A  Traditionally, Australian Aboriginal people used to live in family groups, a few of which would join together to form larger groups known to sociologists as bands or hordes. To take part in important ceremonies or gatherings such as initiations, these bands came together as a single tribe, making a group of a hundred to several hundred people. In turn, these tribes sometimes met in still larger groups of a thousand or more. Aboriginal society was organised in three different ways: according to geographical structuring, religious/totemic structuring, and kinship structuring.

B  Firstly, there was the geographical structuring of society, in which tribes of perhaps 500 people were made up of a number of bands of up to 20 people, each of which occupied a specific area. These bands were economic groups which would join together for day-to-day hunting and other food gathering. However, the term 'band' is given to this type of group by non-Aboriginal observers, and is not a distinct group in the minds of Aboriginal people, who regard themselves rather as belonging to a particular tribe or totemic group.

C  In Aboriginal Australia, tribes are groups made up of people sharing the same language, customs and general laws. The people of a tribe share a common bond and, in their own language, the word for 'man' is often the word used for the name of the tribe. Some tribal groups now also use the English term 'nation' to describe themselves, as, for example, the Larrakeyah tribe around Darwin in Australia's Northern Territory who call themselves the 'Larrakeyah nation'. Tribes were generally not groups concerned with making war, and were not led by a chief. When Europeans first settled in Australia at the end of the 18th century there were an estimated 500 Aboriginal tribes. Of these, around 400 still have people representing them in the centre and north of Australia, where the tribal structure is still largely intact.

D  The second way in which Aboriginal society was organised is religious and totemic. On a religious level, Aboriginal society in Australia was divided into two 'moieties' (a term used by European anthropologists) or halves. Within each moiety are significant animals, plants or places connected to the time of creation, which Aboriginal people call the 'Dreamtime'. For example, in the northern Kimberley area of Western Australia, the two moieties are represented by the two birds, Wodoi, the spotted nightjar, and Djungun, the owlet nightjar, who are said to have fought in the Dreamtime. Wodoi is associated with certain plants such as the edible cabbage palm, while Djungun is connected to a fish called the rock cod and a bird, the corella.

E  Each person, as well as belonging to one or the other moiety, also belongs to a totemic group. A totem is an animal, plant or other object which is believed to be ancestrally related to a person. In the Kimberley example given above, people belonging to the Wodoi moiety call the spotted nightjar their father, but they also have other animal and plant associates. For example, Jack Kararlada, a Kimberley elder, is named after his totem, the butcher bird, or karadada in the local language. A totem can be represented by a large rock, a tree, hill, river or other land form, and may also have a man-made emblem such as a wooden pole or other decorated object. Much of Aboriginal art is connected with the imagery of totems. A person is born into one or the other moiety, with their own totems, and that does not change throughout their life. A person belonging to one moiety must marry a person of the opposite moiety, a custom which has the effect of increasing genetic variation in the group.

F  The third way that the society is structured is through the kinship system, which regulates relations between people. The kinship system is complex, needing up to 70 relationship terms to describe it. It structures obligations and behaviour among families and between members of society in general, and defines such matters as who will look after children if a parent dies, who can marry whom, who is responsible for another person's misdeeds, and who will care for the sick and the elderly. Under kinship laws, Aboriginal people may have similar family obligations to their aunts and uncles as they would to their mother or father.

G  A family group can be quite large, consisting of a man and his wives, the children from each wife, and sometimes his parents or in-laws. A man used to have from one to ten wives, but nowadays most men have just one. Interestingly, Aboriginal custom all over Australia bans a person from speaking directly to their mother-in-law. So, in traditional society, if you wanted your mother-in-law to do something for you, you would have to ask another person to ask her. When food was divided and shared around the camp fire, a mother-in-law would have her own small fire, and her son or daughter would take her some of the meat and stay to chat, or a grandchild would sit with her and act as a messenger.

Scientific research has identified a bottleneck in our brains that could suggest we are fundamentally incapable of true multitasking. If experimental findings reflect real-world performance, people who think they are multitasking are probably just underperforming in all of their parallel pursuits.

