Improvement in Deception Detection under Stress. Mike R. J. van der Burgt. Accompanied by Anna E. van t Veer. Tilburg University

Transcription

1 1 Improvement in Deception Detection under Stress Mike R. J. van der Burgt Accompanied by Anna E. van t Veer Tilburg University

2 Abstract 2 In this study we investigated whether anticipatory stress enhances deception detection when asked directly and indirectly through perceived trustworthiness. The hypothesis of the study was that anticipatory stress would enhance indirect deception detection. This was studied by inducing half of one hundred and sixty-eight participants with mild psychological stress and then having them judge video material that depicted someone telling either a truth or a lie. The results showed that, although participants were able to distinguish truth from lie slightly more accurate than chance would predict when asked both directly and indirectly, stress did not significantly enhance this ability. Even though not significant, the results did show a pattern consistent with the hypothesis.

3 Improvement in Deception Detection with Stress 3 People are generally not very accurate at detecting deception (Bond & DePaulo, 2006). Yet being able to detect deception accurately may have had an evolutionary advantage (Gintis, Henrich, Bowles, Boyd, & Fehr, 2008), granting the possibility of avoiding individuals with bad intentions. This evolutionary advantage in detecting deception may have ensured that reading others intentions is something people are attuned to: When encountering an outgroup member, stress might have been induced (Acquas, Wilson, & Fibiger, 1996), and this stress, may have led to better reading of others. This could be due to its presumed effect of enhancing an intuitive way of thinking (Starcke, & Brand, 2012), which in turn may lead to enhanced accuracy of detecting deception (Albrechtsen, Meissner, & Susa, 2009). In the current study, we thus test the hypothesis that stress enhances accuracy in deception detection when measured indirectly. Even though detecting deception accurately may have been even more beneficial in the past, it can still be advantageous for people today. Despite this, several lines of research have shown that people are generally not that great at detecting deception (Bond & DePaulo, 2006), showing accuracy levels around chance level or just slightly above. Furthermore, there has been a lot of research about whether specific groups of people might be more accurate at detecting deception. A meta-analysis found no differences in accuracy were found between the sexes (Aamodt & Custer, 2006). Aamodt and Custer also found that neither experience nor education increases the accuracy of detecting deception. However, a recent meta-analysis showed that training could improve the accuracy by which deception is detected, but with small to medium effect sizes (Hauch et al., 2014). Overall, it seems that distinguishing truth from lies is hard for people, even when trained for this specific task. However, it may be that relying on intuition instead of relying on deliberate processing could improve accuracy in deception detection. A study by Albrechtsen et al. (2009) shows

4 two different ways in which intuition can improve deception detection. The first was by 4 showing people either a very short 15 second video or a longer 3 minute long video. They found that participants in the 15 second condition did better on a deception detection task, suggesting that when participants had to rely on intuition, due to limited time, they performed better. In their second experiment they made one group of participants do a concurrent task, while the other group was able to deliberate upon and consciously process the detection deception task. Again it was shown that intuition improves the accuracy in deception detection tasks. In the condition where participants had a concurrent task, participants were significantly more accurate in their judgments. In the current study we manipulate stress, which, through its effect of enhancing an intuitive way of thinking may lead to better detection as well. Other research also shows that people are better at detecting deception when intuition is induced through the use of indirect measures (DePaulo, Jordan, Irvine, & Laser, 1982, Vrij, Edward, & Bull, 2001). Using indirect measures could mean the participant answers questions like: Do you like the person who says this?. These types of indirect questions may arguably be answered relying on lower level processing. Asking people how they feel about someone instead of directly asking whether the person is lying could also help them focus on nonverbal behavior more. We argue that a possible reason for intuition having positive effects on the accuracy of deception detection could be due to intuition inducing a more holistic awareness of one s surrounding, making nonverbal behaviour of the body more salient. This argument can be explained more thoroughly by combining two seemingly unrelated studies. Dovidio, Kawakami and Gaertner (2002) have shown that people form an opinion of others based more on non-verbal behaviour than their verbal behaviour (Dovidio, Kawakami, & Gaertner, 2002). Vrij, Edwards, Roberts, & Bull (2000) argue that on the basis of non-verbal behaviour alone, 78% of lies and truths could be distinguished successfully.

