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Monday, August 9th, 2010

tante suhrkamp lässt erzählen

“Aus der Sicht des Gehirns”, Gerhard Roth, suhrkamp taschenbuch wissenschaft, S. 40ff.:

So haben wir bis zu einer Distanz von ca. 6 Metern ein direktes räumliches (stereoskopisches) Sehen, also eine echte Dreidimensionalität. […] Die stereoskopische Tiefenwahrnehmung ist sehr präzise, und deshalb können wir mit ruhiger Hand fast auf den Millimeter genau nach nahe gelegenen Gegenständen greifen. Das hochpräzise räumliche Sehen ist aber auf den Nahraum beschränkt, was natürlich Sinn macht. Mit zunehmender Entfernung wird die Disparität der beiden retinalen Bilder immer kleiner, und ganz andere Hilfsmittel zur Entfernungsschätzung kommen zum Einsatz, die auch mit einem Auge funktionieren. […] Eines dieser Hilfsmittel heisst Bewegungsparallaxe und nutzt die Tatsache aus, dass bei seitlichen Kopfbewegungen nahe Gegenstände sich stärker bewegen als etwas entferntere, und sich jene vor diesen hin und her zu bewegen scheinen.

Sehen wir mal davon ab, dass hier ein Wissenschaftler Stammeldeutsch schreibt – “was natürlich Sinn macht”, Lektor hin, Kommunikationswille her – dann bleiben immer noch die faktischen Gurken in diesem Kopfsalat: Disparitätswinkel nehmen mit der Entfernung ab, soweit schon richtig, aber das bedeutet nur, dass in grösserer Entfernung grössere Abstandsunterschiede nötig sind, um denselben qualitativen Tiefeneindruck zu gewinnen. Wer schon mal im Wald gestanden hat, weiss, dass binokulares Tiefensehen durchaus nicht auf die nächstgelegenen sechs Meter beschränkt ist; es sei denn, er war vor lauter Bäumen zu abgelenkt, genauer hinzugucken.

Die von Roth zur Behebung des von ihm erfundenen 3D-Notstands dann ins Feld geführte Bewegungsparallaxe ist drolligerweise geometrisch mit Disparitäten vollständig identisch: Ob ich mein Auge sechs Zentimeter seitwärts verschiebe oder mir stattdessen dort einfach ein zweites wachsen lasse, perspektivisch ist das ein und dasselbe.

Und “echte Dreidimensionalität”: auch Quatsch. Selbst mit fünf Augen sähe man nicht hinter die Dinge, und wäre also noch immer von einer einzelnen visuellen Oberfläche unterschiedlichen Abstands umgeben. Und in den Ausnahmefällen, in denen man zwei Dinge hintereinander sehen könnte, im Fall schmaler Objekte etwa, oder bei transparenten Folien, sorgt die Disparitätsgradientenschwelle meist dafür, dass nicht beide gleichzeitig voll sichtbar sein können. Halten Sie doch mal zwei Finger hintereinander, einen nahe, einen weiter weg. Ist der Abstandsunterschied gross genug, sieht zwar jedes Auge beide Finger, aber binokular oder “echt dreidimensional” sieht man nur den, den man direkt ansieht. Der andere Finger wird doppelt gesehen, sein Abstand ist unsicher. David Marr nannte das visuelle Ergebnis deshalb den “two-and-a-half-D sketch”. Zweieinhalb-D, Herr Roth, “echt”.

Ich freu mich schon aufs vollständig überarbeitete Kapitel zum freien Willen. Das wird bestimmt toll.

Thursday, July 15th, 2010

What is that shit?

Hard to say what the source of the particular power of Rebney’s rant is. Somehow, the mixture of frustrated anger and self deprecation, contrasting with the mindless task of praising a Winnebago – itself the perfect image of a thwarted desire to escape, of resistance domesticated – rises above the heat, the flies and the adversities of the daily grind, and manages to inspire.

Rebney’s story, which the documentary Winnebago Man set out to find and tell, is one of media transition, first from the austere news machine of the middle of the 20th century into the entertainment complex of its end, then on into the fragmented world of me-media. Rebney, a veteran of CBS, does Winnebago spots to escape the Stahlbad of entertainment, and then finds himself being the viral harbinger of the next wave, before the term viral has even been coined. He finally understands that he is not used as a distraction, when he first faces his audience in San Francisco, in a sequence that is both tense and moving.

The movie’s premiere last Friday was supported by the presence of Michael Moore and Jeff Garlin, who threw the audience a bone by claiming that Curb Your Enthusiasm’s very concept was inspired by Rebney’s outbreaks. But the biggest thrill was seeing the man himself, pushing 80, kneeling down in the hope for a publishing deal, increasing the punishment on Bush Jr. from a hot poker up his ass to “being hanged like Goering”, flirting with the ladies, and just being a complete fucking delight.

A little earlier, during the movie, my mood was dampened a little, when Rebney and Steinbauer walk into Golden Gate park, and a sudden wave of melancholy sadness washed over me: I used to live there. I don’t any more. In fact, most of the things I love are in the past and far away. I’m old. Boo hoo. But then that made me angry, and I gave myself a clue from Jack’s book: I don’t want any more sentimental bullshit anytime during this post, from anyone, and that includes me.

There. Now go, see the movie.

