22.5% and average completion rate andrespondents.Ifrespondentswereexposedlessthan33.3%oftheexpectedtime,
theywereexcluded(e.g.,expectedtime37s,butrealexposure10s).Accordingto
of 80%, thus the rates we obtained are slightly higher than the
thatprocedure,29respondentswereidentifiedasbeingtoofastinthetext-only-
averageforstudiesconductedwiththispanel(cf.Göritz,2014).
treatment,38inthetextandneuroimage-treatment,and35intheneuroimage-
Toensurethatourexperimentaltreatmentscouldhaveanimpact only-treatment.
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Racineetal. FreeWillandAddiction
TABLE1|Descriptivestatistics. of the preliminary FAD-4 version. As described above, the
itemsweretranslatedtoGermanandback-translatedtoEnglish,
Mean Standard Min Max
followedbyacognitivepretest.Participantswereaskedtothink
deviation
aboutpeopleaddictedtoeitheralcoholorcocaineandunderthe
ALCOHOL-SUBSAMPLE(N=1,209) influenceoftherespectivesubstanceandtoratetheseitemson
Female −0.58 – 0 1 a6-pointscalerangingfrom“stronglydisagree”[0]to“strongly
Ageinyears 46.53 14.23 16 90 agree”[5].
Educationinyears 15.17 2.63 7 21 We used principal component factor analysis with oblique
Knowledgeaboutneuroscience 2.70 2.29 0 10
oblimin rotation (to allow the factors to correlate) to identify
Alcoholsubstanceusedisorder(SUD) 0.08 – 0 1
thedimensionalityofthescale.TheKaiser-Meyer-OlkinMeasure
Alcoholsubstanceusedisorder(SUD) 0.65 – 0 1
amongpeers of 0.75 for the alcohol-subsample as well as for the cocaine-
Base-linereadingspeed(BLRS) −0.02 0.73 −0.71 8.62 subsample indicated a good suitability of the data for structure
FWRESPONSIBILITY 0.00 1.00 −2.82 1.92 detection. Based on this analysis, a two-factor solution was
FWVOLITION 0.00 1.00 −1.78 3.81 developed: for both subsamples, the items of the originally
COCAINE-SUBSAMPLE(N=1,169)
proposed one factor-solution were separated into a factor
Female 0.57 – 0 1
Ageinyears 46.41 14.40 17 92 focusing on responsibility (FWRESPONSIBILITY; items 1, 2, 3,
Educationinyears 15.17 2.58 8 21 with an eigenvalue above 2.83 for the alcohol subsample and
Knowledgeaboutneuroscience 2.83 2.42 0 10 2.83 for the cocaine subsample) and one focusing on volition
Cocainesubstanceusedisorder 0.01 – 0 1 (FWVOLITION;items4,5,6,and7,withaneigenvalueabove1.15
(SUD)
forthealcoholsubsampleand1.33forthecocainesubsample).
Cocainesubstanceusedisorder 0.09 – 0 1
Duetoasatisfyinginternalconsistencyoftheitemswithineach
(SUD)amongpeers
Base-linereadingspeed(BLRS) −0.01 0.86 −0.71 10.72 ofthesefactors(Cronbach‘sαforFWRESPONSIBILITY:0.78forthe
FWRESPONSIBILITY 0.00 1.00 −2.63 1.77 alcohol subsample and 0.77 for the cocaine subsample; and for
FWVOLITION 0.00 1.00 −1.63 3.60 FWVOLITION: 0.60 for the alcohol subsample and 0.67 for the
N,Numberofobservations. cocaine subsample), we continued our analysis with these two
factors.
the participants with information depicting addiction from a The authors of the scale already mentioned that this scale
neuroscientific point of view. We used three treatments and assesses “assumptions about autonomy” and “declarations that
onecontrolgroup(seeTable2).Thecontrolgroupreceivedno people are responsible for their actions” (Paulhus and Carey,
information. Participants in the text-only-treatment were asked 2011, p. 97). The duality of the scale is also reflected in their
to read thoroughly a brief text extracted from brainfacts.org remarkthat“freewillbeliefsareconsistentwithaninternallocus
(2011)3, a well trusted and accessible website supported by the of control but also include moral responsibility” (Paulhus and
Society of Neuroscience, providing a neuroscience explanation Carey,2011,p.99).Bothfactorsareassumedtobeconditionsfor
ofaddiction.Thetextdisplaysamarkedbiologicalreductionist freewill(LavazzaandInglese,2015).Forthefollowinganalysis,
overtone. The text presented to participants in the text regression factor scores were used for each factor (the score 0
and neuroimage-treatment included an additional neuroimage indicates an average attributed responsibility or volition, and
related to the topic of addiction and the brain also taken 1 is the standard deviation), because usually some items are
from the Internet (from drugabuse.gov; Davis, 2007), from the moreimportantthanotherswhenexplainingacertainconstruct.
