How do we see a curved solid surface from a few sketchy lines on a page? From
ghostly images in the eye, we somehow perceive meaningful solid objects. Try
this for yourself. The “subjective” contours of the crater on this page do not exist
(see diagram).
Touch it and it feels flat. Your eyes, however, create a
detailed surface, a complex illusion with distinct zones.

These tricks are older than you might imagine. Donald Hoffman suggests that
“The prize for the oldest might go to a bracelet made of mammoth ivory . . .
dating from 22 000 BC. Its zigzag motif shows striking subjective contours along
the corners: runner-up might go to Palaeolithic cave drawings of bison, rendered
between 10 000 and 30 000 BC.”

This is the most striking chapter in a well-illustrated, excellently written
book, which should appeal to students and pundits of perception. Artists will
also be pleased by the notion that perception is a creative, intelligent
process.

In fact, what we do is receive signals from the physical realm, and then
create everything we see. Shape, size—all properties that we assign to the
world around us—are largely the result of our visual intelligence. Using
illusion after illusion, Hoffman shows us how to derive the rules that we use
unconsciously to construct the world from ghostly images falling on the retinal
cells at the back of our eyes. Our brain assumes that light falls from overhead,
for example, and so the “muffin pan” illusion fools us.

Indeed, it is a challenging thought (one appreciated by Newton), that there
are no colours in objects or in light, but that colour is psychologically
projected onto the outside world by the brain. And as colour squares show,
our perception of hues shifts and changes, depending on their context.

Hoffman’s lively discussion bursts with original ideas, some with their roots
deep in the past. His exploration of perception, for example, is inspired by the
work of the German polymath Hermann von Helmholtz. More than a century ago,
Helmholtz pointed out that the phenomena of illusions (the abnormal) can reveal
our perceptual processes (the normal). Visual illusions reveal solid information
about how we see, just as brain damage reveals much about an undamaged
brain.

So how do we see three dimensions from two? The suggestion is that the brain
adopts rules of perspective for seeing depth in the object world. This is the
reverse of what an artist does to represent depth, even though the geometrical
rules of perspective are a recent discovery of art.

No doubt the physical world is extremely different from how it appears; this
difference increases with every conceptual advance of fundamental physics. Our
technology, however, uses all our skills of visual intelligence to create worlds
for work and play. Playing a game of virtual basketball, for example, Hoffman
explains what is seen or perceived by those playing. All that he himself sees is
evoked by the rules of perception. And, he adds, although you may appear to
share an illusion—that is, several people may be taking part in the same
basketball game—the virtual world you are in is your own construct. You
are on your own there.

Mr M suffered the loss of his memory, this is the most famous and the most fully studied case in the history of neuropsychology. This is because it is the most complete, and the cause is clear. To relieve epilepsy, a surgeon removed the centre of Mr M’s brain. As a portion of Mr M’s brain was sucked out with a silver straw, so went his past, and with it all meaning of present and future. The surgeon had the grace and sense to confess to the disaster, and contributed to the study of the results.

In Memory’s Ghost: The Strange Tale of Mr M and the Nature of Memory, Philip Hilts recounts how for many years Mr M lived in a narrow window of time. With almost nothing beyond a few minutes of the past to make sense of the present, he could not anticipate or plan. Yet Mr M did have intellectual abilities – doing crosswords and very slowly solving the Tower of Hanoi problem, a logic puzzle – and he had a sense of humour, although of course the same jokes were repeated endlessly.

Observers reported episodes of self-destructive rage at his fate, which Mr M understood too well. He met the surgeon, and year after year he was investigated by distinguished scientists, including Brenda Milner and Suzanne Corkin, who conducted detailed tests to discover just what had been lost and what retained. Mr M’s massive brain oblation included bilateral loss of brain regions: the hippocampi and associated regions, as well as the amygdala. The hippocampi are two sausage-shaped structures within the brain. Both they and the amygdala form part of the limbic system, and are a buffer zone associated with short-term memory.

Hilts is not a medical doctor or a scientist. He is Washington correspondent and a lead reporter of the New York Times, specialising in health issues and science policy. He made extensive use of interviews with the psychologists studying Mr M, and with well-known experts on memory. And he spent some time with his subject.

I found this book to be a careful, intelligent account by a non-expert, but its weakness lies in oversimplified accounts of brain anatomy and physiology (with no diagrams) and of what the damage to Mr M means.