5 This is true even though people mostly seem to look at the face when trying to detect 5 deception and ignore the cues of the rest of the body (Ekman & Friesen, 1974). It could thus be so that relying on how you feel about a certain person, a feeling that is shaped by nonverbal behaviour of this person, may be the better way of detecting deception if intuition makes you focus on the target persons entire body. This may reinforce previous statements by Albrechtsen et al. (2009), proposing that people could be better at distinguishing truth-tellers from liars when they rely on their intuition. We suggest that measuring deception detection in an indirect manner could enhance reliance on intuition. To further enhance this reliance, and to make people view their surroundings more holistically instead of narrowly focussed, we manipulate stress. From the above we argue that stress enhances lower level processing, and that these processes are exactly what could enhance deception detection. We test whether a state of anticipatory stress could enhance the ability to detect deception, through stress inducing a lower processing style. Intuition may have been beneficial to detect whether the intentions of this stranger were good or bad and so helped to avoid strangers with bad intentions. The induced stress and resulting intuitive way of thinking could thus have had an evolutionary advantage in detecting deception in strangers. We therefore aim to test whether people who are experiencing stress could be better at detecting deception in others. We propose this works due to a more intuitive processing style that is induced by mild psychological stress, which in turn improves accuracy in detecting deception. Stress has been found to induce a lower level processing style (Starcke & Brand, 2012). It may be the case that stress evokes a more intuitive way of thinking because stress takes away the capacity to think thoroughly. Van Marle et al. (2009) argue that the initial response to a stressor is a state of indiscriminate hyper-vigilance, allocating less cognitive capacity to specifics in the environment. This would thus cause a more holistic, intuitive way

6 of reacting to the stimuli in the surrounding instead of deeply processing everything around. 6 Moreover, Starcke and Brand (2012) argue that when under stress, people rely more on lower level processing, which, in their research, led people to be more vulnerable to framing effects. These findings suggest that being under stress might enhance performance on deception detection tasks because it makes people respond more intuitively. There are, however, many kinds of stress. For example, the stress students perceive before giving a presentation is different from the stress one experiences when holding ones hand in a bucket of ice water. These are examples that differ in the source of the stress, being psychological and physical, respectively. These different sources of stress also cause different sorts of reactions. A source of stress that is often used for research is telling the participants that they are going to present in front of others. Using this manipulation has resulted in increases in heart rate and induced sweating (Kirschbaum, Pirke, & Hellhammer, 1993). This shows that psychological sources of stress can also influence ones physical reaction. It seems, however, that whatever the source of the stress may be, the stress will induce both physical and psychological reactions. In the current study participants are induced to belief they will give a presentation at the end of the experimental hour, a way of manipulating anticipatory stress We believe that the manipulation will guide ones attention towards the upcoming presentation and hereby keep prevent deliberation about the deception detection task. In this research, we aim to provide further insights in the detection of deception. Stress, in terms of arousal, is often used in deception detection research from the deceivers standpoint. Here we will investigate whether higher stress levels in the detecting end of the interaction influence the accuracy of detection. This result may occur due to the lower level processing that is involved when under stress, which may aid formation of a correct intuition about another person. This will be tested in accordance to the following reasoning. When under stress people enter a stage of indiscriminate hyper-vigilance. This hyper-vigilance leads

7 to people thinking more intuitively, which produces more accurate deception detection. In 7 short, it could be that being under stress has helped us in the past to detect deception indirectly, and that this process is still relevant today. We test this by inducing stress in participants who then judge liars and truth-tellers with both a direct and an indirect veracity judgment. Furthermore, we hope to shine light on the impact lower level processing could have on deception detection. Method Participants One hundred and eighty-one participants were recruited at Tilburg University. Most of these participants were first year psychology students, participating in experiments for course credits. Participants were able to sign up online for the experiment and were able to choose the time most convenient to them. The initial sample consisted of 78,6% females with ages around 19 (M = 19.67, SD = 2.1). We excluded those who were familiar with the target people shown in the video material that was used in this study. This exclusion was done to prevent possible altering in judgment when one is familiar with a person. Another exclusion criterion consisted of excluding participants for whom the experimenter had made additional notes during the experiment. The most prevalent of these would be excluding participants who said they did not believe the manipulation. These observations were done unobtrusively by the experiment leader and/or the experimenters in the presentation room. Analyses are based on the remaining one hundred and sixty-eight (M = 19.61, SD = 2.1), so 13 participants have been excluded from analyses. This sample consisted of 80% females. Video material The video material consisted of 16 videos, of which 8 were randomly presented to the participants, in such a way that every participant saw the truth four times and a lie four times. Additionally, participants never saw the same target person telling a lie and a truth, as the 16

