Legislation allowing 16 and 17-year-olds to vote in the Scottish independence referendum began its long passage through the Holyrood legislative machine yesterday.

Is extending the franchise in this way a good idea, can it be achieved without damaging logistical problems and could the votes of these teenagers be decisive in deciding Scotland's future?

Deputy First Minister Nicola Sturgeon declared yesterday that the franchise was being extended to "those with the biggest stake in Scotland's future". It shows what a complex issue this is.

Strictly speaking, babes in arms are the Scots who will live with the consequences of the referendum result for the longest yet nobody is suggesting giving them the vote. Clearly a balance has to be struck between extending the franchise as widely as possible and giving it to those mature enough to understand the issues.

It is true Scottish 16-year olds can pay tax, enter employment and marry without parental consent. On the other hand, nobody is suggesting the right to buy alcohol should be extended to 16-year-olds or the right to fight on the front line and die for their country. There are different thresholds for different activities and rightly so in an era where neuroscience suggests the parts of the human brain we use to weigh up the consequences of our actions often do not mature properly until around the age of 20.

In the vast majority of the world's democracies, there is a consensus that 18 is the right age for the franchise. Some European countries are contemplating lowering the voting age but The Herald has argued that this should happen only after a full consultation and extensive trials, such as those currently being piloted in municipal elections in Norway. If change is deemed desirable, it should be extended to all elections local and national. The referendum is too serious an issue to be the subject of an experiment.

By introducing voting at 16 only for the referendum, the SNP risks accusations of seeking to influence the poll, though in fairness the party has favoured lowering the voting age for many years. Besides, constitutional experts and psephologists appear to agree that enfranchising a group that constitutes less than 3% of the electorate is unlikely to materially affect the result (partly because younger age groups are less likely to vote).

There are obvious advantages in bringing 16 and 17-year-olds on board. Because most live at home with parents, they should be easier to find and register and the very act of registration may help to engage them in politics.

The challenge now is two-fold: first, the Scottish Government must fulfil its pledge to keep this data separate and secure. Otherwise, there is a risk that these youngsters will be bombarded with hard-sell marketing messages. Secondly, having offered the vote to every 16 and 17-year-old on the day of the poll, it must make sure the registration process is comprehensive. This is more of an issue for future 16-year-olds, rather than older teenagers, who can already register as "attainers". Gaps in registration risk exposing the Government to court cases under the Human Rights Act. The die is now cast. Regardless of age, now it is time for voters to get beyond procedural detail and focus on the substantive issues.