Of course, the published notes from luminaries such as Gary Lynch, Mortimer Mishkin, Whitman Richards, Roger Schank, Larry Squire and Endel Tulving are interesting in considering the nature of memory.

The main findings from the case of Mr M and other less clear-cut cases is that the hippocampus and amygdala brain structures are vital for memory, that damage to both sides of the brain has devastating effect, and that there are many kinds of memories.

Besides long-term and short-term memory, there are separate “memory engines” for skills, general impressions and specific facts. The point is that each form of memory may separately be lost, some disappearing with specific regions of brain damage or loss. This leads naturally to the view that each kind of memory has its own module separate from the others. No doubt this is largely true, but it is easy to fall into the phrenologist’s fallacy.

Phrenology was founded by the reputable anatomist Franz Gall late in the 18th century. His notion was that human abilities are localised and, when highly developed, could be felt as “bumps” on the skull caused by locally increased brain size. Phrenology ignored the interdependence of brain regions and functions.

The advocates of phrenology assumed that it is recognisable abilities and character traits that were localised. Is this plausible? For anyone with experience of electronics, neither assumption is likely to be true of complex systems. If you change one bit, odd things happen elsewhere, often producing “symptoms” that are difficult to explain. Again, software bugs may have bizarre effects that show up in only special conditions or situations. Indeed, it is logically impossible to localise function if we don’t know what the functions are – in this instance, how the brain works. So, surely, we need a theoretical neurology?

The other side of this coin is that cases such as Mr M provide invaluable data for isolating some functions and gaining theoretical insights into how the brain works. The difficulties are that loss of a bit of brain may not remove a single function and, if it did, the rest of the brain may compensate. There may also be redundant systems – much as we have two lungs. Losing one lung, may make many activities difficult but the patient survives. So nothing may happen, at least under usual conditions, as a result of extensive brain loss.

Mr M did suffer such a loss on a vast scale. What seems amazing is that the psychological losses were not more general. If he had suffered from depression, for example, we might consider explaining the memory losses in terms of lack of motivation but this seems inappropriate. It does look as if Mr M just lost memory, and undoubtedly this is of great scientific interest.

Mr M did not lose the ability to learn and remember motor skills. What was lost may be particularly associated with consciousness. Learning a skill, such as riding a bicycle, is not conscious: it is not necessary or indeed possible to remember each event leading to the acquisition of such skills. And these memories of motor skills are evidently stored in different brain regions from particular memories. Motor skills seem to be stored very generally in the brain.

When Oliver Sacks describes his cases of neurological damage, we hear the voice of a dedicated expert. Perhaps we learn as much about Sacks as about his cases, but it is a rich, wonderful mix, full of theoretical underpinnings. Hilts’s Memory’s Ghost is very different because it is almost totally lacking in theoretical backdrop. This sometimes makes it seem naive, for example about memory drugs, and the relationship between structure and function. And it leaves the book open to some sillinesses. I found a small mistake in the Gregory and Wallace case of SB, who gained his sight when an adult after infant blindness: he could not and did not use a lathe before the operation.

A different silliness lies in Hilts’s complaint that this important research material is locked up in impenetrable prose, in obscure learned journals. On the face of it, he has a point: it is difficult to find, difficult to understand. But data are of little use when they are not interpreted and may be misused scientifically when wrongly interpreted.

Sacks, Alexander Luria, and a tiny handful of other neuroscientists, have done great service by making their scholarship, their experience and insights available to a surprisingly wide readership, from medics to philosophers and lay readers. One would indeed like to share more of the experiences of those who have spent many years of their professional lives devoted to understanding holes in the head. Semipopular books by scientists reveal their working assumptions, and their hunches and difficulties help the next generation to grasp both the problems and the solutions. There is nothing of this here: the author is correct to hint that it should have been written by an involved, literate scientist.

Switzerland is marking its 700th anniversary with a celebration of science
and technology. Just outside Zurich, people walk in the sky in a fairy kingdom
of tents and towers rising above the lake. There is less than a month left
to share this miracle as Heureka closes on 27 October.

Masterminded by Georg Muller, whose earlier exhibition, Phenomena, was
a triumph of the hands-on movement, Heureka is an inspiring concentrate
of more than 300 Swiss research projects, set in the context of world science
from the Egyptians, the Greeks and0 Roman engineering to the latest discoveries
and the newest technology.