website of the National Institute of Drug Abuse. Respondents By using factor scores instead of unweighted sum scores, the
in the neuroimage-only-treatment solely saw the neuroimage. different impacts of each item was accounted for (DiStefano
Presenting the text and the neuroimage independently and et al., 2009). Descriptive results for this and the following two
together allowed us to test whether effects differed for the text instruments are shown in Table1. When describing the results
alone,thepicturealone,ortheircombination.Furthermore,the werefertothetwofactorsasFW andFW ,
RESPONSIBILITY VOLITION
sample was randomly divided in two: one half received follow- whileweusethegenericconceptoffreewilltorefertoliterature
up questions concerning belief in the free will (see below) of thathasnotdifferentiatedbothfactors.
peoplewithanaddictiontoalcohol,andtheotherhalfanswered
questionsfocusingonpeoplewithaddictiontococaine. Self-reportedKnowledgeaboutNeuroscience
Respondents described their overall knowledge about
BeliefinFreeWill neuroscience by responding to the following item: “My
After the experimental treatments (the control group received knowledge of neuroscience in general is...” with an 11-point
no prior information), we assessed belief in free will regarding scalerangingfrom“verylow”[0]to“veryhigh”[10].
peoplewithadrugaddiction.Wethereforeusedsevenadopted
items(seeTable3)oftheFreeWillandDeterminism(FAD-Plus) SubstanceUseDisorder(SUD)
instrument(PaulhusandCarey,2011),whichisanenhancement An adopted version of the ultra-rapid screening for substance-
usedisorders(ASSIST-LITE)(Alietal.,2013)wasusedtoassess
3Brain Facts. Addiction: Introduction. Disease and Disorders. http://www. respondents’ SUD of the two investigated substances, alcohol
brainfacts.org/diseases-disorders/addiction/(AccessedMarch17). and cocaine. Based on this screening, respondents were either
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Racineetal. FreeWillandAddiction
TABLE2|Experimentaldesigna.
Treatment Text Neuroimage Readinginstruction
Control [blank]
Text-only (cid:8) Pleasecarefullyreadthefollowingdefinitionof“addiction”.Thenextpagethen
containsrelatedquestions.Then,pleasepushtheforwardbutton.
Textandneuroimage (cid:8) (cid:8) Pleasecarefullyreadthefollowingdefinitionof“addiction”andcarefullylookat
thepicturedepictinghumans’brainsafterdrugexposure.Thenextpagethen
containsrelatedquestions.Then,pleasepushtheforwardbutton.
Neuroimage-only (cid:8) Pleasecarefullylookatthepicturedepictinghumans’brainsafterdrug
exposure.Thenextpagethencontainsrelatedquestions.Then,pleasepush
theforwardbutton.
Textb WhatisAddiction?
Addictionisachronicbraindiseasethatcausespeopletolosetheirabilitytoresistacraving,despitenegativephysical,personal,orsocial
consequences.Peopleseekoutnicotineandalcohol,orengageingambling,becauseitmakesthemfeelgoodorlessenfeelingsofstressand
sadness.
Manyabuseddrugsproduceapleasurablefeelingbyexcitingcellsinthebrain’srewardcenter.Withrepeateduse,drugscanchangethe
structureofthebrainanditschemicalmakeup[displayedfortextandneuroimage-treatmentonly:(seeexampleinthefigurebelow)].
Butwhycansomepeoplecasuallydrinkalcoholorsmokecigarettes,whileothersfighttokickthehabit?Neuroscienceresearch,bothin
humanandanimalstudies,ishelpingscientistsidentifykeyfactorsthatinfluencesusceptibilitytoaddiction,suchasaperson’sgenetic
makeup,vulnerabilitytostress,andtheagetheystartengaginginthebehavior.
