Ergastava transkraniaalse magnetstimulatsiooni mõju petukäitumisele

The present study investigated the effects of excitation of the dorsolateral prefrontal cortex (DLPFC) with repetitive transcranial magnetic stimulation (rTMS) on deceptive behaviour. The event-related potential (ERP) component P300 is well known as a neural marker of deception. P300 amplitude was examined in response to critical, familiar, and neutral stimuli in a task similar to the concealed information test. The electroencephalography (EEG) of 13 volunteers was recorded combined with rTMS. We did not find a difference in response to rTMS between right and left DLPFC as initially expected. However, TMS elicited a higher mean P300 amplitude to the critical stimulus compared to sham condition. Therefore, noninvasive prefrontal cortex excitation by rTMS can be used to increase the sensitivity of P300 to critical items in an analogue of the concealed information test

What's on your mind? Recent advances in memory detection using the concealed information test

Lie detectors can be applied in a wide variety of settings. But this advantage comes with a considerable cost: False positives. The applicability of the Concealed Information Test (CIT) is More limited, yet when it can be applied, the risk of false accusations can be set a priori at a very low level. The CIT assesses the recognition of; critical information that is known only by the examiners and the culprit, for example, the face a an accomplice. Large effects are Obtained with the CIT, whether combined with peripheral, brain, or Motor responses. We see three important challenges for the CIT. First, the false negative rate Of the CIT can be substantial, particularly under :realistic circumstantes. A possible solution Seems to restrict the CIT to highly Salient details. Second, there exist effective faking strategies. Future research will tell whether faking can be detected or even prevented (e.g., Using Overt measures). Third, recognition of critical crime detail's does not necessarily result from criminal activity. It is therefore important to properly embed the CIT in the investigative process, While taking care when drawing conclusions from the test outcome (recognition, not guilt)

Automatic blush detection in ‘concealed information’ test using visual stimuli

Blushing has been identified as an indicator of deception, shame, anxiety and embarrassment. Although normally associated with the skin coloration of the face, a blush response also affects skin surface temperature. In this paper, an approach to detect a blush response automatically is presented using the Argus P7225 thermal camera from e2v. The algorithm was tested on a sample population of 51 subjects, while using visual stimuli to elicit a response, and achieved recognition rates of ~77% TPR and ~60% TNR, indicating a thermal image sensor is the prospective device to pick up subtle temperature change synchronised with stimuli

Using more different and more familiar targets improves the detection of concealed information

When embedded among a number of plausible irrelevant options, the presentation of critical (e.g., crime-related or autobiographical) information is associated with a marked increase in response time (RT). This RT effect crucially depends on the inclusion of a target/non-target discrimination task with targets being a dedicated set of items that require a unique response (press YES; for all other items press NO). Targets may be essential because they share a feature - familiarity - with the critical items. Whereas irrelevant items have not been encountered before, critical items are known from the event or the facts of the investigation. Target items are usually learned before the test, and thereby made familiar to the participants. Hence, familiarity-based responding needs to be inhibited on the critical items and may therefore explain the RT increase on the critical items. This leads to the hypothesis that the more participants rely on familiarity, the more pronounced the RT increase on critical items may be. We explored two ways to increase familiarity-based responding: (1) Increasing the number of different target items, and (2) using familiar targets. In two web-based studies (n = 357 and n = 499), both the number of different targets and the use of familiar targets facilitated concealed information detection. The effect of the number of different targets was small yet consistent across both studies, the effect of target familiarity was large in both studies. Our results support the role of familiarity-based responding in the Concealed Information Test and point to ways on how to improve validity of the Concealed Information Test

Suppressing Unwanted Autobiographical Memories Reduces Their Automatic Influences: Evidence from Electrophysiology and an Implicit Autobiographical Memory Test

The present study investigated the extent to which people can suppress unwanted autobiographical memories in a mock crime memory detection context. Participants encoded sensorimotor-rich memories by enacting a lab crime (stealing a ring) and received direct suppression instructions so as to evade guilt detection in a brainwave-based concealed information test. Aftereffects of suppression on automatic memory processes were measured in an autobiographical implicit association test (aIAT). Results showed that suppression attenuated brainwave activity (P300) that is associated with crime-relevant memory retrieval, rendering innocent and guilty/suppression participants indistinguishable. However, guilty/suppression and innocent participants could nevertheless be discriminated via the late posterior negative slow wave, which may reflect the need to monitor response conflict arising between voluntary suppression and automatic recognition processes. Lastly, extending recent findings that suppression can impair implicit memory processes; we provide novel evidence that suppression reduces automatic cognitive biases that are otherwise associated with actual autobiographical memories

