A sensorimotor area (NIf) is required for the production of learned vocalizations

Sensory feedback is essential for the acquisition of complex motor behaviors, including birdsong. In zebra finches, auditory feedback is relayed to the descending motor pathway primarily through the nucleus interfacialis nidopalii (NIf). NIf projects to HVC - a premotor region essential for song, which projects to RA, a motor cortex analogue brain area that drives muscle activity required for vocalizations. NIf is also essential for ‘sleep replay’, a recapitulation of song-related neural dynamics in the motor pathway during sleep. Despite being one of the major inputs to the song control pathway, there is no known role for NIf in the production of zebra finch song. To address this, we reversibly inactivated NIf using TTX or Muscimol in 13 birds. We compared songs before and during inactivation and found large effects of NIf inactivation on song structure. Vocalizations after NIf inactivation resembled subsong, highly variable utterances typical of the very early phases of song learning. Subsong is driven by LMAN, the output nucleus of an avian basal ganglia circuit that projects to RA. To verify that NIf inactivations indeed switched song control from HVC to LMAN, we inactivated LMAN in conjunction with NIf in four birds. As with LMAN inactivations after HVC lesions, this manipulation led to a complete cessation of singing. We also lesioned NIf using ibotenic acid and saw the song recover within a day, consistent with previous studies. Our results show that NIf input to HVC is acutely necessary for generating learned vocal behavior in songbirds, and that in its absence vocal production reverts to subsong driven by LMAN. Absent NIf input, the song circuit reorganizes and recovers its ability to produce pre-lesion song over the course of 1-2 days, suggesting a redundant role for NIf that can be assumed by other parts of the song circuit

Nonlinear Instability of Hypersonic Flow past a Wedge

The nonlinear stability of a compressible flow past a wedge is investigated in the hypersonic limit. The analysis follows the ideas of a weakly nonlinear approach. Interest is focussed on Tollmien-Schlichting waves governed by a triple deck structure and it is found that the attached shock can profoundly affect the stability characteristics of the flow. In particular, it is shown that nonlinearity tends to have a stabilizing influence. The nonlinear evolution of the Tollmien-Schlichting mode is described in a number of asymptotic limits

Getting into the minds of pairs of liars and truth tellers: An examination of their strategies