More than a 1000 scientists from Swiss universities and polytechnics,
engineering colleges and private research institutes have contributed their
experiments, knowledge and ideas. Many distinguished scientists make themselves
available daily to explain what they do and for the public to question and
discuss it – to share science.

There is due emphasis on Swiss life and needs for the future. A major
section concerns the best use of the limited available land, with voting
options for various kinds of private ownership in town and country and the
implications of each choice, given a continuing rising birth rate (half
the population is Catholic). Another example is the zero energy house, which
has significance for many other countries.

Of Heureka’s aspirations and inspirations, Muller says: ‘The aim is
to provide information but above all to encourage dialogue between scientists
engaged in research and interested laymen.’ He adds: ‘It is essential that
sound common sense is not underestimated by the specialists nor current
research rejected due to prejudice’.

There is also a practical commercial underpinning, as the president
of the Research Interest Group, Professor Alfred Pletscher explains: ‘Our
economy has made its mark time and again in international markets by virtue
of its convincing achievements (which) would not be conceivable without
dynamic research activity on the part of public and private institutions’.

For the most part these achievements are not appreciated by the public.
The only sadness is that the message will soon fade away, following the
undoubted impact of this truly remarkable exhibition. It is no less than
a national statement of commitment to the principles and responsibilities
of science.

Heureka is a crescent of eight huge, wonderfully shaped tents, providing
19 000 square metres of exhibition space, with central masts 30 metres high
that can be climbed by a spiral staircase or in a lift. The central four
are linked by dizzying suspension bridges, so one literally walks in the
sky.

An extraordinary richness of science and technology is represented.
A Swiss contribution is the 18th-century mathematician Leonhard Euler’s
skeletal structure, which rises as a charmed snake from a small box to become
a tower the height of a person when released by a single central string.
It is now used to deploy aerials in space craft.

One of the most striking demonstrations relies on chemistry from Ciba-Geigy
to produce computer-generated models you can handle and use. Stereolithography
works by ultraviolet light solidifying a liquid polymer. When the light
comes from computer-controlled laser beams it can be used to form objects
that can be made in no other way, such as prototypes for engineering designs
and mathematical wonders such as Klein bottles. The pure magic of producing
actual objects from computer graphics was not lost on the visitors, who
stood entranced.

The science of other countries, including Britain, is well represented
from Isaac Newton and Charles Darwin, to Roger Penrose’s tiles forming endless,
never-repeating patterns. These are magnetic, on a large wall, and (psychologically)
attract creative activity from visitors of all ages.

Near the great tents is the Galileo Tower, made from 825 tonnes of wood
donated free by Swiss villages. A sloping ziggurat-like ramp 300 metres
long leads to its top and a rewarding view of the lake. Here we find vignettes
of science from all countries: a martyr’s pyre for Giordano Bruno, a huge
Archimedes screw lifting water with a human hamster wheel, construction
of a Roman road, Leonardo’s mechanical bird, an alchemist’s laboratory with
live chemistry demonstrations and much more.

The burning question is: does the public enjoy, and sufficiently understand,
this aesthetically appealing but in places technical exhibition? Doubt was
cast in Nature by Steven Dickman in the article ‘Frustration in Switzerland’
(20 June). He reported that visitors were baffled: ‘We saw everything but
understood very little,’ and so on. This was written when Heureka first
opened, and was not fully running. We formed a rather different impression.
Attendance has been running at about 5000 visitors a day, 60 per cent of
whom are children, mainly in school parties in the mornings; Sundays visitors
are families, most of whom are adults. We were struck by the obvious interest
and involvement of the visitors. This was especially so when human explainers
were performing.

Some of the most technically sophisticated displays – such as the tunnelling
electron microscope, which was exceptionally well explained with working
models – were the most popular.

No doubt much is opaque to nonscientists. But given the level of obvious
excitement and interest, does this matter? Everything is opaque (or invisibly
transparent) before one learns to see. During its far too short life Heureka
is opening eyes and minds to the past and future of science.

Richard Gregory is president of the Exploratory, Bristol, and emeritus
professor of psychology at the University of Bristol. Priscilla Heard is
research fellow at the University of Bristol and lectures at Cheltenham
and Gloucester College of Higher Education.