in milgram s classic experiments on obedience [ 1 , 2 ] , an experimenter ordered volunteer participants to inflict allegedly painful shocks to a third party . these studies focused on participants readiness to conform to authority and obey coercive instructions to perform harmful actions . interestingly , participants subjective experience in such situations has not been systematically investigated , even though the legal defense of  only obeying orders  implies a loss of voluntary agency with coercion . sense of agency refers to the subjective experience of controlling one s actions , and , through them , external events . explicit reports of perceived agency are modulated by numerous biases , notably social desirability and cognitive dissonance effects . for example , individuals coerced into harmful actions might report reduced sense of agency for secondary gain , such as avoiding blame or punishment . implicit measures may provide more direct access to the cognitive mechanisms underlying sense of agency , since these measures are less affected by task demands and social factors such as desirability . here we used the perceived compression of time between a voluntary action and its outcome   as an appropriate implicit marker of sense of agency , and we investigated how coercion influenced this measure . action - outcome intervals are perceived as shorter for intentional actions than for unintended actions such as passive movements [ 5 , 6 ] . therefore , if coercion indeed reduces the core experience of agency , interval estimates should be longer in the coercive than in the free - choice condition . in a first experiment , participants were tested in pairs . in a first group of participants , the agent could freely choose on each trial to increase her own remuneration by taking money from the  victim  ( financial harm ) . in a second , smaller group , the agent could freely choose to administer an electric shock to the  victim  ( physical pain ) , again increasing her own remuneration . this free - choice condition was compared to a coercive condition , in which the experimenter stood next to the agent and ordered her before each trial whether to take money or not , or whether to shock the no participants withdrew from the experiment , and none reported any distress either after testing or at follow - up . in the financial harm group , agents freely chose to take money from the  victim  in 33.97/60 trials ( 95% confidence interval [ ci ]  = 29.0738.88 , min 0 , max 60 ) . in the physical pain group , agents freely chose to give painful electric shocks to the  victim  in 31.37/60 trials ( 95% ci  = 24.9637.78 , min 6 , max 60 ) . in addition , our free - choice condition captured key features of interpersonal choice , such as social reciprocity . in particular , experiencing pain as a  victim  guided subsequent free choices whether to inflict pain on one s co - participant . victims  and then agents , participants who initially received high numbers of shocks as  victim  subsequently gave more shocks ( t(9 )  = 4.776 , p  = 0.001 , r  = 0.860 ) . we analyzed agents interval estimates using anova , with condition ( free choice , coercive ) and outcome ( harm , no harm ) as within - subject factors , and group ( financial harm , physical pain ) as a between - subjects factor . the main effect of condition was significant ( f(1,50 )  = 22.740 , p  < 0.001 , partial  = 0.313 ) , with coercion leading to longer interval estimates than free choice ( 437  ms , 95% ci  = 399475 , and 370  ms , 95% ci  =  338402 , respectively ; see figure  4 ) . there was a main effect of group , with lower interval estimates for the financial harm group than for the physical pain group ( f(1,50 )  = 6.042 , p  = 0.017 , partial  = 0.108 ) but no evidence for any interaction between group and condition ( f(1,50 )  = 0.073 , ns ) . the interaction condition  outcome was not significant ( p  = 0.099 ; for full anova table and further results , see the supplemental experimental procedures ) . interestingly , there was a significant interaction between outcome and group ( f(1,50 )  = 6.201 , p  < 0.02 , partial  = 0.110 ) . in the financial harm group , interval estimates decreased on trials when participants actually delivered harm ( 352  ms , 95% ci  = 316388 ) compared to when they did not ( 375  ms , 95% ci  = 336414 ; t(34 )  = 2.699 , p  = 0.01 , cohen s d  = 0.456 ) . however , in the physical pain group , this difference was not significant ( p > 0.2 ) . importantly , there was no three - way interaction with choice condition  so we found no evidence that sense of agency varied specifically as a function of freely chosen outcomes . the effect of coercion was thus not related to whether or not agents delivered harm on any specific trial or to the content of any individual instruction , but was rather a contextual effect of receiving coercive instructions . this result also rules out explanations based on the attentional or arousing effects of harming others leading to altered time perception . data for one participant in the active control condition was not available because of technical problems during testing . planned comparisons showed that the free - choice condition produced shorter interval estimates than the active control condition ( t(56 )  = 2.809 , p  = 0.007 , cohen s d  = 0.372 ) . conversely , the coercive condition did not differ significantly from the passive condition ( p > 0.6 ) . these results suggest that voluntary actions made under coercion are experienced in some ways as if they were passive . because participants free choices varied , we investigated whether any difference between free - choice and coercive conditions could simply reflect differences between these conditions in the number of harmful actions . we therefore added the difference between the number of harmful actions freely chosen by each participant and the number ordered by the coercive experimenter as a covariate . the covariate was not significant ( p > 0.7 ) , and the overall pattern of conclusions remained unchanged . thus , our results reflect a specific effect of coercive instruction on the subjective experience of agency , occurring at the moment of voluntary action , rather than any difference between the contents of coercive instruction and free choices . in summary , when the agent was coerced , they experienced less agency than when they freely chose between the same options . this difference between coercion and choice did not interact with whether harm was actually inflicted or not . pre - session questionnaire responses allowed us to investigate whether sense of agency under coercion could be related to personality or trait empathy [ 8 , 9 ] . we therefore explored whether personality and empathy measures were related to the  harm effect , i.e. , the main effect difference between interval estimates associated with harmful actions and interval estimates associated with non - harmful actions . questionnaire scores of trait empathy were positively and significantly related to the extent to which a harmful outcome event reduced participants individual agency estimates ( table s1 ) . more empathetic individuals showed a more dramatic reduction in sense of agency when their actions had harmful outcomes , compared to less harmful outcomes . correlations with personality factors were generally weaker . additionally , we investigated whether the coercion effect , corresponding to the main effect difference between interval estimates associated with the coercive condition and interval estimates associated with the free - choice condition , correlated with personality and trait empathy ( table s2 ) . the experience of agency under coercion has been surprisingly neglected in previous discussions , despite its obvious relation to personal responsibility . here , we observed that being ordered to perform an action reduces the subjective experience of agency over the outcome in comparison with being free to choose between outcomes , as shown by reduced estimates of the temporal interval between action and outcome . crucially , the effect of coercion was not related to whether harm actually occurred on any specific trial or to the content of any individual instruction ( financial loss versus painful shock ) , but was rather a contextual effect of receiving coercive instructions . sense of agency was previously shown to increase with the size of the  response space  of action choices . a similar cognitive mechanism may explain why coercion both reduces the basic experience of agency and simultaneously increases compliance with instructions .  only obeying orders  may not merely be a retrospective narrative of behavior , aimed at secondary gain such as blame avoidance , but may rather reflect a genuine difference in subjective experience of agency . coercive instructions appear to induce a passive mode of processing in the brain compared to free choice between alternatives . in a second experiment , we investigated whether coercion changes brain activity , by focusing on electroencephalogram ( eeg ) potentials evoked by action outcomes . filevich and colleagues   showed greater event - related potential ( erp ) amplitudes for outcomes when participants freely chose an action compared with being instructed . we therefore predicted that coercive instructions should reduce outcome - evoked erp amplitudes relative to free choices . no participants withdrew from the experiment , and none reported any distress either after testing or at follow - up . agents freely chose to administer painful electric shocks to the  victim  in 18.75/60 trials ( 95% ci  = 11.4626.04 , min 0 , max 52 ) . regression analysis again showed modest support for vindictive behavior , as in experiment 1 , with a trend for participants who served first as victims  tending to choose to administer shocks in proportion to the number they had previously received ( t(9 )  = 1.681 , p  = 0.1 , r  = 0.561 ) . we also assessed how responsible participants felt during each condition by asking them to rate , in a post - session questionnaire , their responsibility as a percentage score in each condition . as expected , participants reported a higher degree of responsibility in the active condition ( 56.15% , sd  = 39.70 ) than in the passive condition ( 17.92% , sd  = 24.12 ; t(19 )  = 3.792 , p  = 0.001 , cohen s d  = 0.847 ) . interestingly , they also reported feeling more responsible in the free - choice condition ( 86.85% , sd  = 16.31 ) than in the coercive condition ( 34.80% , sd  = 22.53 ; t(19 )  = 9.832 , p  < 0.001 , cohen s d  = 2.19 ) , but also than the active