9 November 2019 | New Scientist | 25Want to get in touch?
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newscientist.com/lettershe calls an “attention schema”. In
an earlier issue, Donald Hoffman
explained how we may see the
world as a series of “icons” that
represent real objects in the world
but aren’t those objects, because
if we saw an object for what it was,
we would be overwhelmed by its
complexity (3 August, p 34).
An attention schema is a model
of attention that our brains can
manipulate to shift focus from one
object to another, without having
to worry about all the details of
synapses and neurons that are
actually the basis of our attention.
It seems to me that these two
ideas are related. Graziano’s
attention schema is one of
Hoffman’s icons.
We experience the attention
schema as consciousness. We
could say consciousness is an icon
that represents us to ourselves. It
gives us the ability to manipulate
objects and find pathways
through an environment.
If neurobiologists one day
understand how our brains
generate Hoffman’s icons, they
will be close to knowing how our
brains generate consciousness.
Apps won’t reliably spot
mental health symptoms
28 September, p 7
From Miles Clapham, London, UK
Jessica Hamzelou reports on a
smartphone app that could spot
signs of schizophrenia in facial
expressions and speech. This may
be confounded by the fact that
medication, notably neuroleptics,
can alter voice and facial
expressiveness. Alcohol and other
drugs can have similar effects.
A bigger issue is the notion
that schizophrenia is a single
illness distinguished from other
conditions by such signs. Reduced
facial expression and altered voice
and content of speech can be
part of many emotional and
psychological problems. Shyness
might also produce these effects.
The notion of smartphone
surveillance as a way of monitoring
people’s mental health, even with
formal consent, is worrying.
We should instead rely on key
relationships with mental health
staff, which we know help in many
ways other than just monitoring.
Phone surveillance seems like
one more blow to the idea that we
should develop humane services
based on understanding people
in their social context.Carry on with life on your
solar-powered airship
12 October, p 15
From David Wyper, Glasgow, UK
I enjoyed reading Donna Lu’s
article on a solar-powered airship
scheme while my wife Margaret
and I returned to Glasgow from
New Scientist Live. It concludes
with the view that low speeds
would be a deterrent to using
airships for passenger transport.
Instead of our 5-hour rail trip,
we could have travelled by air in
1 hour. Eco-anxiety prompted us
to take the train. While perusing
the article, it occurred to me that
our decision hadn’t cost us any
time. We were doing what we
would have done at home: reading,
listening to music, emailing,
chatting and eating snacks.Sunscreen formulators
still have work to do
27 July, p 20
From Brian J. Wilkins,
Wellington, New Zealand
As midsummer approaches
here, I return to Jessica Hamzelou’s
report that, of the 16 active
ingredients for sunscreen
listed as “safe” in the US, only
zinc oxide and titanium dioxide
are certainly safe and effective.
After nearly 40 years of research
into sunscreens, I note that the
medium for the active ingredient
is also important. Most sunscreens
are oil-water emulsions usingsurfactants, which help the
passage of substances through
the skin. A small number are
surfactant and water-free. These
tend to be greasy, but avoid the
problem of emulsion-based
sunscreens washing off, which
makes a mockery of their sun
protection factor ratings.
Zinc oxide and titanium
dioxide have their own problems.
The finest particulate sizes have
the least whiteness on the skin,
but have run up against studies
confirming that they can enter
tissue and do damage. Larger
particles are safer and good
blockers of ultraviolet light, but
require users to look like white-
painted circus clowns. Sunscreen
formulators still have work to do.Lack of funding leaves
satellite data inaccessible
21 September, p 10
From Alan Trusler,
South Ockendon, Essex, UK
You report findings on the melting
Greenland ice cap. Many amateur
scientists and school pupils have
witnessed this. In the mid-1970s,
I worked on remote sensing in
science education.
But the closure of Dundee
Satellite Receiving Station due
to the withdrawal of funding
has left us without data from
polar-orbiting weather satellites.
The other UK-funded satellite
receiving station at Plymouth
doesn’t offer such data.Yet another problem with
electrolysing seawater
Letters, 12 October
From Tim Stevenson,
Prestwood, Buckinghamshire, UK
Clive Semmens discusses
ways to get around obstacles to
electrolysing seawater to make
hydrogen. But electrolysing a saltsolution is the standard way
of making bleach.
Sodium hydroxide and
hydrogen are produced at the
cathode and chlorine at the anode.
Reacting sodium hydroxide and
chlorine produces sodium
hypochlorite. Using seawater
to produce hydrogen would be
complicated by these reactions.Cyclists don’t need or
use gyroscopic effects
Almost the Last Word, 5 October
From Tim Lewis,
Narberth, Pembrokeshire, UK
Several answers in Almost the
Last Word refer to the gyroscopic
effect of bicycle wheel rotation
helping to maintain balance.
This has been discussed before
(Last Word, 9 December 2006 and
3 February 2007). Michael Brooks
reported experiments showing it
to be false (28 May 2011, p 44).
Balance on a bicycle is
maintained solely by continual
correction of rider and handlebar
positions. The faster you go, the
smaller the corrections you
have to make.From Stephen Kinsella,
Kingston Bridge, Somerset, UK
The gyroscopic action of the
wheels is negligible in balancing
a bicycle. Think of a child’s scooter
with its tiny wheels, or an ice skate
with no wheels at all.
Balance is achieved by the rider
constantly moving their centre of
gravity slightly to one side or the
other. To stay stationary, a rider
moves slightly back and forward,
as well as shifting side to side. This
is observed with unicyclists. ❚For the record
❚ There is at least one other
rearrangement of a dartboard
in which each neighbouring pair
adds up to a square number: 20,
18, 15, 10, 6, 19, 17, 8, 1, 3, 13,
12, 4, 5, 11, 14, 2, 7, 9, 16 (Puzzle,
28 September; solution, 5 October).
❚ Tardigrades, or “water bears”,
have eight legs (12 October, p 34).