Dimensioning Links for IP Telephony

Transmitting telephone calls over the Internet causes problems not present in current telephone technology such as packet loss and delay due to queueing in routers. In this undergraduate thesis we study how a Markov modulated Poisson process is applied as an arrival process to a multiplexer and we study the performance in terms of loss probability. The input consists of the superposition of independent voice sources. The predictions of the model is compared with results obtained with simulations of the multiplexer made with a network simulator. The buffer occupancy distribution is also studied and we see how this distribution changes as the load increases

Alcohol and remembering a hypothetical sexual assault: Can people who were under the influence of alcohol during the event provide accurate testimony?

We examined the influence of alcohol on remembering an interactive hypothetical sexual assault scenario in the laboratory using a balanced placebo design. Female participants completed a memory test 24 hours and 4 months later. Participants reported less information (i.e., responded ‘don’t know’ more often to questions) if they were under the influence of alcohol during scenario encoding. The accuracy of the information intoxicated participants reported did not differ compared to sober participants, however, suggesting intoxicated participants were effectively monitoring the accuracy of their memory at test. Additionally, peripheral details were remembered less accurately than central details, regardless of intoxication level; and memory accuracy for peripheral details decreased by a larger amount compared to central details across the retention interval. Finally, participants were more accurate if they were told they were drinking alcohol rather than a placebo. We discuss theoretical implications for alcohol myopia and memory regulation, together with applied implications for interviewing intoxicated witnesses

Alcohol-induced retrograde facilitation renders witnesses of crime less suggestible to misinformation

RATIONALE: Research has shown that alcohol can have both detrimental and facilitating effects on memory: intoxication can lead to poor memory for information encoded after alcohol consumption (anterograde amnesia) and may improve memory for information encoded before consumption (retrograde facilitation). This study examined whether alcohol consumed after witnessing a crime can render individuals less vulnerable to misleading post-event information (misinformation). METHOD: Participants watched a simulated crime video. Thereafter, one third of participants expected and received alcohol (alcohol group), one third did not expect but received alcohol (reverse placebo), and one third did not expect nor receive alcohol (control). After alcohol consumption, participants were exposed to misinformation embedded in a written narrative about the crime. The following day, participants completed a cued-recall questionnaire about the event. RESULTS: Control participants were more likely to report misinformation compared to the alcohol and reverse placebo group. CONCLUSION: The findings suggest that we may oversimplify the effect alcohol has on suggestibility and that sometimes alcohol can have beneficial effects on eyewitness memory by protecting against misleading post-event information

Do intoxicated witnesses produce poor facial composite images?

The effect of alcohol intoxication on witness memory and performance has been the subject of research for some time, however, whether intoxication affects facial composite construction has not been investigated. Intoxication was predicted to adversely affect facial composite construction. Thirty-two participants were allocated to one of four beverage conditions consisting of factorial combinations of alcohol or placebo at face encoding, and later construction. Participants viewed a video of a target person and constructed a composite of this target the following day. The resulting images were presented as a full face composite, or a part face consisting of either internal or external facial features to a second sample of participants who provided likeness ratings as a measure of facial composite quality. Intoxication at face encoding had a detrimental impact on the quality of facial composites produced the following day, suggesting that alcohol impaired the encoding of the target faces. The common finding that external compared to internal features are more accurately represented was demonstrated, even following alcohol at encoding. This finding was moderated by alcohol and target face gender such that alcohol at face encoding resulted in reduced likeness of external features for male composite faces only. Moderate alcohol intoxication impairs the quality of facial composites, adding to existing literature demonstrating little effect of alcohol on line-up studies. The impact of intoxication on face perception mechanisms, and the apparent narrowing of processing to external face areas such as hair, is discussed in the context of alcohol myopia theory

Editorial: The impact of alcohol and drugs on suspects', victims' and witnesses' cognition and memory

In many societies around the world, alcohol and other drug use and abuse pose major health and safety problems. There is a clear link between alcohol consumption and lack of impulse control and an increased risk of violence, which leads to a high prevalence of intoxicated victims, witnesses, and suspects—especially in relation to violent crimes. Although recent years have seen an increase in applied research on the acute effects of alcohol and other drugs on memory and cognition, especially on the topic of eyewitness memory, there are still many gaps in our knowledge. Indeed, more research is needed to further disentangle the often-complex effects of alcohol and other drugs, especially in applied forensic contexts, such as witness and suspect investigative interviewing

The effects of alcohol intoxication on accuracy and the confidence-accuracy relationship in photographic simultaneous lineups

