New Scientist - USA (2020-03-28)

54 | New Scientist | 28 March 2020

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The back pages Almost the last word

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Night watch

The health-tracking watch I got

for Christmas claims to know

when I am awake or in light, REM

or deep sleep. How does it do this?

James Olver

By email, no address supplied

I have been the proud owner

of a health-tracking watch for

just over a fortnight, and it has

become clear to me that it isn’t

very good at knowing whether

or not I am asleep.

Several times, it has reported

that my night’s sleep started

significantly earlier or finished

significantly later than was the

reality. It appears to interpret

a period of low, stable heart

rate, together with little or

no movement, as light sleep,

provided it is followed or

preceded by actual sleep.

It has overestimated my period

of sleep by more than 2 hours

on a number of occasions. These

events have happened when I have

yet to go to bed, when I am in bed

but have yet to fall asleep, when

I have woken at night and been

unable to get back to sleep, and

even when I have got up but then

sat quietly for some time.

A major reason for buying the

device was to monitor my sleep

in an effort to improve my very

poor sleep patterns. My initial

impression after two weeks is

that it isn’t fit for purpose.

Rowan Hooper

London, UK

I looked into this for the chapter

on sleep in my book Superhuman:

Life at the extremes of mental

and physical ability. I spent the

night in a sleep lab wired up to

an electroencephalograph (EEG),

which directly measures brain

waves, but I was also wearing a

sleep tracker.

The sleep tracker, like most on

the market, measured heart rate

and movement. The idea is that

because, for example, the heart

slows as you move into stage 2

(deep sleep) of our four-stage sleep

cycles, and the body is paralysed

during REM sleep, the tracker can

estimate the stage you are in.

The EEG, however, measures

brain waves, so it can categorically

show the stage of sleep you are

in. The picture the sleep tracker

provided of my sleep cycle wasn’t

the same as the very accurate

picture that came from the EEG.

In other words, sleep trackers

guesstimate the stage, and might

be less reliable than direct

measurement with EEG. If they

can help you improve the quality

of your sleep, great. If they add

to the anxiety over the quality of

sleep you think you are getting,

perhaps not so good.

Allan Angus

via Twitter

I have used a sleep tracker for

around five years. Subjectively,

I would say its results correlate

well with my feelings of being

well rested or not. Over the years,

it has also collected data that

indicate an improvement after

my kids stopped needing a ride

to school in the morning.

Seat of wisdom

Have we always known that

we think with our heads? Is

it instinctive?

Hazel Russman

London, UK

We haven’t always believed that

we think with our heads. The

ancient Egyptians had such a poor

opinion of the brain that, during

the process of mummification,

they removed it through the

nostrils and threw it away.

In ancient times, Jews

associated each mental function

with a different part of the body.

Emotion was located in the

bowels, willpower in the heart and

intellect apparently in the kidneys.

Thus, in literal translations of the

Bible, Psalm 16, verse 7 says: “I will

bless the Lord who has given me

counsel. My kidneys instruct me

in the night season.”

Peter Urben

Kenilworth, Warwickshire, UK

Sceptics, and those of like kidney,

know in their heart that many

mental attitudes and activities

are linguistically attributed to

organs far from the head. Some

of the examples we can put a

finger on are purely metaphorical,

but many must reflect an earlier

view of physiology.

Spencer Weart

Hastings-on-Hudson, New York, US

Brain trauma – as many warriors

must have noticed since ancient

times – can cause cognitive

disorders. In particular, a blow to

the head, far more than anywhere

else, can render us unconscious.

So, naturally, the acute observer

Aristotle, and his academic

followers for some two millennia,

concluded that the brain is an

organ to cool the blood, and the

seat of intelligence is the heart...

wait, what?

Eric Kvaalen

Les Essarts-le-Roi, France

In the Bible, there is no mention

of the brain, or of thoughts being

in the head. Instead, thoughts

and emotions were considered

to be associated with the heart (for

instance, Deuteronomy, chapter 6,

verse 5), the liver (Lamentations 2:11

and the original text of Psalm 16:9),

the bowels (Psalm 40:8) and

even the kidneys (Psalm 26:2).

Some translations don’t bear

this out though. ❚

This week’s new questions

Mysterious alignment How can ancient monoliths that were

aligned with the sun at the equinox thousands of years ago

still be lined up, given that plate tectonics moves land masses

over the years? Roger Bennett, Mansfield, Nottinghamshire, UK

Material change What kinds of plastic are the most planet-

friendly? And are biodegradable materials, such as those

made from bamboo, preferable to recycled plastic, which

makes use of the plastic waste that we already have?

Lynsey Harrison, Leeds, UK

How are these stones

still aligned with the

sun after all this time?