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Tom,

yet again, excellent questions.

> Why the axial line?
>
> Thank you to everyone for the fulsome replies to my little
> question.  In my various sporadic contacts with the Spacesyntax
> community I have noticed great generosity in dealing with
> dabblers like myself.    (Incidentally, the three people I
> remember being most vehement in their distrust of spacesyntax
> were all former Bartlett students of architecture    what do you
> do to them?)
>
> On Sat, 10 Feb 2001 Alan Penn <[log in to unmask]  wrote:
>  Well - in the light of what I've said above, it should be clear
> that a curve can be represented by a direct connection, if that
> is what you are trying to represent, and so long as you are being
> consistent. The question is, if I represent it one way (direct
> connection) or another (broken up somehow) which version of the
> analysis tells me something interesting (for instance, which
> correlates best with an observed human behaviour or what ever).
> The choice of representation is part of the analysis, but the
> empirical data about the world 'talk back' and tell you which one
> to think about. This is just the beginning of course. If, say,
> the connected version correlated best with movement, you are now
> left with a new and more interesting question, that is 'why?'.
> This is why I think the question 'why the axial line?' is the
> more interesting question.
>
> This paragraph seems to get to the heart of my confusion over
> procedure.  You say that spacesyntax is a theory (or theories)
> about the effects of space on society which are falsifiable.
> Doesn't this mean that you postulate a causal mechanism between
> features of the world and the phenomena being studied (observed
> human behaviour)?  The mechanism allows you to predict what type
> of behaviour will be observed in another situation which is not
> obvious from the first (non-trivial difference).  It also
> specifies  _exactly_ which features are relevant and must be
> measured or recorded.
>
Not quite - I was careful to say "effects of space on society" _not_
behaviour. No doubt the mechanisms could pass through behaviour, but the key
hypotheses that I am thinking of are about social factors. For instance, the
patterns of movement entailed in different jobs in a hospital, their time
structures and the effects of spatial pattern on those movements leads to
different patterns of co-presence in space between doctors, nurses and
patients. Some of these user categories are more often together in certain
spaces, others are systematically kept apart. Movement behaviours are
clearly involved in this, and I think that the effects of spatial pattern on
movement behaviour would be entailed in any mechanism, but the kind of
hypotheses I am thinking about have been about the social effects of
buildings on creation and control of interaction or social reproduction
amongst different groups in an institution.

The position with regard behaviour is slightly different. We know that
integration in the axial map is pretty robustly correlated with observed
movement flows of the whole population, given certain provisos about
relative homogeneity of land use and development density, and of the
intelligibility of the configuration. This is an empirical fact, and
certainly 'falsifiable' - we might discover a class of settlements or
cultures in which this correlation did not hold. We just havent so far.
Bill's 'theory of natural movement' might appear to be about behaviour, but
I would hold is almost exactly the opposite. It is about the triad of
movement, configuration and attraction, and proposes that configuration
comes first, that an underlyong pattern of movement results, that land uses
of different attractivness then locate themselves to take advantage of that
movement, and preferentially attract people to those locations thus creating
a multiplier effect. An attractive feature of this scheme is that it avoids
any environmental determinist assertions at the level of the individual. It
does not say that an individual 'john' will turn right at the end of the
street, but that the whole population will be distributed some way. It is
really the fear of making determinist assertions that leads me to fight
rather shy of claiming effects of space on behaviour except at the group /
social level of aggregation.

That does not mean that there are no such effects - I think that there must
be - but just at the moment we do not understand the mechanisms.

> If you try different representations until you find a
> correlation,  surely you are searching FOR a mechanism, not
> applying one.  And you might find that the axial integration
> correlates with the number of peppermints eaten by the researcher
> - probably not a causal relation!

No that's not quite the way to see it either. The representation that is
found to relate consistently (and for which plausible mechanisms exist) can
still be the result of a search process. It is important to be clear about
the statistics here. If you take a string of numbers - say the counts of
people walking along streets in an urban area, and then use a random number
generator to make another column of numbers, if you do this repeatedly then
eventually you will get a correlation to some level of error (say and r=.7)
The fact that you have done this tells you nothing. If however, your random
number generator goes on to give you another column which also correlates to
that sort of level, and another and another, you would have to infer that
not only was the random number generator flawed, but that it was flawed in a
very intersting way. In just this way if all one found was a correlation
that would tell us nothing more than that statistics was working. The
interesting part is when we find that a particular representation repeatedly
correlates. There is nothing in this process to stop one doing lots of
searching for a pattern, it is that finding a pattern just once is not
enough.

> You say that a curve can be
> represented by a straight link "if _that_ is what you are trying
> to represent"; but what is "that"?  Presumably it is some
> mechanism by which physical features cause variations in human
> behaviour;  but _what_ mechanism?

If I remember you right you were describing a path that curved but where you
could see to the other end - I take the 'that' to be the fact that you can
see to the other end and so think it justified to consider it as connected.