Abstract: We examined the strategies used by 20 pairs of liars and 20 pairs of truth tellers when they were given the opportunity to prepare themselves for an interview in which they would be questioned about their whereabouts during a given period of time. More lying than truth telling pairs prepared themselves for the interviews. The truth tellers and liars who did prepare themselves used different verbal strategies but the same nonverbal strategies. Regarding verbal strategies, truth tellers were predominantly concerned with telling everything they could remember. In contrast, liars thought of answers they could give to possible questions but also decided to be vague so that they would not contradict each other. Regarding nonverbal strategies, both truth tellers and liars tried to suppress nervous behaviours. These findings explain why truth tellers are typically more detailed than liars but also why liars are typically equally consistent as truth tellers, at least when answering questions they have anticipated. Implications for interview techniques to detect deceit are discussed. Keywords: liars' and truth tellers verbal ane nonverbal strategies, lie detection. In their attempts to detect lies it will benefit criminal investigators to obtain insight into how truth tellers and liars prepare themselves for their interviews . This insight could predict what truth tellers and liars say and how they behave during an interview, and criminal investigators could use this insight to develop effective theory-based lie detection protocols. Given the importance, it is surprising that truth tellers' and liars' strategies to appear credible in an interview have been understudied for a long time The present strategies study differed from the previous studies in two important ways. First, previous studies concentrated on the strategies developed by individual truth tellers and liars whereas we focused on pairs of truth tellers and pairs of liars. We believe that this reflects an important aspect of real life, because criminals often work in groups or networks rather than alone. Second, after being interviewed, we asked the truth tellers and liars whether there were awkward moments during the interview that could have jeopardised their credibility. In theory, truth tellers and liars face the same task during the interview: They both need to convince an interviewer that they are innocent Those pairs of truth tellers and liars who do develop a joint strategy to appear credible are likely to develop different verbal strategies to achieve this aim. Truth tellers can simply disclose in detail during the interview everything that happened. In contrast, liars cannot do this but have to fabricate a story. They need to make sure that the information they give sounds plausible, but does not contradict facts that the interviewer knows or may find out. In case two liars are interviewed about the same event, as happened in the present experiment, they should also make sure they provide the same information and do not contradict each other. Therefore, truth tellers are likely to report that they discussed as a pair that they would say in the interview what had happened, and that they ran through the event together to remind each other of the details of the event (Hypothesis 2). In contrast, liars are likely to report that they, as a pair, had agreed on which fabricated story to tell during the interview to make sure that their stories would match one another. Liars further may have agreed not to disclose too much detail, because the more detail they provided, the higher the chance that they would contradict one another or say something the interviewer knows to be untrue (Hypothesis 3). The pairs of truth tellers and liars who develop a joint strategy to appear credible will develop similar nonverbal strategies to achieve this aim. People overwhelmingly believe that displaying nervous behaviour appears suspicious, in particular gaze aversion, fidgeting or other sorts of movements After the interview we asked truth tellers and liars whether they had experienced awkward moments during the interview. Liars' tendency to take their credibility less for granted than truth tellers will make them more conscious of themselves during the interview and probably more aware of imperfections during such interviews. In addition, because lying is often cognitively more demanding than truth telling If asked what they have said wrong, truth tellers and liars are likely to provide different answers. People typically believe that providing accounts that lack detail, mentioning that they cannot remember something, or contradicting each other, will sound suspicious If asked what they have done wrong, truth tellers and liars are both likely to report the same thing: They will probably believe that they have shown nervous behaviours such as gaze aversion, fidgeting and other type of movements (Hypothesis 9). METHOD Participants Eighty undergraduate students, 13 males and 67 females, participated. Their average age was M = 19.36 (SD = 2.29) years. Procedure The event was modified from Truth Tellers On arrival at the Psychology Department laboratory, each pair of truth tellers (20 pairs, 40 truth tellers in total) was told that the study would take place at Gunwharf, a shopping centre near the Psychology Department. An experimenter (Sharon) brought the pair to Gunwharf. On the way Sharon pretended to receive a text message saying that the experiment is running late. She therefore brought the pair of participants to one of three restaurants and told them that they can spend up to £15 on lunch (but no alcohol). Three research-assistant observers were already in the three designated restaurants to check that all pairs would have lunch and stay in the restaurant (all pairs did). After 45 minutes Sharon returned to the restaurant. The truth tellers were told that, as the study was running late, the format had changed slightly and that the study would be carried out in the Psychology Department. When the participants returned to the Psychology Department laboratory, a second experimenter (Jackie) told each pair of truth tellers that they were both suspected of having committed a crime (taking two £5 notes out of a room) when they had lunch together and that in about 10 minutes they would be interviewed individually about their alibi. They were told that their task is to convince the interviewer that their alibi is true, having lunch together in Gunwharf. The interviewer did not know if the alibi was true but made a judgement at the end of the interview. To motivate the participants to perform well during the interview they were informed that if the interviewer believed the participant, they would be paid £10; in contrast, if she did not believe the participant, they would not receive any money, and may be asked to write a statement about their whereabouts during lunch-time instead. The pairs were then left alone together for 10 minutes. After 10 minutes each pair was taken to two different cubicles to fill out individually the pre-interview questionnaire. The questionnaire asked about the participant's gender and age, and whether he or she had discussed an interview strategy together with the other participant (yes/no). If they did not develop a strategy we asked them via an open-ended question why they did not do this. In case they did develop a strategy, we asked them via an open-ended question to describe it. After completing the questionnaire each participant was taken individually into the interview room where they were interviewed. Questions were asked about the layout of the restaurant, the food they had consumed, and the conversations they had. After the interview the participants individually completed the post-interview questionnaire, which asked (i) how motivated they were to perform well during the interview (7-point Likert scale ranging from [1] very unmotivated to [7] very motivated); (ii) to estimate the likelihood of receiving £10 and having to write a statement (both on 7-point Likert scales ranging from [1] very unlikely to [7] very likely); and (iii) whether they had experienced any awkward moments during the interview (answers were given on a 7-point Likert scales ranging from [1] not at all to [7] plenty). This question was followed by two specific questions about whether there was something (1) they had said or (2) done during the interview that raised suspicion (answers were given on 7-point Likert scales ranging from [1] not at all to [7] definitely). Via two open-ended questions we asked the participants to list (1) the speech content and (2) nonverbal behaviours that they thought had raised suspicion. 1 The answers to the open-ended questions are not statistically tested for two reasons. These qualitative answers are not really suitable for quantitative statistical testing. Moreover, for some questions too few participants provided answers to enable statistical testing. Liars At arrival in the Psychology Department laboratory, the second experimenter (Jackie) told each pair of liars (20 pairs, 40 liars in total) that two £5 notes were hidden in a purse in an empty room. Each pair was instructed to go together to the room, take the money out of the purse, share it and return. When they returned from taking the money, the pairs in the were told that they were suspected of having taken money out of a purse, that they would be interviewed individually in 10 minutes about this and that they had 10 minutes to fabricate an alibi about their whereabouts during the last 45 minutes. This alibi is that someone called Sharon took them as a pair to Gunwharf for an experiment, that the experiment was running late, and that they were therefore taken to a restaurant to have lunch together, paid for by the Department, and that Sharon returned after 45 minutes. They were then told that their task in the interview would be to convince the interviewer that they actually were in the restaurant as a pair. The interviewer would not know if the alibi is true but would make a judgement at the end of the interview. If the interviewer believes them, they would be paid £10, and could keep the money they took out of the wallet, but if she does not believe them, they would not receive the additional £10, and may be asked to write a statement about their whereabouts instead. The pairs were then left alone together for 10 minutes. After 10 minutes the pair of suspects were taken to two different cubicles to fill out the pre-interview questionnaire individually (see above). After completing the questionnaire each was taken separately into the interview room and were interviewed. After the interview the participants completed the post-interview questionnaire individually (see above). The participants were then debriefed, thanked and given £10 apiece. 2 1 Participants did not know whether or not the interviewer had believed them when they completed the post-interview questionnaire. 2 The condition reported in the text is the 'immediate' condition. In another condition, the participants (truth tellers and liars) were sent home after their lunch/stealing the money and asked to return one week later. This delay factor is not relevant for this article and no hypotheses about it were formulated. However, to precise the error term we included the Delay factor as factor in our statistical analyses. RESULTS Motivation and Manipulation Check