control condition ( 56.15% , sd  = 39.70 ; t(19 )  = 3.562 , p  = 0.002 , cohen s d  = 0.796 ) . in addition , the degree of responsibility was higher in the coercive condition ( 34.80% , sd  = 22.53 ) than in the passive control condition ( 17.92% , sd  = 24.12 ; t(19 )  = 2.699 , p  = 0.014 , cohen s d  = 0.603 ; see figure  3 ) . agents interval estimates were analyzed using repeated - measures anova , with condition ( free choice , coercive ) and outcome ( harm , no harm ) as within - subject factors . the main effect of condition was significant ( f(1,16 )  = 15.123 , p  = 0.001 , partial  = 0.486 ) , with free choice producing shorter interval judgments than coercion ( 366  ms , 95% ci  = 288444 , and 424.5  ms , 95% ci  = 351498 , respectively ; see figure  4 ) . the main effect of outcome was not significant ( p > 0.8 ) , nor was the interaction condition  outcome ( p > 0.5 , for a full anova table and further results , see the supplemental experimental procedures ) . planned comparisons with our control conditions showed that the passive and the coercive conditions did not differ ( p > 0.9 ) and that the free - choice condition did not differ from the active condition ( p > 0.09 ) . standard erp recording and processing methods were used ( see the supplemental experimental procedures ) . we applied repeated - measures anova to the auditory n1 amplitude , with the same anova design used for interval estimates . the main effect of condition was significant ( f(1,16 )  = 8.009 , p  = 0.012 , partial  = 0.334 ) , with free choice producing more negative n1 amplitudes than coercion ( 10.70  v , 95% ci  = 13.81 to 7.60 , and 8.15  v , 95% ci  = 10.83 to 5.47 , respectively ) . the main effect of outcome was not significant ( p > 0.1 ) , nor was the interaction condition  outcome ( p > 0.4 ; for a full anova table and further results , see the supplemental experimental procedures ; see figure  5 ) . interestingly , comparison between our active and passive control conditions showed a similar , but smaller , effect . specifically , n1 amplitude was reduced in the passive condition ( 9.99  v , sd  = 4.39 ) relative to the active condition ( 11.11  v , sd  = 3.76 ; t(19 )  = 1.814 , p  = 0.086 , cohen s d  = 0.405 ; see figure  6 ) . thus , the psychological effect of coercion on sensory processing was similar to the physiological effect of subtracting voluntary motor commands from bodily movement . further , a direct comparison between the free - coercive difference , and the active - passive difference , expressed as the interaction term of a 2   2 anova , showed that the modulation of sensory processing due to coercion was significantly stronger than the modulation by the voluntary motor command ( f(1,17 )  = 4.878 , p  = 0.041 , partial  = 0.223 ) . direct planned comparisons between experimental and control conditions showed that the free - choice experimental condition did not differ from the active control condition ( p > 0.6 ) . the auditory n1 was more pronounced in the passive condition ( 9.99  v , sd  = 4.39 ) than in the coercive condition ( 7.93  v , sd  = 4.85 ; t(19 )  = 3.377 , p  = 0.003 , cohen s d  = 0.755 ) . receiving coercive orders again reduced the sense of agency over potentially harmful actions , according to our implicit measure based on intentional binding . again , coercion produced an experience that more closely resembled passive movement than freely chosen voluntary action . this effect was again linked to the context of coercive instruction , rather than the actual harm resulting from any particular action . coercive orders thus influenced both explicit judgments of agency and the low - level subjective feeling of agency on which such judgments may be based . the defense of  only obeying orders  is often treated with suspicion in law because of the clear secondary gain associated with denying responsibility . however , our result suggests that primary feelings and neurophysiological processing of agency are indeed reduced by coercion . analysis of the auditory n1 amplitude showed that coercion reduced processing of action outcomes compared to conditions in which participants freely chose what action to perform . this finding was again independent of whether the tone was accompanied by a painful electric shock to the co - participant or not . we suggest that coercive contexts produce an anticipatory reduction of sensory processing for action outcomes . indeed , the passive condition also displayed a reduction of the auditory n1 amplitude in comparison with the active condition , suggesting that the brain may treat consequences of one s actions under coercion as if they were passively triggered . interestingly , we found no evidence for sensorimotor attenuation of outcome processing [ 14 , 17 ] when comparing either active versus passive movements or free versus coerced actions . however , the outcomes in our study occurred later than the short post - action window within which sensorimotor attenuation operates . issues of personal responsibility , moral action , and social influence are central to many accounts about human nature . previous behavioral experiments have studied these issues using laboratory experiments . however , the design and interpretation of those studies have been criticized . for example , milgram s