>
> In talking about finding a suitable representation  for a
> problem,  you seem to be dealing with a problem which has two
> variables (probably independent ones).  You do not know what it
> is that is affecting people s behaviour (is it configuration in
> this instance?), and you also do not know what combination of
> environmental features reliably  generate particular behaviours;
> so how can you make falsifiable predictions?
>
Well, what we know is that there are very regular correlations between
spatial configuration and movement under certain conditions - we do not know
why this is so. But the principle that the correlation exists is eminently
falsifiable. All you have to do is observations, some spatial analysis, and
show that the correlations do not exist. That the times that we have
observed this were somehow flukes.

> Kuhn refuted Popper?   Well the scientific method still gets
> along in an empirical sort of way doesn t it?  I understand it is
> usual to undertake experiments where there is only one
> uncertainty.  This allows you either to discover whether
> particular measurable features cause predictable changes in
> something else, OR to predict the phenomena of the real world
> from the set of causes which appear to be present (or vice versa)
>
> I seem to be  teaching my grandmother  here   I haven t even
> completed a research degree   and doubtless the relevant
> mechanisms for Spacesyntax have been worked out over the last
> twenty five years, but it is not very evident from the
> publications.  Are the mechanisms kept in the background for fear
> of frightening the public?  Or are they implicit in the
> accumulated wisdom at UCL?

No it is that we dont really understand the mechanisms yet. Virtually
nothing is known for instance about cognition of space - lots of hypotheses,
but nothing well validated. Against this background it would be very unwise
to postulate 'mechanisms' that say how space leads to behaviour. This doesnt
mean that we dont have some hunches about what might be happening - these
are the hunches that guide the research - it is just that you dont often
publish unsubstantiated/untested hunches.

>
> I really think it is here that spacesyntax (as published) lacks
> clarity.  The measurements made are technical and hard to
> understand; as you say, this is the nature of science.  The
> behaviour studied is controversial and open to argument - only to
> be expected.  It is the casual mechanisms between them which are
> interesting,  which might be understood at a 'popular level , and
> which is able to provide evidence for the importance of spatial
> configuration which ordinary mortals could appreciate.

All you are asking is that we get on with the science... It is not that we
are 'holding back' a deeper understanding that we all have but wont let out
to the lay public. If our writing is unclear that is because our
understanding is unclear.

>
>
> I am interested to hear that  minimum axial line  maps can be
> generated by computer from the all-line map.  I gather this is
> not done in practice,  since the all-line software has not been
> updated for modern machines.   However, this rather misses the
> important question of what information goes INTO the maps.  Alan
> says that measures are generated from a dxf file of a plan, but
> unless you know what EXACT features cause the behaviour of
> interest, how do you map the right thing?

Another instance of the answer being when you know what to map. This is why
you map it as many ways as you can think of and then let the results tell
you which one is interesting. This is the process of science.

> Always a danger of
> rubbish-in  = rubbish-out,  so I am puzzled that Sheep writes
> that "fractional analysis will make such map based observation
> questions irrelevant".    Especially as he follows this with "One
> thing we do not understand clearly from traditional space syntax
> is when the visibility matrix (where I can see) and the
> permeability matrix ( where I can go ) differ. For example an
> office with half-height partitions, or an office with glass
> walls."       This is surely a critical point,  in particular
> because on first impressions it would seem that visibility maps
> reflect the experience of strangers, and permeability maps
> reflect the experience of  familiars  (residents?).

Perhaps. That is a hypothesis that you could test. Take a sample of people,
half strangers and half familar, and see whether the visibility map or the
permability map consistently correlated better or worse with one or the
other. I dont think anyone has done this precisely but Saif might have....