Slowlybutsurely,newstudiesareunravelingcluesaboutprocessesinthebrainthatinfluencethelikelihoodofdrugrelapse.Suchinsightsmay
helpimproverehabilitationprogramsanddrivedowntheglobalcostofaddiction.
Neuroimagec Effectsofdifferentdrugsonthefunctioningofthebrain:Acomparison
betweenthebrainsofnon-addictsandaddicts.
Theadjacentimageshowsthatrepeatedexposuretodrugsdepletesthe
brain’sdopaminereceptors,whicharecriticalforone’sabilitytoexperience
pleasureandreward.
•Indicatesthatthiselementwaspartoftheexperimentaltreatment.
aThesamplewasrandomlyassignedtothesethreeexperimentaltreatmentsorthecontrolgroupdisplayedhere.Furthermore,thesamplewasrandomlydividedintoonegroupasked
aboutthefreewillofpeoplewithaddiction,whileanothergroupweresimilarlyaskedaboutcocaine.
bAdaptedfrom:brainfacts.org(2011),awebsitesupportedbytheSocietyofNeuroscience.
cAdaptedfrom:fromdrugabuse.gov(Davis,2007),thewebsiteoftheNationalInstituteofDrugAbuse.
grouped as no alcohol-SUD (respectively no cocaine-SUD) [0] analcohol-SUD(respectivelyacocaine-SUD)[0]orasknowing
or as having a tendency toward an alcohol-SUD (respectively a peerswithanalcohol-SUD(respectivelyacocaine-SUD)[1].
cocaine-SUD)[1].
Statistical Analyses
SUDamongPeers Our experimental data were analyzed for both subsamples
Furthermore,SUDamongpeerswasassessedbyaskingwhether (alcohol and cocaine) regarding the effects of the experimental
the respondents know anyone who is addicted to the two treatments, self-reported knowledge about addiction, SUD,
substances under investigation (cf. Sorsdahl et al., 2012). and SUD among peers on the FW and the
RESPONSIBILITY
Respondents were either grouped as not knowing anyone with FW .Weusedmultivariateordinaryleastsquares(OLS)
VOLITION
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Racineetal. FreeWillandAddiction
TABLE3|FactoranalysisanddescriptivestatisticsfortheFreeWill(FAD-Plus)items.
Itemsa Alcohol-subsample(N=1,209) Cocaine-subsample(N=1,119)
Factorloading Mean SD Factorloading Mean SD
F1 F2 F1 F2
1.Theymusttakefullresponsibilityforanybadchoicestheymake. −0.84 −0.03 3.29 1.48 −0.84 −0.04 3.39 1.48
2.Inthecaseofcriminals,theyaretotallyresponsibleforthebadthingstheydo. −0.86 −0.02 3.33 1.53 −0.87 −0.00 3.46 1.52
3.Theyarealwaysatfaultfortheirbadbehavior. −0.73 −0.10 2.67 1.55 −0.75 −0.09 2.74 1.49
4.Thesepeoplehavecompletecontroloverthedecisionstheymake.* −0.28 −0.79 0.91 1.19 −0.21 −0.79 1.06 1.28
5.Theycanovercomeanyobstaclesiftheytrulywantto. −0.16 −0.64 1.77 1.19 −0.06 −0.68 1.71 1.47
6.Theyhavecompletefreewill. −0.19 −0.59 1.61 1.50 −0.09 −0.71 1.52 1.42
7.Withthestrengthoftheirmind,theycanalwaysovercometheirbody’scraving −0.35 −0.48 2.05 1.58 −0.25 −0.57 1.81 1.47
for[alcohol/cocaine]b.**
Factorloadingsbasedonprincipalcomponentfactoranalysiswithanobliminrotation(eigenvalues>1)—boldfiguresindicatethehighestloadingofanitem;N,Numberofobservations;
SD,Standarddeviation;F1,FWRESPONSIBILITY;F2,FWVOLITION.
aResponseswereassessedonascalefrom“stronglydisagree”(0)to“stronglyagree”(5).
bDisplayedsubstancereferstothesubstanceinvestigatedfortherespectivesubsamplesforthisitem.