participants did not actually deliver pain , and pain responses of the third party were faked by an actor . it remains unclear whether milgram s participants really believed they were delivering severe pain or whether they had some intuition that they were part of a simulation . in our design , participants acted reciprocally as agent and  victim ,  both delivering and receiving harm . they knew from direct sensory experience how their actions would affect their co - participant . moreover , the combination of money and pain in our experiments ensured that our participants were motivated by greed and fear , factors that may pervasively influence many human choices . legal , historical , and psychological   thought have all considered how obeying orders influences personal responsibility . social constructs , including power   and authority , are often invoked . using an implicit marker of sense of agency based on time perception , we showed that coercive instructions caused participants to experience less agency over the harmful outcomes of their actions . the results generalized over implicit and explicit measures of agency , and also over financial harm and physical pain , and they were also found on subsets of trials where no harm was actually delivered . our results suggest that  only obeying orders  may not merely be a retrospective narrative of behavior , adopted for secondary gain such as mitigation , but may rather reflect a genuine difference in subjective experience of agency at the point of action itself . a previous study   reported that sense of agency decreased as the size of the  response space    or alternative actions decreased . we suggest that this cognitive mechanism may also underlie the effects of coercion on sense of agency reported here . interestingly , our effects of coercion on sense of agency were quite general across individuals and were not strongly associated with particular personality traits or with empathy . this was not merely due to insensitivity of agency measures , since the effects of harm versus non - harm on sense of agency were higher in those with more empathic traits , as might be predicted . rather , our result clearly suggests one reason why so many people can be coerced . specifically , coercion may reduce the linkage that normally binds the experience of actions to their outcomes . indeed , emotional distancing from distasteful outcomes of one s own necessary actions forms a specific part of training and professional culture in medicine   and in the military . training effects might also work in the opposite direction : learning the true valence of one s actions outcomes might potentially make the sense of agency more resilient to the undermining effects of coercion . we showed that acting under coercion deeply modifies the sense of being responsible for outcomes of one s actions . both results can be interpreted as a cognitive operation of  distancing ,  or reducing the linkage between one s own decision - making , action , and outcome . our finding of reduced experience of agency under coercion does not legitimate nuremberg - type defenses : society could still expect agents to try to resist evil [ 10 , 24 ] . however , our results do suggest that people may indeed experience reduced agency at the point of being coerced to perform abhorrent actions . clearly , society needs protection from harm , irrespective of whether the perpetrators experienced agency at the time of the act , or not . for example , the law argues that informed , rational agents should know they remain responsible for their actions , even if they have minimal experience of agency at the time of action . further , the law could shift its focus away from those who obey orders toward those who give them , to prevent them from abusing a position that allows them to coerce others . our research on the experience of agency highlights the fundamental link between law and cognitive neuroscience . the law has to engage with the human capacity to control action if it is to fulfil its function of allowing individuals to live together in societies . no participant withdrew , and no participant reported distress at debriefing or at later follow - up . only female participants were tested in order to control for potential effects of gender , both within the participant pairs , and also between participants and the ( female ) experimenters . data from a number of standard questionnaires , including big five personality and trait empathy , were available from collection prior to participation . the protocol for matching participants in pairs stipulated that participants could not be relatives , friends , or from the same course or faculty . thus , there was no particular relation between co - participants prior to the experiment . data exclusion criteria were decided in advance of the experiment : failure to produce temporal intervals covarying monotonically with actual action - tone interval and any general failure to follow instructions . to identify participants for whom the action - tone intervals did not gradually increase with action - tone intervals , we performed linear trend analyses with contrast coefficients 1 , 0 , 1 for the three delays of the action - tone intervals ( see the next section ) . after this procedure , 39 participants remained