Wednesday 30 June 2010

A membrane-enclosed outgrowth of the brain

"The eye is unique, both as a membrane-enclosed outgrowth of the brain... '' 

Ionic control of ocular growth and refractive change. Sheila G. Crewther, Helena Liang, Barbara M. Junghans and David P. Crewther. PNAS October 17, 2006 vol. 103 no. 42 15663-15668 

From a developmental perspective the eye is an outgrowth of the brain. During fetal development small patches on the outside of the embryo develop into the two eyes.

... an effortlessly natural extension to the eyes and the hand

British naturalist Sir John Lister-Kaye has recently published a fascinating book-long rumination on wildness. The book is based on daily journals kept by Kaye describing the same circular walk from his home in a glen in the scottish highlands up to a small hill loch. One of his essential companions on these walks is a battered pair of Swarovski binoculars, which he descibes as follows;

"Good binoculars are to a field naturalist as a set of spanners is to a mechanic, a stethoscope to a doctor. They must be clear, sharp and an effortlessly natural extension to the eyes and the hand. They are a vital, silent route to where you want to be."

At the Waters Edge; A personal quest for wildness. John Lister-Kaye. Canongate Books. 2010.

John Lister-Kaye comes from a long line of landowners and business leaders. He has an interesting life story, that expains how and why he ended up as a naturalist (Wikipedia has a good entry on him). He has run the Aigas Field Centre in the highlands of Scotland since 1977.

... drawing disciplines the eye and brain, tempers judgement, and makes the hand responsive.

From the Rhode Island School of Design statement of foundation course elements.

In the drawing studio you will work with the development of skills in perceptual drawing, formal visual principles, and abstract thought. Taught by means of the human figure, landscape, still life, or theme, drawing disciplines the eye and brain, tempers judgement, and makes the hand responsive. You will explore form as it pertains to representation and the organization of surface through line, shape, light, texture, and space. At RISD, drawing is considered the basic tool of all art and design disciplines, reflecting the conviction that this skill "the coordination of eye, hand, and brain" is essential to the way the painter, sculptor, architect, or designer creates.

This  is a fabulous statement about the role that drawing plays in Intense Seeing.

Study of a Peacock Feather, 1873. John Ruskin

Tuesday 29 June 2010

The Ecological Fallacy & MAUP

The ecological fallacy occurs when analyses that are based on grouped data lead to conclusions that are diļ¬€erent from those based on the analysis of individual data. One of the early examples is given in Robinson (1950). 

From the Wikipedia entry;
`An ecological fallacy (or ecological inference fallacy) is an error in the interpretation of statistical  data in an ecological study, whereby inferences  about the nature of specific individuals are based solely upon aggregate statistics collected for the group to which those individuals belong. This fallacy assumes that individual members of a group have the average characteristics of the group at large...'

(on Robinson 1950) 

`...for each of the 48 states in the US as of the 1930 census, he computed the literacy rate and the proportion of the population born outside the US. He showed that these two figures were associated with a positive correlation of 0.53 — in other words, the greater the proportion of immigrants in a state, the higher its average literacy. However, when individuals are considered, the correlation was ?0.11 — immigrants were on average less literate than native citizens. Robinson showed that the positive correlation at the level of state populations was because immigrants tended to settle in states where the native population was more literate. He cautioned against deducing conclusions about individuals on the basis of population-level, or "ecological" data'

This is closely related to a problem that I have been aware of for a long time under the name of "change of support problem" - which is how it is known in the field of mathematical morphology and integral geometry. I recently found out that within spatial statistics and GIS it has another special name; Modifiable Areal Unit Problem (MAUP). The basic problem is that for spatial data, such as Health outcomes recorded by zip-codes or counties, socio-demographic data from Census tracts, safety or health exposure estimates within a region of suspected source etc etc, statistical inference changes with scale.

A classic early paper is Gehlke and Biehl (1934) who found that the magnitude of the correlation between two variables tended to increase as districts formed from Census tracts increased in size.

Waller & Gotway (2004) describe it as a "geographic manifestation of the ecological fallacy in which conclusions based on data aggregated to a particular set of districts may change if one aggregates the same underlying data to a different set of districts".

The paper by Openshaw and Taylor (1979) described how they had constructed all possible groupings of the 99 Counties in Iowa into larger districts. When considering the correlation between %Republican voters and %elderly voters, they could produce "a million or so" correlation coefficients. A set of 12 districts could be contrived to produce correlations that ranged from -0.97 to +0.99.

From Openshaw (1984);

`the areal units (zonal objects) used in many geographical studies are arbitrary, modifiable, and subject to the whims and fancies of whoever is doing, or did, the aggregating.'

below is an example figure from Openshaw (1984).


Gehlke, C. E. and K. Biehl (1934). Certain effects of grouping upon the size of the correlation coefficient in census tract material. Journal of the American Statistical Association, 29, 169-170.

Openshaw, S. (1984). The Modifiable Areal Unit Problem. CATMOG 38. ISBN 0 86094 134 5

Openshaw, S. and P. Taylor (1979). A million or so correlation coefficients. In N. Wrigley (Ed.), Statistical Methods in the Spatial Sciences, London, pp. 127-144. Pion.

Robinson, W. S. (1950). Ecological correlations and the behavior of individuals. American Sociological
, 15, 351–357.

Waller, L.A. and C.A. Gotway. 2004. Applied Spatial Statistics for Public Health Data. Hoboken, NJ: John Wiley & Sons. 

Tuesday 22 June 2010

Feynman Page Layout

Richard Feynman is justifiably famous for many things - including a set of Physics textbooks he published in 1964. These are incredibly dense and well written. They also have excellent page layouts. Here is an example.

Monday 21 June 2010

Daniel Danger Video

A very interesting 45 minute video of Daniel Danger on his website.

“theres nothing out there, I do not hear what you hear”. Ten colour screenprint 2008

Sunday 20 June 2010

Hilbre from the Dunes

Sunday 6 June 2010

Q: What did 1015 Sunsets ever give us? A: Eyes.

This is a profound statement from Prof Ronald Fernald of Stanford.
"Light has probably been the most profound selective force to act during biological evolution. The 1015 sunrises and sunsets that have taken place since life began have led to the evolution of eyes which use light for vision and for other purposes including navigation and timing. Although eyes occur in a variety of shapes, sizes, optical designs and locations on the body, they all provide similar information about wavelength and intensity to their owners."

Fernald, R. D. (2000). "Evolution of eyes." Curr Opin Neurobiol 10(4): 444-50. The file is here = PDF

[NOTE added 25/11/2011. Since posting this I went and re-checked Fernald's estimate and it is wrong by 3 orders of magnitude. I estimate that there have been 1012  sunrises and sunsets, not 1015 .] 

Thursday 3 June 2010

It's a Map

An extract from a book about maps - an Ojibwe map from ca. 1820 in Making Maps
A Visual Guide to Map Design for GIS. John Krygier and Denis Wood. ISBN 978-1-59385-200-9