Posts tagged synchronization
Articles and news from the latest research reports.
Keeping to the beat is no mean feat: Scientists reveal how two tracks of music become one
How does a DJ mix two songs to make the beat seem common to both tracks? A successful DJ makes the transition between tracks appear seamless while a bad mix is instantly noticeable and results in a ‘galloping horses’ effect that disrupts the dancing of the crowd. How accurate does beat mixing need to be to enhance, rather than disrupt perceived rhythm?
In a study published today (Wednesday 21 May 2014) in the journal Proceedings of the Royal Society B, scientists from the Universities of Birmingham and Cambridge present a new model that predicts whether or not two tracks will seem to share a common beat. This model also promises to help us understand how groups of people often start moving in synchrony, for example, football fans bouncing up and down at a stadium, or crowds falling into step when walking over a bridge.
‘We found that the time window in which two beat lines are heard as one isn’t fixed - it changes according to the statistical properties of each beat line, including how consistent or predictable they are,’ said Dr Mark Elliott, lead researcher on the study from the University of Birmingham’s School of Psychology. ‘For example, with two very consistent beat lines we only allow a very small time difference between them before we consider them to be separate. By analogy, given that DJs tend to play songs with a strong bass beat, they need to be very accurate in aligning the beats of the two songs if they are to be heard as one so as not to disrupt the flow of dancing. Our model and experiments reveal the timing properties of separate beat lines that determine whether they will be heard as one or two.’
Dr Elliott and his colleagues tested their model using a laboratory task that involved people tapping their fingers in time with two similar beat lines played simultaneously, one defined by high pitched tones, the other low pitched tones. The concurrency of the lines was varied such that the high and low pitched tones were played close together in time or far apart. Furthermore, the separation between the high-low tones was either consistent or randomly varied across the experiment. The researchers determined when people change from tapping along to a single beat formed from the two tones or targeted one of the tones while ignoring the other. They found that the time separation between tones that was required for people to judge them as distinct beats varied according to the consistency of the timings between the tones. Subsequently, these judgments influenced the timing of their movements.
Dr Elliott added, ‘People develop an expectation of when in time the next beat will occur. In defining the beat, they use the separation and consistency of the beat lines to determine whether the two tones should be combined together or whether just one tone should be attended to and the other ignored. Our model was able to predict the timing of participants’ movements based on the timing statistics of the tones we presented. Therefore, it not only allows us to calculate whether two beats will be heard as one, but also means we can predict the subtle effects the perception of an underlying rhythm can have on the movements people make to keep in synchrony with more complex beats.’
Dr Elliott is currently involved in a study, in collaboration with the University of Leeds, investigating the timing accuracy of movements in professional DJs compared to classical musicians and non-musicians. In addition, the findings of the current research are being applied to other areas: ‘We are currently investigating how spontaneous synchronisation of movements occurs within crowds. For example, in football stadiums the crowd sometimes starts to bounce up and down together. When the crowd moves together like this, it can create problems with structural vibration. Working with vibration engineers from the Universities of Sheffield and Exeter, we are applying our models to understand how such crowd dynamics might arise from the way each person adjusts their timing in relation to timing information from the people around them.’
(Source: birmingham.ac.uk)
Why don’t apes have musical talent, while humans, parrots, small birds, elephants, whales, and bats do? Matz Larsson, senior physician at the Lung Clinic at Örebro University Hospital, attempts to answer this question in the scientific publication Animal Cognition.
In his article, he asserts that the ability to mimic and imitate things like music and speech is the result of the fact that synchronised group movement quite simply makes it possible to perceive sounds from the surroundings better.
The hypothesis is that the evolution of vocal learning, that is musical traits, is influenced by the need of a species to deal with the disturbing sounds that are created in connection with locomotion. These sounds can affect our hearing only when we move.
“When several people with legs of roughly the same length move together, we tend to unconsciously move in rhythm. When our footsteps occur simultaneously, a brief interval of silence occurs. In the middle of each stride we can hear our surroundings better. It becomes easier to hear a pursuer, and perhaps easier to conduct a conversation as well,” explains Larsson.