in group 1 ( mean age  = 22.92 , sd  = 3.82 ) and 19 in group 2 ( mean age  = 22.79 , sd  = 3.63 ) . on arrival at the experimental laboratory , participants read an information sheet about the experimental procedure and the aim of the experiment . the two co - participants signed their individual consent forms simultaneously , ensuring that they were both aware of the other s consent . roles were assigned randomly so that one of the participants was told they were the agent and the other was the  victim . these roles were reversed for the second half of the experiment , making the procedure fully reciprocal . an external , silent sodial flexible foldable usb keyboard was placed between them , oriented toward the agent but visible to both . the experimental task ran on a computer , which was located on the agent s right side with the screen visible only to the agent ( see figure  2 ) . the agent was instructed to press a key on the keyboard at a time she chose after the start of the trial , using the right index finger . the delay between key press and tone was set to vary randomly between 200 , 500 , and 800  ms . the participants task was to estimate the delay between the key press and the tone . they were informed that the delay would vary randomly on a trial - by - trial basis , between 0 and 1,000  ms ( they were reminded that 1,000  ms makes 1 s ) . participants were also told to make use of all possible numbers between 1 and 1,000 , as appropriate , avoiding restricting their answer space ( e.g. , not only use numbers between 1 and 100 ) , and avoiding rounding ( cf . ) . each participant received a paper sheet with 60 empty boxes for their time estimates in each condition of the task . participants answers were hidden from view of the other participant by a barrier , so as to avoid participants being biased by the other participant s answers . the agent pressed the space key whenever she wanted . in the passive control condition , the experimenter pressed the agent s index finger down on the space bar , making sure to be unpredictable in her movements so as to minimize motor preparation in the agent . during these conditions participants were informed that they would both start with a specific amount of money ( i.e. ,  20 for group 1 and  15 for group 2 ; this difference was due to the fact that participants in group 1 could lose money , but we needed to make sure participants would leave the experiment with the mandated minimum payment of  7.50/hr ) . in the free - choice condition , agents were instructed that they could freely choose to increase their remuneration for the experiment by delivering , or not delivering , a financial harm ( group 1 ) or a physical pain ( group 2 ) to the other participant , using the appropriate keys on the keyboard . the computer screen displayed which key press would be associated with which action ( for instance , the  f  key for taking money / delivering a shock and the  h  key for refraining from taking money / delivering a shock ) . in group 1 , the agents earned 5p each time they chose to inflict financial pain to the  victim ,  who then lost 5p . in group 2 , the agents earned 5p each time they decided to deliver a painful electric shock to the  victim . they earned no money if they decided not to deliver a shock . during this condition , the experimenters did not look at the participants , but focused their attention on task irrelevant objects . in the coercive condition , the experimenters stood up next to the agent and ordered her , on each trial , to take money or not ( group 1 ) or to administer a shock or not ( group 2 ) to the  victim . the tone played after the key press was the same for both keys . in group 1 , did not know on each trial whether the agent had chosen to inflict financial harm or not and did not know which of the agent s response keys was mapped to financial harm  this information was available only on the agent s feedback display screen . l  ) were used when roles were reversed in group 1 , so that former victims  could not now simply repeat harm done to them by repeating the agent s previous key presses . thus , group 1 was prevented from imitative behavior . in group 2 , participants inevitably experienced the action selected by the agent on each trial , in the form of physical pain . therefore , imitative behavior would become unavoidable : we thus decided to use the same key - press mappings throughout . the gains and losses were displayed on the screen visible to the agent . in group 1 , the agent saw two moneybags , 1 with her own money and 1 with the  victim s  money . each time the agent inflicted financial harm , a coin was shown moving from the  victim s  bag to her bag , and the total amount of money increase was displayed . when the agent did not take money , no animations were displayed . in group 2 , the agent only saw her own moneybag on the screen since the  victim  did not lose money , but instead received a painful shock to their left hand . the shock caused a twitch of the  victim s  hand that was readily visible to the agent . this variation allowed some control over possible effects of experimenter s nastiness on participants behavior and experiences under coercion . in group 2 , both experimenters were simultaneously present , but one gave the coercive