(Summary) Acute alcohol intoxication during encoding can impair subsequent identification accuracy, but results across studies have been inconsistent, with studies often finding no effect. Little is also known about how alcohol intoxication affects the identification confidence-accuracy relationship. We randomly assigned women (N = 153) to consume alcohol (dosed to achieve a 0.08% blood alcohol content) or tonic water, controlling for alcohol expectancy. Women then participated in an interactive hypothetical sexual assault scenario and, 24 hours or 7 days later, attempted to identify the assailant from a perpetrator present or a perpetrator absent simultaneous line-up and reported their decision confidence. Overall, levels of identification accuracy were similar across the alcohol and tonic water groups. However, women who had consumed tonic water as opposed to alcohol identified the assailant with higher confidence on average. Further, calibration analyses suggested that confidence is predictive of accuracy regardless of alcohol consumption. The theoretical and applied implications of our results are discussed

Intoxicated witnesses: Testing the validity of the Alcohol Myopia Theory.

In an assessment of the Alcohol Myopia Theory, the effects of alcohol on an eyewitness’s recall of high and low salience details were investigated. In laboratory study 1, participants watched a staged videoed theft whilst either sober (control or placebo), above (MBAC=0.09%) or below (MBAC=0.06%) the UK drink-drive limit. A week later a free-recall and recognition test were completed. Intoxication was not found to reduce recall accuracy using either recall task. In Study 2, while on a night out participants watched the videoed theft with high (MBAC=0.14%) or low (MBAC=0.05%) BAC’s. A week later the free-recall and recognition test were attempted. High BAC’s were seen to impair recall when memory was assessed through free-recall but not with the recognition test. Neither study found the attention narrowing predicted by AMT using either recall technique, although poor recall for low salience details in all groups may have contributed to this result

Alcohol-intoxicated eyewitnesses´ memory

Eyewitnesses are an important source of information in many criminal investigations. However, the memory of an eyewitness is not always accurate, and errors may occur that have serious consequences. Alcohol-related crimes are common and therefore, intoxicated witnesses are common. However, only a handful of published studies have described how alcohol affects eyewitnesses’ memory. The overall aim of the research described in this thesis was to examine how alcohol affects eyewitnesses’ memory. The thesis comprises three studies, which followed similar general procedures. The participants in the studies consumed an alcoholic or non-alcoholic beverage during a 15-minute period and then witnessed a film that depicting a staged kidnapping. The retention interval and recall format varied between the studies. The aim of Study I was to examine the influence of alcohol on eyewitnesses’ performances in a line-up setting. The participants (N = 123) were randomly assigned to a 3 (Beverage: control [0.0 g/kg] versus lower alcohol dosage [0.4 g/kg] group versus higher alcohol dosage [0.7 g/kg] group) × 2 (Line-up: target-present versus target-absent) between-subject design. One week after alcohol intoxication and the critical event, the participants were exposed to the line-up. The results showed no significant difference between the groups in terms of performance in the line-up, under either the target-present or the target-absent condition. In general, the participants performed better than chance at identifying the culprit. However, all witnesses performed quite poorly. Study II (N = 126) examined the effects of alcohol (Beverage: control [0.0 g/kg] versus lower alcohol dosage [0.4 g/kg] group versus higher alcohol dosage [0.7 g/kg] group) on the amount of information reported (completeness) and accuracy rate. There was no difference in the completeness between the control group and the higher alcohol dosage group or between the control group and the lower alcohol dosage group. When comparing the two alcohol groups, participants in the higher alcohol dosage group remembered fewer details than those in the lower alcohol dosage group. No differences were found between the beverage groups in recall accuracy. The aim of Study III (N = 99) was to elucidate the best time to interview intoxicated witnesses. Participants were randomly assigned to a 2 (Beverage: control [0.0 g/kg] versus alcohol dosage [0.7 g/kg] group) × 2 (Recall: repeatedly, i.e., immediate plus delayed interviews versus single, i.e., delayed interview only) mixed design. Overall, alcohol-intoxicated eyewitnesses produced less accurate testimonies than the sober witnesses. Although the difference was significant, the intoxicated witnesses were only slightly less accurate in their recollections. Both the sober and the intoxicated witnesses recalled details with a relatively high accuracy. There was no difference with regards to the amount of information reported between the intoxicated and the sober witnesses. An immediate interview was more beneficial than a delayed interview. However, the best recall was by witnesses who were interviewed twice, and this was true for both the sober and the intoxicated witnesses. New details provided at the second interview, by either group, were often correct. In summary, this thesis shows that alcohol consumption does not have a negative effect on either witness’s line-up performance (recognition) or on the amount of information reported during investigative interviews (recall). However, the accuracy of their recall was slightly impaired by consumption of alcohol (Study III). This thesis shows that representatives of the legal system may expect that witnesses with low to moderate intoxication (blood alcohol concentration <0.10%) will perform at approximately the same level as sober witnesses. It is however reasonable to assume that more profound memory impairments can be expected for witnesses with higher intoxication levels