8 videos contained 8 target people telling both a lie and a truth. The video material depicted 8 someone telling either a true or an untrue story about themselves. The video material used in this experiment was obtained from prior research (van t Veer, Stel, van Beest, & Gallucci, 2014). Procedure The research was done in an isolated lab room that could hold up to 12 participants at a time. Upon entering the lab participants were asked to wait until the experiment leader was ready to help them. When ready, the experimenter would lead them to their cubicle, where a computer was already prepared for the participants. The experiment leader was not aware in which condition the participants were until the participants were finished with the experiment and only a post experiment stress measure remained. First, a consent form was presented to the participants. After this participants in the experimental condition were told to prepare a five minute presentation about their presentation skills. Participants in the control condition were asked to think about their last holiday in this time, to level out the possible time difference between the conditions. After this, both conditions were presented with 8 video clips containing a target person either the truth or a lie. Each of these video clips were paired with the indirect measure asking them: How trustworthy did you think the person in the video was? and a direct measure asking Did you think the person in the video was telling the truth?. After the participants judged 8 videos, the State-Trait Anxiety Inventory (STAI; Spielberger, Gorsuch, Lushene, Vagg, & Jacobs, 1983) was used to check the manipulation. Along with this a mood measure was taken to more thoroughly check the if participants left the experiment without decreased moods. When participants were done with the STAI, participants were asked if they knew any of the target persons in the video material and if so, they were asked for whether they knew the name of any of the targets. They were then asked

9 to report their gender, age and administration numbers so they could receive their course 9 credit. After a brief unrelated task participants in the experimental condition were told to call the experimenter, who led them to another room for the presentation. Upon arriving in the presenting room, participants were told that a brief summary of the 5 minute presentation they prepared would suffice. When the presentation was over, participants were thanked for their presentation and complimented on it. Then the last mood measure and State-Trait Anxiety Inventory (Spielberger et al., 1983) were awaiting them in their cubicle to ensure the participants were sufficiently calmed down, after completing the experiment. At the end of the experiment the demographics of the participants were gathered. Participants in the control condition went straight into the last demographic measures. Results Manipulation check An independent sample T-test indicated that participants in the control condition were significantly less stressed than participants in the experimental condition, as measured by the STAI, t(142) = 5.340, p <.001, d =.9. The independent sample T-test for the mood measure also was in line with a successful manipulation (t(163) = -3,814, p <.001, d = -.6), with participants in the control condition feeling more positive (M = 64.27, SD = 16.84) than participants in the experimental condition (M = 53.53, SD = 16.84). Main results We used a paired sample T-test to check whether participants, regardless of condition, evaluated truth-tellers to be more trustworthy than liars as an indirect measure. This T-test indicated that participants rated liars less trustworthy (M = 56.38, SD = 13.84) than truthtellers (M = 58.67, SD =13.02; t(165) = , p <.05, d = -.32)

10 Next we looked at whether the condition influenced the ability to indirectly assess 10 deception detection with a general linear model, which can be seen in Figure 1. This test indicated that although people did view truth-tellers as more trustworthy than liars (F(1) = 4,437, p =.037, η² =.026), this was not significantly moderated by stress (F(1) = 2,321, p =.13, η² =.014). Although this effect did not reach conventional standards of significance, we did find a difference that was in accordance with the hypothesis (see Figure 1). Next, a one sample T-test was conducted to analyse whether participants, regardless of condition, were able to directly detect deception better than chance level (50%). This T-test showed that although participants were able to judge deception in people significantly better than chance level, it did not differ much from 50% (t(165) = , p =.001, d = -.53). We found that 54% of the judgments were accurate, which is in line with the meta-analysis by Hauch et al. (2014) showing that although improvements in deception detection are possible, these tend to be small improvements. Whereas a meta-analysis by Aamodt and Custer (2006) did not find any factors that enhanced deception detection After this, an independent sample T-test was done to see whether participants in the stress condition were able to directly assess deception in others better than their control condition counterparts. This test showed that participants weren t significantly better at judging deception directly when induced with stress (54%) than in the control condition (55%), (t(164) = -.38, p =.704, d = -.06). Lastly, we checked whether participants stress levels had decreased at the end of the experiment for participants in the experimental condition. A paired samples T-test was conducted and found a significant difference between the STAI during the experiment (M = SD = 11.41) and the STAI after the experiment (M = SD = 9.56; t(79) = 5.123, p <.001, d = 1.15), indicating that participants left the lab without any heightened stress levels. The mood measure in the experimental condition was also in line with this (t(79) = -2.96, p <

