In 2002 people over the age of 65 made up 7 per cent of the world’s population

In 2002, people over the age of 65 made up 7 per cent of the world’s population. By 2050, that figure is expected to leap to 17 per cent.Among the many unknowns in these calculations, however, are two factors. The primary reason for this slowing, the Census Bureau said, is that fertile women of child-bearing age are a shrinking proportion of the overall population Largely, this is the result of people living longer. The world population is likely to increase to more than 9 billion by the middle of this century, roughly 50 per cent higher than it is now, according to a new study by the US Census Bureau.
But the exponential growth of the past 15 years is expected to slow significantly as some populations age and others are ravaged by Aids.The Bureau calculated that the world is currently adding population at a rate of 1.2 per cent per year. However, it is likely to take 14 years to reach 7 billion, a further 15 years to get to 8 billion, and another 20 years to reach 9 billion.

It took just 12 years for the population to jump from 5 to 6 billion – the fastest billion ever. At the prison-hospital in Fresnes, Esneault receives her patients in a cell decorated to not look like a cell, with colourful fabrics, photos, musical instruments, flowers and ornaments She herself is a sympathetic presence. Yet listen to her talk and you recognise the same phenomenon that Herz, Vermetten and others describe. “When people smell a particular odour, they are immediately overcome by emotion and pleasant memories from their childhood,” says Esneault.

“That strengthens their sense of self, and from that stems a sense of responsibility.”. In both cases, the odour stayed the same but people reported either pleasure or disgust depending on which label they saw They also behaved differently. If they thought the smell was sick, they said they wouldn’t go near it; if parmesan, they wanted to eat it.Not all smells detectable by humans possess this ambiguous quality. But the susceptibility of olfactory perception to distortion by visual or verbal information would seem to suggest an obvious therapeutic intervention, says Herz. Consider a rape victim who suffers a traumatic flashback each time she catches a whiff of the aftershave worn by the rapist – a popular aftershave worn by millions of men. The researchers’ interpretation was that the hippocampus plays a role in integrating information from the senses – information that the brain then uses to decide what it is perceiving.In December, Herz showed that this kind of hippocampus-mediated trickery can also elicit dramatically different emotional responses.

She asked people to sniff inside jars that contained ambiguous odours and had one of two labels attached. One odour was patchouli, which she called either “musty basement” or “incense”; another was a chemical combination she described either as “parmesan cheese” or “vomit”. So, they asked them to sniff vanilla and simultaneously showed them either a picture of ice cream or of cheese, while scanning their brains in an fMRI machine.People named the smells faster when the picture showed something semantically related to them, and when that happened, a structure called the hippocampus was strongly activated. “Some clinicians put a strip of vanilla or a strong, pleasant, everyday odorant such as coffee under their patients’ noses, so that they have this continuous olfactory stimulation,” says Vermetten. So armed, the patients seem to be better protected against flashbacks.