*p<0.01,**p<0.001(differencesbetweenthealcoholandthecocaine-subsamplesbasedont-Tests).
regressionmodelsanddisplayedstandardizedcoefficients(beta) rated that a person addicted to cocaine had lower
and t-values for the main effect models, while unstandardized FW (p=0.039). Age: Older respondents
RESPONSIBILITY
coefficients(alongwitht-values)wereusedforthemodelswith attributed a lower FW to people with addiction
VOLITION
interactions effects. Furthermore, Wald post-estimation tests to alcohol (p = 0.015) as well as to those with cocaine
were used to explore statistical differences between the three addiction (p = 0.016). Education: A greater number of
experimentaltreatments.Wealsocontrolledourresultsforbase- years of education was associated with lower attribution
linereadingspeed(BLRS1)(seefootnote2). of FW in the alcohol- (p = 0.003) and the
RESPONSIBILITY
cocaine-subsamples (p = 0.001) and with a lower attribution
RESULTS of FWVOLITION for people with an addiction to alcohol
(p < 0.001). Self-reported neuroscience-knowledge: Greater
Experimental Treatments (Research self-reported knowledge about neuroscience led to lower
Questions 1, 2, and 3) scores for FWRESPONSIBILITY in the alcohol- (p < 0.001) as
Table4 shows to what extent the experimental treatments well as in the cocaine-subsamples (p = 0.038). SUD: An
influenced respondents’ judgments of free will (which indication for either an alcohol or cocaine SUD had no
was, subsequent to factor analysis, divided in two factors: statistically significant effect on participants’ ratings. Peer
responsibility (FW ) and volition (FW ) SUD: Respondents who reported knowing somebody with
RESPONSIBILITY VOLITION
for people with addiction to alcohol and cocaine. With respect alcohol SUD indicated a lower responsibility in people with
to research questions 1 and 2, we found that respondents’ addiction to alcohol (p = 0.044). BLRS: The BLRS did not
judgments did not significantly differ statistically between the bring any statistically significant effect on the respondents’
control group and the text-only-treatment, nor did they differ evaluations.
significantly between the control group and the neuroimage-
Interaction Effects between Experimental
only-treatment, thus research question 1 and research question
Treatments and Respondent
2 found negative answers. With respect to research question 3,
wedidfindthatacombinationoftextandneuroimageyieldeda Characteristics (Research Question 5)
stronger diminishingeffect,but only for Model 4. Respondents In addition to the main effects analyses, we explored potential
in the text and neuroimage-treatment attributed a moderately interaction effects between our experimental treatments and
lower FWVOLITION (beta = −0.07, p = 0.048) to people with the respondent characteristics (research question 5), thus
an addiction to cocaine. Furthermore, a post-estimation Wald whether any of the respondent characteristics moderate
test showed that those in the image-only-treatment attributed the effects of the treatments. We found no statistically
a lower FWRESPONSIBILITY to people with an addiction to significant interaction effects for sex, gender, education,
alcohol compared to those in the text-only-treatment (p = SUD, peer SUD4, and BRLS. While no statistically significant
0.026). interaction effects occurred between the experimental
Respondent Characteristics (Research
4Oneexceptionisaninteractioneffectbetweenthetextandneuroimage-treatment
Question 4) andpeerSUD(p=0.027),indicatingthatrespondentsknowingpeerswithcocaine
To answer our fourth research question, we examined how SUDhadthelowestattributedFWVOLITIONofpeoplewithaddictiontococaine.
Duetothesingularityofthisinteractionandgiventherelativelylowprevalenceof
several respondent characteristics related to FW
RESPONSIBILITY peerSUD,wedonotfurtherdiscussthisfinding,butweencourageforthcoming
and FWVOLITION. Gender: In comparison to men, women researchtodoso.
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TABLE4|LinearregressionmodelsoftheFWRESPONSIBILITYandFWVOLITIONregardingpeoplewithaddictiontoalcoholorcocaineonexperimentaltreatmentsand
respondentcharacteristics.