instructions . both experimenters instructed agents to deliver shocks 30/60 times . participants performed the active or the passive control condition first , then the free - choice condition , then the coercive condition , and then the remaining control condition , either active or passive . we chose not to randomize free - choice and coercive conditions in order not to bias participants in the free - choice condition from previous experience in the coercive condition ( e.g. , attempting to match the coercive experimenter s instructions in their  free participants went through the same four conditions twice , once as agent and once as  victim ,  that is , eight conditions in total . there were 60 trials per condition ( 20 trials at each action - tone delay , in randomized order ) , giving a total of 480 trials . details of the painful stimulation and other measures are given in the supplemental experimental procedures . at the end of the experiment , participants were paid separately based on their earned financial gain during the experiment . for one dyad in group 1 , the experimenter judged that the relation between the agent and the  victim  had become conflictual and hostile . the experimenter made an on - the - spot decision to pay both of these participants the same amount (  20 ) , to reduce the possibility of subsequent distress or conflict . the study was approved by the ethical committee of the universit libre de bruxelles ( 018/2015 ) . no participant withdrew , and no participant reported distress at debriefing or at later follow - up . twenty - two right - handed student female participants were recruited in pairs and paid  2531 for their participation . the same protocol for matching participants and the same data exclusion criteria than in experiment 1 two participants were excluded because no relation was found between perceived and actual action - shock intervals . after this procedure , 20 participants remained ( mean age  = 23.15 , sd  = 3.183 ) . we used the same method as for the physical pain group in experiment 1 , with modifications for eeg recording . participants were instructed to wait a minimum of 2  s in a relaxed position before pressing a key , so as to obtain a consistent and noise - free baseline . participants were further instructed not to move for up to 2  s after the tone . participants first performed 30 trials in the active and the passive conditions , then 60 trials in the two experimental conditions , and then again 30 trials in the active and the passive conditions . these combinations of conditions were counterbalanced across participants . in order to have the same number of choices between the control and the experimental conditions , participants could choose between pressing the agent was asked to position two fingers ( the index finger and the middle finger ) on the two keys and the experimenter pressed down on one of the agent s fingers at an unpredictable moment in time . in the post - session questionnaire , we additionally asked participants to rate ( from 0 ,  not responsible at all ,  to 100 ,  entirely responsible  ) how much they felt responsible in each condition . we also asked participants to rate how frequently they would have disobeyed if they could have ( from 3 ,  almost never ,  to  + 3 ,  almost all the time  ) . in this experiment , the mean stimulation level selected by this procedure was 18.3 ma ( sd  = 6.7 , pulse duration  = 200  s ) . the behavioral data reported in this paper have been published in mendeley data and are available at http://dx.doi.org/10.17632/322y43x9b7.1 .
summarypeople may deny responsibility for negative consequences of their actions by claiming that they were  only obeying orders .  the  nuremberg defense  offers one extreme example , though it is often dismissed as merely an attempt to avoid responsibility . 
 milgram s classic laboratory studies reported widespread obedience to an instruction to harm , suggesting that social coercion may alter mechanisms of voluntary agency , and hence abolish the normal experience of being in control of one s own actions . 
 however , milgram s and other studies relied on dissembling and on explicit measures of agency , which are known to be biased by social norms . here , we combined coercive instructions to administer harm to a co - participant , with implicit measures of sense of agency , based on perceived compression of time intervals between voluntary actions and their outcomes , and with electrophysiological recordings . in two experiments , 
 an experimenter ordered a volunteer to make a key - press action that caused either financial penalty or demonstrably painful electric shock to their co - participant , thereby increasing their own financial gain . 
 coercion increased the perceived interval between action and outcome , relative to a situation where participants freely chose to inflict the same harms . 
 interestingly , coercion also reduced the neural processing of the outcomes of one s own action . 
 thus , people who obey orders may subjectively experience their actions as closer to passive movements than fully voluntary actions . 
 our results highlight the complex relation between the brain mechanisms that generate the subjective experience of voluntary actions and social constructs , such as responsibility .