On the instability of Goertler vortices to nonlinear travelling waves

Recent theoretical work by Hall and Seddougui (1989) has shown that strongly nonlinear, high wavenumber Goertler vortices developing within a boundary layer flow are susceptible to a secondary instability which takes the form of travelling waves confined to a thin region centered at the outer edge of the vortex. The case is considered in which the secondary mode could be satisfactorily described by a linear stability theory and herein the objective is to extend this investigation of Hall and Seddougui (1989) into the nonlinear regime. It was found that at this stage not only does the secondary mode become nonlinear but it also interacts with itself so as to modify the governing equations for the primary Goertler vortex. In this case then, the vortex and the travelling wave drive each other and, indeed, the whole flow structure is described by an infinite set of coupled, nonlinear differential equations. A Stuart-Watson type of weakly nonlinear analysis of these equations is undertaken and concluded, in particular, that on this basis there exist stable flow configurations in which the travelling mode is of finite amplitude. Implications of the findings for practical situations are discussed and it is shown that the theoretical conclusions drawn here are in good qualitative agreement with available experimental observations

The effects of suction on the nonlinear stability of the three-dimensional boundary layer above a rotating disc

There exist two types of stationary instability of the flow over a rotating disc corresponding to the upper branch, inviscid mode and the lower branch mode, which has a triple deck structure, of the neutral stability curve. A theoretical study of the linear problem and an account of the weakly nonlinear properties of the lower branch modes have been undertaken by Hall and MacKerrell respectively. Motivated by recent reports of experimental sightings of the lower branch mode and an examination of the role of suction on the linear stability properties of the flow here, the effects are studied of suction on the nonlinear disturbance described by MacKerrell. The additional analysis required in order to incorporate suction is relatively straightforward and enables the derivation of an amplitude equation which describes the evolution of the mode. For each value of the suction, a threshold value of the disturbance amplitude is obtained; modes of size greater than this threshold grow without limit as they develop away from the point of neutral stability

Media Coverage of EPA\u27s Draft Dioxin Reassessment Report

Using content analysis, the authors examine the utility of news media in democratic decision making

On the receptivity problem for Goertler vortices: Vortex motions induced by wall roughness

The receptivity problem for Goertler vortices induced by wall roughness is investigated. The roughness is modelled by small amplitude perturbations to the curved wall over which the flow takes place. The amplitude of these perturbations is taken to be sufficiently small for the induced Goertler vortices to be described by linear theory. The roughness is assumed to vary in the spanwise direction on the boundary layer lengthscale, while in the flow direction the corresponding variation is on the lengthscale over which the wall curvature varies. In fact the latter condition can be relaxed to allow for a faster streamwise roughness variation so long as the variation does not become as fast as that in the spanwise direction. The function which describes the roughness is assumed to be such that its spanwise and streamwise dependences can be separated; this enables progress by taking Fourier or Laplace transforms where appropriate. The cases of isolated and distributed roughness elements are investigated and the coupling coefficient which relates the amplitude of the forcing and the induced vortex amplitude is found asymptotically in the small wavelength limit. It is shown that this coefficient is exponentially small in the latter limit so that it is unlikely that this mode can be stimulated directly by wall roughness. The situation at 0(1) wavelengths is quite different and this is investigated numerically for different forcing functions. It is found that an isolated roughness element induces a vortex field which grows within a wedge at a finite distance downstream of the element. However, immediately downstream of the obstacle the disturbed flow produced by the element decays in amplitude. The receptivity problem at larger Goertler numbers appropriate to relatively large wall curvature is discussed in detail