Scientists have come up with a theory for why time flies when you are having fun-- and drags when you are bored.

    Scans have shown that patterns of activity in the brain change depending on how we focus on a task.

    Concentrating on time passing, as we do when bored, will trigger brain activity which will make it seem as though the clock is ticking more slowly.

    The research, by the French Laboratory of Neurobiology and Cognition, is published in the magazine Science.

    In the study, 12 volunteers watched an image while researchers monitored their brain activity using MRI scans.

    Volunteers were given a variety of tasks. In one they were told to concentrate simply on the duration of an image, in another they were asked to focus on the colour, and in a third they were asked to concentrate on both duration and colour.

    The results showed that a network of brain regions was activated when more subjects were paid attention to duration.

    It is thought that if the brain is busy focusing on many aspects of a task, then it has to spread its resources thinly, and pays less heed to time passing.

    Therefore, time passes without us really noticing it, and seems to go quickly.

    However, if the brain is not stimulated in this way, it concentrates its full energies on monitoring the passing of time.

    This may make time seem to drag, but in fact it is probably a more accurate perception of reality.

    Indeed, the researchers found that the more volunteers concentrated on the duration of the images, the more accurate were their estimates of its duration.

    Lead researcher Dr Jennifer Coull said many of the areas of the brain involved in estimating time were the same that played a key role in controlling movement, and preparing for action.

    She said this overlap suggests that the brain may make sense of time as intervals between movements, in much the same way as a musician marks time with his foot, or an athlete anticipates the sound of a starter's pistol.

    科学家们提出理论依据，解释为什么当你玩得开心的时候，时间总是过得飞快，而当你无聊的时侯，时间却过得特别慢。

    通过扫描发现，大脑活动的方式随着我们对事情的关注程度发生变化。

    我们在无聊的时候，往往把注意力集中在时间的流逝上，这样会使大脑活动产生错觉，总觉得时钟似乎走得更慢。

    法国神经生物和认知学实验室进行的此项研究发表在《科学》杂志上。

    在研究中，当12名志愿者同时看一幅图像时，研究者们用核磁共振成像扫描仪来监控他们大脑的活动。

    志愿者们被分配了各种不同的任务。一次他们被要求专注于图象持续的时间，另一次集中观察图象的色彩，第三次同时关注图象持续的时间和色彩。

    结果表明，在观看图像的过程中，注意的对象多的话，就会激活大脑区域网络。

    科学家们认为如果大脑忙于关注一项任务中的多个方面，那么它不得不分散注意力，这样就不太会注意到时间的流逝。

    所以，我们还没真正注意到时间，时间就已经过去了，而且似乎过得特别快。

    然而，如果大脑并没有受到这样的刺激，它就会把全部精力用来监控时间的流逝。

    这样就会觉得时间过得特别慢，但是事实上这可能是对现实情况的更准确的认识。

    事实上，研究者们发现，志愿者们越是注意图像持续的时间，他们对于时间的估计就越准确。

    主任研究员詹尼弗·库尔博士说，大脑中有许多参与估计时间的区域，同时他们对行为控制和行动准备也起到重要的作用。

    她说这种区域重合说明大脑在活动的间隙可能会注意到时间，在很大程度上就像音乐家用脚来记录时间、运动员预料发令员的枪声一样。