0:00:01.969,0:00:03.759
spring fever

0:00:05.089,0:00:05.638
that's full of energy, vitality

0:00:06.144,0:00:08.404
and sexual appetite associated with spring

0:00:03.979,0:00:04.229
it's been written about for centuries

0:00:08.263,0:00:09.573
but does it really exist?

9:59:59.000,0:00:00.919
there's definitely something in this spring time air

0:00:00.919,0:00:04.919
a Canadian study showed a way that

9:59:59.000,9:59:59.000
teen pregnancy peaks in March,

9:59:59.000,9:59:59.000
right around spring break

9:59:59.000,9:59:59.000
and the another found that men

9:59:59.000,9:59:59.000
produce the most

9:59:59.000,9:59:59.000
and the healthiest sperm

9:59:59.000,9:59:59.000
in early spring

9:59:59.000,9:59:59.000
what's causing this seasonal shift?

9:59:59.000,9:59:59.000
Scientists think our increase in

9:59:59.000,9:59:59.000
energy and better mood

9:59:59.000,9:59:59.000
have to do with changes in hormone levels

9:59:59.000,9:59:59.000
an important one is melatonin

9:59:59.000,9:59:59.000
sometimes called the "sleep hormone"

9:59:59.000,9:59:59.000
it's released at night and helps us to fall asleep

9:59:59.000,9:59:59.000
when the nights are longer

9:59:59.000,9:59:59.000
we produce more melatonin

9:59:59.000,9:59:59.000
and in spring, as the night gets shorter

9:59:59.000,9:59:59.000
we produce less of it

9:59:59.000,9:59:59.000
may be explaining why we feel

9:59:59.000,9:59:59.000
more awake and more active

9:59:59.000,9:59:59.000
seratonin is another chemical

9:59:59.000,9:59:59.000
that affects our mood

9:59:59.000,9:59:59.000
it's known as the "happiness hormone"

9:59:59.000,9:59:59.000
and it's level risens in spring time

9:59:59.000,9:59:59.000
as it gets sunnier

9:59:59.000,9:59:59.000
and the pathologists think that

9:59:59.000,9:59:59.000
this changes in hormone levels

9:59:59.000,9:59:59.000
may have to do with survival and

9:59:59.000,9:59:59.000
reproduction

9:59:59.000,9:59:59.000
many animals lay low in the winter

9:59:59.000,9:59:59.000
using less energy because food is sacarce

9:59:59.000,9:59:59.000
early humans might have done the same

9:59:59.000,9:59:59.000
when food became more abundant in the spring

9:59:59.000,9:59:59.000
and it make sense that they become...

9:59:59.000,9:59:59.000
more....

9:59:59.000,9:59:59.000
active

9:59:59.000,9:59:59.000
not surprisingly

9:59:59.000,9:59:59.000
as you move toward the equator

9:59:59.000,9:59:59.000
spring fever disappears

9:59:59.000,9:59:59.000
for example

9:59:59.000,9:59:59.000
scientists have noticed that seasonal changes

9:59:59.000,9:59:59.000
and the birth rates of field mice

9:59:59.000,9:59:59.000
flatten out

9:59:59.000,9:59:59.000
as you get closer to the equator

9:59:59.000,9:59:59.000
but sunshine may not be the only

9:59:59.000,9:59:59.000
spring time "pick me up"

9:59:59.000,9:59:59.000
for humans, the optimal temperature for

9:59:59.000,9:59:59.000
good mood is 72ºF, and let's face it

9:59:59.000,9:59:59.000
once the temperature starts to rise

9:59:59.000,9:59:59.000
we're wearing a lot less

9:59:59.000,9:59:59.000
for Scientific American and Instant Egghead

9:59:59.000,9:59:59.000
I'm Yasmin Tayag