The problem, according to René Marois, a psychologist at Vanderbilt University in Tennessee, is that there's a sticking point in the brain. In order to locate this, Marois asked volunteers to watch a screen and press a key with a specific finger when a particular image appeared. Then, in a separate activity, they learned to listen to different recordings and to respond by making a specific sound. In both tasks, typical response time was about half a second, and volunteers quickly reached their peak performance. The trouble came when Marois showed participants an image, then almost immediately played them a sound. It appeared that if the second task is introduced within the half-second or so it takes to process and react to the first, it will simply be delayed until the first one is done. Delays progressively shorten as the interval between presenting the tasks lengthens.

There are at least three points where we seem to get stuck, says Marois. The first is simply identifying what we're looking at. This can take a few tenths of a second, during which crucial window of concentration we are incapable of seeing and recognising a second item. This limitation is known as the attentional blink. A second limitation is our short-term visual memory. This capacity shortage is thought to explain, in part, our astonishing inability to detect even huge changes in scenes that are otherwise identical, so-called change blindness. A third limitation is that choosing a response also takes brainpower. Selecting a response to one stimulus will hold back by some tenths of a second your ability to respond to a parallel one. This is called the response selection bottleneck theory, first proposed in 1952, and elaborated on by Marois and his colleagues in 2006.

But David Meyer of the University of Michigan has other ideas. Known as something of an optimist by his peers, Meyer has written papers with titles like 'Virtually perfect timesharing in dual-task performance'. His experiments have shown that with enough practice – at least 200 tries – some people can execute two tasks simultaneously as competently as if they were doing them one after another. Not all people manage this harmonious time-share, however, Meyer argues that individual differences come down to variations in the character of the processor – some brains are just more 'cautious', some more 'daring'. And contrary to popular belief, there are no noticeable differences between men and women. Meyer believes that it's not a central bottleneck which causes dual-task 'interference' but rather adaptive executive control which 'schedules task processes appropriately to obey instructions about their relative priorities and serial order'.

Marois's volunteers have also shown a huge improvement at managing concurrent tasks through regular practice. Where he disagrees with Meyer is in what the brain is doing to achieve this. Marois speculates that practice might give us the chance to find less congested circuits to execute a task – like finding trusty back streets to avoid heavy traffic on main roads – effectively making our response to the task subconscious. But while some dual tasks benefit from practice, others simply do not, according to Pierre Jolicoeur of the University of Montreal. Dual tasks involving visual stimulus and a motor response* (which he dubs 'in the eye and out the hand') and auditory stimulus with a verbal response ('in the ear and out the mouth') can, with enough training, be performed as well together as apart. He speculates that the brain connections they use may be somehow special, because we learn to speak by hearing and learn to move by looking. But pair visual input with verbal response, or sound to motor, and there's no such dramatic improvement.

For research purposes, these experiments have to be kept simple. Real-world multitasking poses much greater challenges. Needless to say, there appear to be no researchers who believe that you can safely drive and have a phone conversation. And according to results from a study at the University of Utah, even using a hands-free phone does not improve a driver's response time. The study confirms that what distracts a driver so badly is the very act of talking to someone who isn't present in the car and therefore is unaware of the hazards facing the driver. And the general preconception that we tend to get worse at multitasking as we age is borne out. In one study conducted by Art Kramer at the University of Illinois, for example, both young and old participants were asked to do a simulated driving task while carrying on a conversation. He found that while younger drivers tended to miss background changes, older drivers failed to notice things that were highly relevant as well, and likewise had more trouble paying attention to the more important parts of the scene.

However, Kramer also found that older people improved their performance with practice, and that brain scans showed that underlying that improvement was a change in the way their brains became active. While it's clear that practice can often make a difference, the basic facts remain sobering. For most of our history, says Marois, we probably never needed to do more than one thing at a time, so we haven't evolved to be able to. 'We have this impression of an almighty, complex brain,' he says, 'and yet we have very humbling and crippling limits.'

* motor response: a response that involves a muscular movement