54 | New Scientist | 14 November 2020
Frizzy issue
I straighten my hair and my
friend curls hers with a heated
hair wand. Humidity, sweat or
washing instantly reverses the
process. My wavy hair goes frizzy
in humidity, but her straight hair
doesn’t. What is happening?Barry Stevens
The Trichological Society,
London, UK
Human hairs are hygroscopic,
meaning they absorb atmospheric
moisture. Stretching wet hair
shafts during a drying process sets
them into a desired configuration,
be that straight or curly. This is
fundamental to hairstyling.
It is a temporary structural
change though, only remaining
until moisture is absorbed,
whereupon the hair shafts return
to their natural state. Certain
hair types are more prone to this,
such as those with frizzy, finely
structured hair shafts. Hair that
has undergone thermal or
chemical processing, such as
relaxing, permanent waving,
bleaching or tinting, is also
more prone. These processes
compromise the structure of each
hair’s outer protective layer, or
cuticle, exacerbating permeability
and moisture absorption.Shedding tears
What is the biological advantage
of crying when emotional?Ad Vingerhoets
Tilburg University, The Netherlands
Tearful human emotional crying
evolved from the separation calls
or distress vocalisations made
by the offspring of all mammals
and several bird species when they
are separated from their mother.
Crying in animals is mainly
limited to vocal activity and to
infancy, but humans continue to
produce emotional tears for their
whole lifespan. When children
grow older, the importance of the
auditory component diminishes,
whereas the visible element – the
tears – gains prominence.Want to send us a question or answer?
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Full terms and conditions at newscientist.com/lw-termsThe back pages Almost the last word
JENNYDETTRICK/GETTYIMAGESHuman crying can be triggered
by many things. Lovesickness,
helplessness and grief are
significant antecedents
throughout life. Other triggers
change with age, reflecting
changes in emotional, cognitive
and social development. For
example, physical pain and
discomfort are often triggers
for infants and toddlers, but
tend to lose their importance
after late adolescence. On the
other hand, empathic crying,
which occurs in response to the
suffering of others, increases
with age. A similar pattern
is seen for tears triggered by
extraordinarily positive or
moving situations.
Tears help observers recognise
the need to provide support
and comfort. They are anevolved adaptation that promotes
helping behaviour in others by
inducing feelings of empathy
and social connectedness.Barbara Finlay
Cornell University, New York, US
Members of social species benefit
in many ways by communicating
their internal states to each
other. Recognition of need,
and consequent protection and
provisioning of weaker or younger
individuals, has been observed in
various primates, meerkats,whales and elephants outside
immediate parental bonds.
Humans, though, are
“hypersocial” and routinely help
injured or ill group members,
independent of age or relatedness.
Even the subjective experience
of pain and the performance
of^ “sickness” behaviour may be
amplified in humans in situations
like childbirth or viral infection,
compared with other less social
species. The descendants of those
who complained effectively and
received help are more likely to
be with us than those of the stoic!
But how do humans recognise
cries for help? In the absence of
obvious physical damage, what are
the main ways of communicating
pain and distress? Mammals
normally produce tears due to
chemical or physical irritation, but
humans also produce emotional
tears. These are part of a suite
of physical changes in humans
employed for communication.
Together, these changes
extend the avenues available to
communicate our internal states
and emotions. For example,
studies show that the addition of
tears to faces previously described
as sad made them seem sadder,
acting as an intensifier.
Of the many instruments
of the orchestra of expression,
tears come in at moments of high
intensity, pulling the observer
in more strongly.Michael Trimble
University College London, UK
Homo sapiens are the only living
species to cry as an emotional
expression. The development of
the capacity to cry in our hominid
ancestors depended on many
biological adaptations. These
include the development of the
facial muscles – especially around
the eyes and mouth – and the
size and connectivity of the brain
that allowed the development
of “theory of mind”: the ability
to recognise the behaviourThis week’s new questions
Seeing small What is the smallest animal with eyes and
could it see a molecule? George Illingworth (age 8), Louth,
Lincolnshire, UKNow is the time Buddhists recommend living in the present
moment. How long is this gap between the past and the
future? Derek Johnson, Moreton-in-Marsh, Gloucestershire, UKAre there any sighted
animals that are so tiny
they could see a molecule?“ Crying in response to
the suffering of others
increases with age,
as do tears triggered
by extraordinarily
moving situations”