Alcohol-subsample Cocaine-subsample
Model1 Model2 Model3 Model4
FWRESPONSIBILITY FWVOLITION FWRESPONSIBILITY FWVOLITION
beta t-value beta t-value beta t-value beta t-value
EXPERIMENTALTREATMENTS(REF.=CONTROLGROUPTHATRECEIVEDNOADDITIONALINFORMATION)
Text-only −0.06 −1.75 −0.02 −0.58 −0.05 −1.32 −0.06 −1.82
Textandneuroimage 0.00 0.05 0.05 1.36 −0.01 −0.24 −0.07* −1.98
Neuroimage-only 0.02 0.53 0.02 0.51 −0.02 −0.44 −0.04 −1.17
RESPONDENTCHARACTERISTICS
Female 0.02 0.55 −0.04 −1.37 −0.06* −2.07 −0.04 −1.19
Ageinyears 0.03 1.08 −0.07* −2.44 −0.04 −1.18 −0.07* −2.41
Educationinyears −0.09** −3.03 −0.13*** −4.40 −0.10*** −3.36 −0.04 −1.40
Neuroscience-knowledge −0.12*** −4.11 0.03 0.99 −0.06* −2.08 0.06 1.87
SUDa −0.02 −0.72 −0.03 −0.92 −0.04 −1.31 0.02 0.66
SUDamongpeersa −0.06* −2.02 0.00 −0.04 0.00 −0.08 0.04 1.29
BLRS 0.01 0.46 0.00 0.15 0.02 0.75 0.04 1.36
Intercept 0.63** 2.91 0.98*** 4.48 0.90*** 4.03 0.54* 2.41
Observations 1,209 1,209 1,169 1,169
AdjustedR2 0.03 0.01 0.01 0.01
F 4.89 2.81 2.63 2.13
Probability>F 0.00 0.00 0.00 0.02
Beta,standardizedcoefficients.
aForthealcoholsubsample,thismeasurereferstoanSUDregardingalcohol,whileitreferstoSUDregardingcocaineforthecocainesubsample.
*p<0.05,**p<0.01,***p<0.001.
treatments and neuroscience-knowledge with regard to the perceived FW of people with addiction to alcohol
VOLITION
attributed FW of people with addiction to (p=0.035)5.
RESPONSIBILITY
alcohol (see Model 1 in Table5 and Panel A in Figure2),
several interactions between these variables occurred for FWVOLITION AttributionsRegardingPeoplewith
the three other dependent variables (FWVOLITION−alcohol, AddictiontoCocaine
FWRESPONSIBILITY−cocaine,andFWVOLITION−cocaine)(seeModels No statistically significant overall effect for neuroscience-
2–4inTable5andPanelB-DinFigure2)whicharedescribed knowledge was found in the model on FWVOLITION of people
below. with addiction to cocaine without the interaction effects—
as is visible in Table4. Nonetheless, Model 4 in Table5
(see also Panel D in Figure2) show that, in the control
FWVOLITION AttributionsRegardingPeoplewith group, increasing neuroscience-knowledge resulted in a higher
AddictiontoAlcohol attribution of FW to people with addiction to cocaine
VOLITION
As shown in Table4, no statistically significant main effects (p<0.001).Thiseffectofneuroscience-knowledgesignificantly
for neuroscience knowledge and the experimental treatment differedfortheotherthreeexperimentaltreatments,i.e.,forthe
were found on the perceived FWVOLITION of people with text-only-treatment (p = 0.001) and the image-only-treatment
addiction to alcohol. However, we also saw that neuroscience- (p = 0.007) the respective lines were almost parallel to
knowledge had an effect in the control group (see Model 2 in
Table5).Specifically,increasedneuroscience-knowledgeslightly 5As our interaction analyses do not allow a clear interpretation whether
augmented (p = 0.036) the attributed FW of people neuroscience-knowledge moderates the effect of the experimental treatments
VOLITION
withaddictiontoalcohol(seeascendingdottedgraylineinPanel or whether the experimental treatments moderates the effect of neuroscience-
knowledge,thisandthefollowingpresentationoftheinteractionseffectscould
B in Figure2). However, increasing neuroscience-knowledge
also be reversely described, e.g., this interaction effect could be also described
resultedinanoppositepatternintheneuroimage-only-treatment:
as:PresentinganeuroimageresultsinalowerattributedFWVOLITIONregarding
here, increasing neuroscience-knowledge led to slightly lower peoplewithaddictiontoalcoholwithincreasingneuroscience-knowledge.
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Racineetal. FreeWillandAddiction
TABLE5|LinearregressionmodelsoftheFWRESPONSIBILITYandFWVOLITIONregardingpeoplewithaddictiontoalcoholorcocaineonexperimentaltreatmentsand
respondentcharacteristics.