Orienting versus inhibition in the concealed information test: different cognitive processes drive different physiological measures

The Concealed Information Test (CIT) provides a valid tool for psychophysiological detection of concealed knowledge. However, its precise theoretical underpinnings remain a matter of debate. The differential physiological responses elicited by concealed, relevant items, relative to control items, were traditionally explained as reflecting an orienting response (OR). According to an alternative account, these responses reflect attempts to inhibit arousal. The present study examined whether and to what extent CIT detection efficiency is affected by instructions aimed at manipulating arousal inhibition (AI). One hundred and forty-eight undergraduate students completed a CIT, while electrodermal, cardiac, and respiratory measures were recorded. Half of the participants were requested to imagine that they are suspected of committing a crime and were motivated to avoid detection (presumably eliciting both OR and AI), while the other half were requested to imagine that they are witnesses of a crime and were motivated to be detected (presumably eliciting OR only). All participants were further requested to remain silent throughout the test. In both conditions, concealed items led to a similar increase in skin conductance as compared to the control items. However, the typically observed heart rate deceleration and respiratory suppression were found in suspects, but not in witnesses. These data imply that different mechanisms drive the responding of different psychophysiological measures used in the CIT, with skin conductance reflecting OR, and heart rate and respiration primarily reflecting AI

Increased motor cortex excitability for concealed visual information

Deceptive behaviour involves complex neural processes involving the primary motor cortex. The dynamics of this motor cortex excitability prior to lying are still not well understood. We sought to examine whether corticospinal excitability can be used to suggest the presence of deliberately concealed information in a modified version of the Guilty Knowledge Test (GKT). Participants pressed keys to either truthfully or deceitfully indicate their familiarity with a series of faces. Motor-evoked-potentials (MEPs) were recorded during response preparation to measure muscle-specific neural excitability. We hypothesised that MEPs would increase during the deceptive condition not only in the lie-telling finger but also in the suppressed truth-telling finger. We report a group-level increase in overall corticospinal excitability 300 ms following stimulus onset during the deceptive condition, without specific activation of the neural representation of the truth-telling finger. We discuss cognitive processes, particularly response conflict and/or automated responses to familiar stimuli, which may drive the observed non-specific increase of motor excitability in deception

Does Anonymity Matter in Electronic Limit Order Markets?

Lecture on the first SFB/TR 15 meeting, Gummersbach, July, 18 - 20, 2004We develop a model of limit order trading in which some traders have better information on future price volatility. As limit orders have option-like features, this information is valuable for limit order traders. We solve for informed and uninformed limit order traders’ bidding strategies in equilibrium when limit order traders’ IDs are concealed and when they are visible. In either design, a large (resp. small) spread signals that informed limit order traders expect volatility to be high (resp. low). However the quality of this signal and market liquidity are different in each market design. We test these predictions using a natural experiment. As of April 23, 2001, the limit order book for stocks listed on Euronext Paris became anonymous. For our sample stocks, we find that following this change, the average quoted and effective spreads declined significantly. Consistent with our model, we also find that the size of the spread is a predictor of future price volatility and that the strength of the association between the spread and volatility is weaker after the switch to anonymity.Market Microstructure; Limit Order Trading; Anonymity; Transparency; Liquidity; Volatility Forecasts

A Cutoff Procedure and Counterterms for Differential Renormalization

Explicit divergences and counterterms do not appear in the differential renormalization method, but they are concealed in the neglected surface terms in the formal partial integration procedure used. A systematic real space cutoff procedure for massless $\phi^4$ theory is therefore studied in order to test the method and its compatibility with unitarity. Through 3-loop order, it is found that cutoff bare amplitudes are equal to the renormalized amplitudes previously obtained using the formal procedure plus singular terms which can be consistently cancelled by adding conventional counterterms to the Lagrangian. Renormalization group functions $\beta (g)$ and $\gamma (g)$ obtained in the cutoff theory also agree with previous results.Comment: 28 pages, CTP#2099-DTP/92/40-UBECMPF/92/13, 2 figures (not included). (Tex problems solved and information about number of pages and figures added