11 11 Running head: DECEPTION DETECTION AND STRESS.01, d = -.67), with participants feeling more positive after the experiment (M = 60.29, SD = 20.67) than during the experiment (M = 53.53, SD = 19.33). Discussion In accordance with the study by Vrij et al. (2000), we found that participants were capable of distinguishing truths from lies when measured in an indirect manner: Participants perceived truth-tellers to be more trustworthy than liars. Next to this we found that people are slightly better at detecting deception than chance predicts, being accurate 54% of the time. However, this was only a small improvement from chance performance. This resonates with the finding that people are typically not that great at detecting deception (Bond, & DePaulo, 2006). We did not, however, find that stress itself significantly enhanced accuracy in deception detection, either on direct or indirect measures. Even though our stress induction proved successful, as mentioned above, stress did not significantly enhance deception detection. The results of our research show that people distinguish truth-tellers from liars slightly more accurate than chance when asked directly. This difference was rather small, being accurate in 54% of the instances in distinguishing truth-tellers from liars. Another finding was that participants did perceive truth-tellers as more trustworthy than liars. Our main hypothesis, that people distinguish truths from lies more accurately when under stress and when measured by indirect means, wasn t confirmed. Although the results were in the direction we predicted, they did not reach significance, however, this does not make us disregard our hypothesis. In addition, there were some flaws in our research that may have led to a non significant result. These flaws will be discussed in the limitations section. For now we will discuss our main intuition measure more thoroughly to better illustrate how we think intuition might play a role in deception detection. The measure we used for assessing indirect deception detection revolved around the perceived trustworthiness of the target people in our video material. Perceived trustworthiness

12 12 Running head: DECEPTION DETECTION AND STRESS is an important cue for people to help navigate the social environment (van t Wout, & Sanfey 2008). This study by van t Wout and Sanfey showed that when someone is implicitly perceived as trustworthy, participants invested larger amounts of money in them. This relates to our statement that perceived trustworthiness could lead to approaching behaviour and that the opposite leads to avoiding behaviour. Like people in the past physically avoided others who were not perceived as trustworthy, people nowadays still avoid non trustworthy others by not investing their money in them. Perceived trustworthiness has thus been used to evaluate bad or good intentions in others, just as it may provide a gut reaction to someone lying. Because of the above we argue that trustworthiness has been an important guiding tool in human behaviour both in the past and in the present, due to it trustworthiness being created more intuitively than deliberately. With our main intuition measure being trustworthiness, we will now discuss another study that revolved around perceived trustworthiness. A study by Bonnefon, Hopfensitz, and De Neys (2013) elaborated on the subject of perceived trustworthiness and whether people can actually judge trustworthiness accurately in others. They measured perceived trustworthiness by having people engage in a trust game after being exposed to the trustees photo. The results showed that people can in fact judge who is trustworthy accurately. More specific findings, however, show that people are not able to come to this correct judgment explicitly, but only implicitly. They manipulated this by having participants remember a specific pattern shown in a 3 x 3 matrix while making their judgments. This would create cognitive load on the participants, that should make them rely on intuition more. This is in line with our suggestion that implicit, intuitive judgements help in increasing accuracy in deception detection when measured with perceived trustworthiness. However, another suggestion we made seems to be contradicted by this study. A key finding in the study by Bonnefon, Hopfensitz, and De Neys (2013) with regard to our study was that when the trustworthiness judgments were based on cropped photos,

13 13 Running head: DECEPTION DETECTION AND STRESS instead of full colour and full torso photos, the judgements were more accurate. In their paper they argue that facial features are the key component to judging trustworthiness accurately. This seems to contradict our statement that looking at nonverbal behaviour helps in deception detection, specifically with perceived trustworthiness as the indirect measure. However we think that this difference might occur because no nonverbal behaviour can be judged from a photo, because the person depicted cannot actually show movement. We thus argue that this shouldn t have been a problem in our research, since we used video material in which nonverbal behaviour is present. Another interesting experiment relating their study to the current study is that they also test whether cognitive load, which could result in lower level processing, harms this ability to accurately judge trustworthiness in others. The results indicate that this is not the case, in fact it seems to enhance the judging capabilities of the participants by a small margin. This result does show resemblance to the main result in the current study. Namely that stress, which could also induce lower level processing, also seems to slightly enhance deception detection when perceived trustworthiness is the dependent variable, although not significantly so. This may be due to the fact that the trustworthiness judgment is already an automatic judgment. Limitations After the research was done we came to the conclusion that one particular person shown in the videos was recognized very frequently. Including a person with whom participants are familiar in a deception detection task could possibly have interfered with what we were interested in finding. The video material used was obtained prior to our study and thus we did not account for a specific target person who could be recognized more. Future research should aim to reduce this familiarity with the target people. This could be achieved by obtaining videos from people who are not affiliated with the university, where the experiment is done.