Alcohol–subsample Cocaine–subsample
Model1 Model2 Model3 Model4
FWRESPONSIBILITY FWVOLITION FWRESPONSIBILITY FWVOLITION
B-value t-value B-value t-value B-value t-value B-value t-value
EXPERIMENTALTREATMENTS(REF.=CONTROLGROUPTHATRECEIVEDNOADDITIONALINFORMATION)
Text-only 0.04 0.34 0.07 0.57 −0.09 −0.69 0.17 1.37
Textandneuroimage 0.09 0.72 0.22 1.76 0.02 0.12 0.25 1.93
Neuroimage-only 0.09 0.72 0.24 1.95 0.19 1.50 0.17 1.29
RESPONDENTCHARACTERISTICS
Female 0.04 0.62 −0.08 −1.39 −0.12*** −2.02 −0.07 −1.14
Ageinyears 0.00 1.07 −0.01*** −2.48 0.00 −1.26 0.00* −2.15
Educationinyears −0.03** −3.06 −0.05*** −4.41 −0.04*** −3.48 −0.01 −1.22
Neuroscience-knowledge −0.02 −0.96 0.05* 2.10 0.00 −0.06 0.11*** 4.53
SUDa −0.07 −0.70 −0.10 −0.94 −0.44 −1.36 0.21 0.65
SUDamongpeersa −0.12* −2.02 0.00 0.07 0.01 0.07 0.13 1.25
BLRS 0.02 0.46 0.01 0.19 0.02 0.68 0.05 1.52
INTERACTIONSBETWEENEXPERIMENTALTREATMENTSANDNEUROSCIENCE-KNOWLEDGE(NK)
Text-only*NK −0.07 −1.88 −0.04 −1.25 −0.01 −0.24 −0.12*** −3.37
Textandneuroimage*NK −0.03 −0.92 −0.04 −1.16 −0.01 −0.35 −0.15*** −4.15
Neuroimage-only*NK −0.02 −0.50 −0.07* −2.12 −0.08* −2.27 −0.09** −2.69
Intercept 0.56* 2.50 0.88*** 3.88 0.86*** 3.67 0.24 −1.01
Observations 1,209 1,209 1,169 1,169
AdjustedR2 0.03 0.01 0.01 0.01
F 4.89 2.81 2.63 2.13
Probability>F 0.00 0.00 0.00 0.02
B-Value,unstandardizedcoefficients;NK,Neuroscience-knowledge.
aForthealcoholsubsample,thismeasurereferstoanSUDregardingalcohol,whileitreferstoSUDregardingcocaineforthecocainesubsample.
*p<0.05,**p<0.01,***p<0.001.
the x-axis, indicating no moderating effect of neuroscience- those respondents with the lowest value of neuroscience-
knowledge, and for the text and neuroimage-treatment an knowledge, the attributed FW was significantly
RESPONSIBILITY
increase in neuroscience-knowledge slightly decreased the higher in the neuroimage-only-treatment compared to the
attributed FW of people with addiction to cocaine text-only-treatment(p=0.030).
VOLITION
(p<0.001).
DISCUSSION
FW AttributionsRegardingPeoplewith
RESPONSIBILITY
AddictiontoCocaine Weembarkedonanexperimentalstudytotestiftheattribution
In Table4, we reported a negative main effect of neuroscience offreewill(whichwas,subsequenttofactoranalysis,dividedin
knowledge on the attributed FW of people with twofactors:FW andFW )topeoplewitha
RESPONSIBILITY VOLITION RESPONSIBLITY
an addiction to cocaine. As Model 3 in Table5 and Panel drugaddictionwasdiminishedbyshowingrespondentsatextual
C in Figure2 show, by analyzing the interaction between neuroscience description of addiction (research question 1), a
neuroscience-knowledge and the experimental treatments, neuroimagesuggestingabiologicalbasisforaddiction(research
we found that increasing neuroscience-knowledge reduced question 2), or both (research question 3) in comparison to a
FW only for the neuroimage-only-treatment (p controlgroup.Bothpromptsweretakenfrompubliclyavailable
RESPONSIBILITY
= 0.023). This interaction effect significantly differed from sources to increase their relevance and ecological validity. To
the interaction effect between neuroscience-knowledge and answeroursecondaryresearchquestions,wealsoassessedhow
text-only-treatment(confirmedbyapost-estimationWaldtest,p respondentcharacteristicsaffectedfreewillattribution(research
=0.036):theresultsshowthatnostatisticallysignificanteffectof question4)aswellashowthesecharacteristicsinteractedwiththe
neuroscience-knowledge was found for the text-only-treatment. experimental treatments regarding these attributions (research
However, a post-estimation Wald test also indicated that for question5).
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