>
> The  fractional  analysis of the axial lines that make up a curve
> is most interesting   but why draw short, straight lines around a
> curve in the first place?  Is it because the curve restricts
> sightlines (as most streets do) AND because sightlines matter to
> the users in question?  If the users are local residents, perhaps
> it only matters that it is a continuous  walkable  path.  If the
> path curves through the lawns of the local park then sightlines
> are not restricted   there is no point at which strangers would
> loose sight of their destination.  The same goes for the
> underground walkway   do regular users find it confusing?  Don't
> they just KNOW which way to go?  Regular commuters find their way
> through a maze of tunnels in the London Underground stations
> without lifting their eyes from their newspapers!
>
> There is an important point towards the end of Sheep s mailing:
> "think about the effects of a stair case if you do take it do you
> always come out facing the direction you want? "    Orientation
> is a separate factor from wayfinding which I had not considered.
> I assume that the important point is that those who are familiar
> with a space know where they are when they get there, and do not
> need to maintain a sense of orientation.  However, when I first
> went to Venice I stayed for a week without a map.  I  knew  a
> number of  direct  routes across the city by gradually-extended
> exploration.  I recognized my departure points and my
> destinations.  Sometimes, to my surprise, I found that one
>  direct  route crossed another (or arrived at the same
> destination).  It was a surprise because my mental map had no
> global orientation:  I didn t know which destination was near
> another.  When I returned another year with a map I was
> fascinated by the relative location of landmarks, and just how
> convoluted some of my  direct  routes had been!
>
> The converse of this point is Alan s question: "the simplified
> 'visual' line correlates best - you have an interesting question
> to answer - 'why?"     Well surely this is because we are
> measuring "Routes along which people can keep their destination
> in sight."  Or as I put it before, 'continuous paths coincident
> with lines of sight.' (incidentally, Alasdair s  question of
> defining  exactly  the axial line surely refers to defining which
> lines are relevant to the  minimum-depth axial map , not to any
> old axial line, doesn't it?)   In Alan s next mailing,  he says
> "The procedure is both pragmatic and empirical, but axial maps
> are not arbitary. They reflect somthing about the world"  .
> Surely we can be more definite than this,  the axial line
> reflects what I just wrote, or perhaps something better
> formulated by those with long research experience,  but how can
> you work with it if you do not make it explicit?  You can t use
>  something  as a research tool can you?  This question is
> different from defining which lines are maximal.
>
> The following question, "Why should a map drawn one way correlate
> better with observed movement . . . "   seems to be another
> version of this same question:  if you know the mechanism, then
>  good maps  show all (and only) the features relevant to that
> mechanism, bad maps confuse the issue.   Alasdair writes that
> "there is nothing wrong with there being more than one solution,
> or indeed, calling several different solutions all "good" axial
> maps."     Again, can t we be a bit more definite about what
> types of axial map are possible? (leaving aside confused ones);
> permissible maps reflect the possible variations of mechanism.
>
> Surely there are only two types of mechanism available for human
> movement (at the whole body level):  Where am I able to go? and
> Where am I allowed to go?

Where can I see?, What do I understand (of where to go)? What do I remember
(of where I want to get to)? and lots more I suggest...
>
> The first one deals with the constraints of the physical
> environment and of our understanding of it (wayfinding, and
> possibly the  fluid  analysis of crowd movement  (by the way
> Alasdair, when did air cease to be a fluid?))  It seems to have
> two variable parameters,  prior knowledge and physical ability.
>  This might make four maps depending on what  watersheds  are
> found in the variables, or perhaps one map with variable figures
> annotated to each line.  Prior knowledge probably only has values
> of  stranger  ,  visitor  and  inhabitant .   Physical ability
> might perhaps be scaled as;
> Wheelchair   average   desperate. (to finish up with Alan s
> postulated pole-vaulting burglar).  It would need research to see
> where the variations along these parameters made a different to
> the features that need to be measured.  Has anyone done this?  Or
> am I wrong in this speculation of map-types?
>
> Of course, there is also the second question; Where am I allowed
> to go? For instance, when I walk through a carpark  and glance
> down an alley to see a courtyard beyond, why does it look like
> "the way to go" in some instances, but not in others?  I would
> suggest that it is not just whether I can see my destination
> (axial wayfinding) but whether it looks  private  (an issue of
> social control, not defensible space)

possibly some morphology issues in here like if the walls at the end are
angled it looks like it may lead some where but if orthoogonal it looks
closed.

>
> The two questions seemed to be equal partners in the first book
> (social logic of space) but since then spacesyntax seems to have
> split into  Hillier analysis  (axial lines, natural movement,
> co-presence) and  Hanson analysis  (boundary spaces, social
> control, observation).  I suspect that axial analysis works so
> well on city size problems because they 'average out' the
> variations in behaviour caused by personal differences.  At the
> opposite end of the scale, I was a little disappointed that
>  Decoding homes  concentrated so much on rooms (boundary spaces).
> This seems to do the opposite, to make personal relationships of
> occupants so definite that the universal effects of public
> movement seemed to become secondary.
>
> I feel that spacesyntax has unique ways to explain human
> behaviour in small systems of semi-public space (which is
> continuous and ambiguous), because it is here that purely spatial
> relationships are so important.   However, the mechanisms
> probably lie beyond the axial line:  perhaps someone has
> researched this already?  There are hints at the end of 'Decoding
> homes' that it is being given attention.  Is there a way of
> seeing what work is being done?  I appreciate the UCL website,
> where I have found papers by the main players, but there must be
> lots of other stuff going on isn't there?   Alan  writes that I
> "should read Ruth Conroy's PhD"  How do I do that?  Are there any
> summary papers published?  Then there was the comment about
> "theory or hypothesis like in my book", I don't think I know
> about this either.

Well, as soon as Ruth has had it examined it ends up on the shelves of the
University of London library. should have read: "theory or hypothesis-like,
in my book" where the 'book' is colloquial for 'according to me' :-)
>
> Once again, thank you for all the advice and information - on the
> website and on this list.  It has really been something to think about!
>
> Sincerely
>
> Tom Dine
> [log in to unmask]
>
> Chassay+Last Architects
> Primrose Hill
> London
>