14 The exclusion criteria used in the research could have been defined more clearly as 14 well. Participants were excluded based on whether they had received extra notes in the logbook of our study. Not all participants, however, participated under supervision of the same experimenter. It is possible that one experimenter made more detailed notes in the logbook than another, even though specific rules were set for making notes. Although it may be difficult to arrange, it would serve future research well to try to have the same experiment leader throughout the entire experiment. If this could not be achieved than some strict rules should be adhered to when obtaining results. Also it could help if the different experiment leaders would discuss the participants they excluded together. This way, future research might benefit from no unnecessary exclusions and as this obtain better results. Conclusion Many studies, unlike the current study, focus on the deceiver when studying deception detection. Devices to detect deception like the polygraph and the galvanic skin response are based on the connection between stress and deception detection. These measures, like most research on deception detection, focus on the deceiver. However, deception detection involves two individuals rather than one, namely the deceiver and also the observer. In the current study we tried to connect stress and deception detection in the observing end of interaction. Even though no significant results were found regarding our main hypothesis, we do believe that the observer in a deception detection paradigm is worth further investigation.

15 References 15 Acquas, E., Wilson, C., & Fibiger, H. C. (1996). Conditioned and unconditioned stimuli increase frontal cortical and hippocampal acetylcholine release: effects of novelty, habituation, and fear. The Journal of Neuroscience, 16, Albrechtsen, J. S., Meissner, C. A., & Susa, K. J. (2009). Can intuition improve deception detection performance? Journal of Experimental Social Psychology, 45, Aamodt, M. G., & Custer, H. (2006). Who can best catch a liar? A meta analysis of individual differences in detecting deception. The Forensic Examiner, 15, Bond, C. F., & DePaulo, B. M. (2006). Accuracy of deception judgments. Personality and Social Psychology Bulletin, 10, Bonnefon, J. F., Hopfensitz, A., & De Neys, W. (2013). The modular nature of trustworthiness detection. Journal of Experimental Psychology, 142, DePaulo, B. M., Jordan. A., Irvine, A., & Laser, P. S. (1982). Age changes in the detection of deception. Child Development, 53, DePaulo, B. M., & Kashy, D. A. (1998). Everyday lies in close and casual relationships. Journal of Personality and Social Psychology, 74, Ekman, P., & Friesen, W. V. (1974). Detecting deception from the body or face. Journal of Personality and Social Psychology, 29, Forrest, J. A., & Feldman, R. S. (2000). Detecting deception and judge s involvement: Lower task involvement leads to better lie detection. Personality and Social Psychology Bulletin, 26, Gintis, H., Henrich, J., Bowles, S., Boyd, R., & Fehr, E. (2008) Strong reciprocity and the roots of human morality. Social Justice Research, 21, Hauch, V., Sporer, S. L., Michael, S. W., & Meissner, C. A. (2014). Does training improve the detection of deception? A meta analysis. Communication Research. doi:

16 / Kirschbaum, C., Pirke, K. M., Hellhammer, D. H. (1993). The Trier Social Stress Test a tool for investigating psychobiological stress responses in a laboratory setting Neuropsychobiology, 28, van Marle, H. J. F., Hermans, E. J., Qin, S., Fernández, G. (2009). From specificity to sensitivity: How acute stress affects amygdala processing of biologically salient stimuli. Biological Psychiatry, 66, Spielberger, C. D., Gorsuch, R. L., & Lushene, R. E. (1970). Manual for the state-trait anxiety inventory. Palo Alto, CA: Consulting Psychologists Press. Starcke, K., & Brand, M. (2012). Decision making under stress: A selective review. Neuroscience and Biobehavioral Reviews, 36, van t Veer, A. E., Stel, M., van Beest, I. & Gallucci, M. (2014). Registered report: Measuring unconcious deception detection by skin temperature. Frontiers in Psychology, 5. Vrij, A., Edward, K., & Bull, R. (2001). Police officers ability to detect deceit: The benefit of indirect deception detection measures. Legal and Criminolical Psychology, 6, Vrij, A., Edward, K., Roberts, K. P., & Bull, R. (2000). Detecting deceit via analysis of verbal and nonverbal behavior. Journal of Nonverbal Behavior. 24, van t Wout, M., Sanfey, A. G. (2008). Friend or foe: The effect of implicit trustworthiness judgements in social decision making. Cognition, 108, Zuckerman, M., DePaulo, B. M., & Rosenthal, R. (1981). Verbal and nonverbal communication of deception. Advances in Experimental Social Psychology, 14, 1-59.

17 17 Figure 1. Perceived Trustworthiness for Lies and Truths by Condition Stress Control Lies Truth Figure 1. Estimated means of perceived trustworthiness for lies and truth by participants being under stress or not (control).