A behaviour that has survival value tends to produce dopamine, the “reward molecule”. In dangerous terrain, this could result in the stimulation of rhythmic movements and enhanced listening to surrounding sounds in nature. If that kind of synchronized behaviour was rewarding in dangerous environments it may as well have been rewarding for the brain in relative safety, resulting in activities such as hand- clapping, foot-stamping and yelping around the campfire. From there it is just a short step to dance and rhythm. The hormone dopamine flows when we listen to music.
A new experimental method allows the spontaneous synchronization of arm motions by pairs of Japanese macaques to be observed under controlled conditions
Humans often synchronize their movements when, for example, we cooperate to move a piece of furniture. We also synchronize gestures and facial expressions when we interact. Coordinated actions are in fact surprisingly common in the animal kingdom, as exemplified by the flocking of birds and the schooling of fish. Such behaviors, however, have to date only been observed in the wild. Yasuo Nagasaka and colleagues from the Laboratory for Adaptive Intelligence at the RIKEN Brain Science Institute have now devised the first method for observing coordination under experimental conditions.
The researchers individually trained three Japanese macaque monkeys to press two buttons repeatedly and alternately with one hand. They then recorded the monkeys performing this task with a video camera and motion capture device.
Nagasaka and his colleagues later paired the monkeys and had them perform the task again while facing each other. Initially, each monkey in a pair pressed the buttons at different speeds. However, after a certain amount of time, the two monkeys spontaneously synchronized their button presses by altering the speed of their actions so that their button presses became harmonized with those of their partner.
The speed of repeated button presses differed among the three pairs of monkeys, as did the timing of the synchrony. In one pair, the button presses were synchronized but one monkey was always delayed by 1 millisecond, while in another the delay was 13 milliseconds. In all cases, however, the timing of the actions became closely matched, and the delay seemed to be dependent on exactly which monkeys had been paired together.
The researchers then played back the video recordings of the monkeys performing the task at different speeds while a monkey watched. The monkeys sped up or slowed down their button presses to harmonize their actions with those of the ‘virtual’ monkey, and they seemed to prefer to slow down their button presses, perhaps to save energy.
In a final set of experiments, the research team allowed the real monkeys to either see or hear the video recordings, and found that visual information is far more important than auditory information for synchronization.
“We believe that this spontaneous synchronization plays an important role in the building of social bonds, and we are now looking for the brain areas responsible,” says Nagasaka. “This could be fundamental to understanding the brain itself, and also the social interaction deficits in conditions such as autism.”
A video showing the spontaneous synchronization of monkey actions can be found here.
Humans have a tendency to spontaneously synchronize their movements. For example, the footsteps of two friends walking together may synchronize, although neither individual is consciously aware that it is happening. Similarly, the clapping hands of an audience will naturally fall into synch. Although this type of synchronous body movement has been observed widely, its neurological mechanism and its role in social interactions remain obscure. In a new study, led by cognitive neuroscientists at the California Institute of Technology (Caltech), researchers found that body-movement synchronization between two participants increases following a short session of cooperative training, suggesting that our ability to synchronize body movements is a measurable indicator of social interaction.
"Our findings may provide a powerful tool for identifying the neural underpinnings of both normal social interactions and impaired social interactions, such as the deficits that are often associated with autism," says Shinsuke Shimojo, Gertrude Baltimore Professor of Experimental Psychology at Caltech and senior author of the study.
Shimojo, along with former postdoctoral scholar Kyongsik Yun, and Katsumi Watanabe, an associate professor at the University of Tokyo, presented their work in a paper published December 11 in Scientific Reports, an online and open-access journal from the Nature Publishing Group.
"The most striking outcome of our study is that not only the body-body synchrony but also the brain-brain synchrony between the two participants increased after a short period of social interaction," says Yun. "This may open new vistas to study the brain-brain interface. It appears that when a cooperative relationship exists, two brains form a loose dynamic system."
The team says this information may be potentially useful for romantic or business partner selection.
"Because we can quantify implicit social bonding between two people using our experimental paradigm, we may be able to suggest a more socially compatible partnership in order to maximize matchmaking success rates, by preexamining body synchrony and its increase during a short cooperative session" explains Yun.