Wednesday, June 23rd, 2010

Shermer’s Folly

Figure 6: Some nonsense (not to scale)This plot is from chapter 4 of Michael Shermer’s book “Why People Believe Weird Things”, and it’s quite amusing.

The section of the book this is from concerns ESP experiments. Participants in these experiments have to predict one of five symbols on an unseen card, and the plot is meant to show the chance of a participant getting x of the answers right when being asked 25 times. Predictably, getting 5 right out of 25 is the most likely, but higher numbers of hits are entirely expected, and their occurence alone does not mean much. Shermer stops with the negative statement – high performance doesn’t mean ESP – and doesn’t spell out what a correct analysis would look like – not looking at a single result, but comparing a distribution of results to that predicted from chance – but this unfortunate focus on gleeful debunking rather than the education of the reader isn’t my concern. It’s the plot itself. Look at it.

Its x axis runs from -2.5 to 12.5. Bars of unit width indicate the probabilities of getting a certain number of answers right, and a Gaussian curve (Shermer calls it a Bell curve in the legend, and a normal distribution in the chapter text) to fit the bar data. Pretty much all of this is awful. First of all, fractions of x make no sense. The number of correct answers can only be a whole number, therefore probabilities should be plotted for whole numbers alone. If you want to use bars, make them discontinuous to emphasize their discrete character. Additionally, both the Gaussian and the leftmost bar extend into negative values, which also do not make sense for x. Negative values shouldn’t be on this plot at all. All this could be simply due to sloppy graphical design, of course, but the Gaussian extending into the negative is in fact a hint of the biggest error here: this distribution is not a normal distribution at all. To show a Gaussian here is a blatant statistical and conceptual error.

Random answering in a task like this in fact follows a binomial distribution. Interestingly, the numbers on the bars are from the correct binomial (except for 0.0238, which should have read 0.0236), meaning that whoever prepared the data knew what they were doing. But Shermer, fitting a Bell curve to them, clearly does not. You can even see it’s a bad fit. The bars don’t look symmetrical at all. Furthermore, the claim in the legend that “in a group of 25 several scores [above 7] will always occur purely by chance” is also quite false. He himself provides the probability for scoring below 8, which is 89.1%. Thus, in a group of 25, the chance of everybody scoring below 8 is 89.9% to the 25th power, or 5.56%. In other words, roughly one in eighteen such groups will have nobody scoring 8 or higher. There are lies, damn lies, and statistics done by fools.

Claims of the paranormal are emotionally and spiritually appealing, and it is important to counter them both on their own grounds by providing equally appealing stories about the world, and also by clearly showing where their purported proofs are untenable. Michael Shermer is the founder of the Skeptics Society, who claims this as their task, and he adopts a smug tone of intellectual superiority over the misled and uneducated foolish masses throughout this book. Yet apparently he doesn’t know what he’s talking about himself. He even told me so at the end of his foreword: “why should [you] believe anything [I] say? […] You shouldn’t.”

In the end, the whole thing is probably just a clever lesson in scepticisim. Or is it?

Thursday, April 29th, 2010

MADDness

Reasons to keep the drinking age at 21: Since the drinking age in New Jersey was raised to 21, the number of young people killed in drunk driving crashes has dropped nearly 78%. Need we say more…

I’ve stared at this claim numerous times, while being carried hither and tither by PATH. In it, MADD, the non-profit that took its name from Alhazred’s infamous Acronomicon (A Complete Reference Of Nerdy Or Maximally Impossibly Convoluted Organization Names) is trying to rally support for their cause, and they’re doing it in a way that makes my number sense go off. To the Mathcave!

First: they don’t tell us what they base their numbers, excuse me, what they base their number on. 78% of what, taken from which source, and calculated how? I realize it’s just a small subway ad, but it does manage to mimic a statistical claim quite well. Which it frankly isn’t. It’s an unfounded and barely even meaningful assertion.

Second, they don’t mention when exactly this raising of the drinking age happened, do they? It happened way back in 1982. In the 28 years since, the number of fatal accidents overall might have dropped considerably. Given the safety advances since then, it’s a fair bet it has. If it had dropped by as much as 80%, the number MADD gives us for drunksters would be merely the average drop. The same were true if just the number of young people on the road, or the number of young involved in any kind of crash, had dropped by 80%. In fact, there is a whole host of variables that a claim like this one needs to be controlled against for it to have meaning.

Third, the drop is in “young people killed in drunk driving crashes”. Sounds like that also includes crashes caused by drunk adults. Which are irrelevant to the question of drinking age.

And fourth, how many saved lives do those 78% actually correspond to, and what fraction are they of the total number of young people killed in traffic accidents? If both were small numbers, would the good of the few really outweigh the good of the many here? While this argument assumes there is a net benefit from getting drunk, which itself may seem debatable, there is no foregone conclusion either way. Not allowing people under 21 to drive at all would make their fatalities drop even further, yet I don’t envision that implemented any time soon. The cost would be too high.

Just to be clear: I think drunk driving is irresponsible and stupid at any age, and young people, especially males, are much more likely than the average to do it. They can’t help it, their frontal lobes are hormonal mush. But whether or not raising the drinking age lowers the risk is an empirical question that deserves proper treatment. Mothers, do not mislead us! It makes us SADD (Scientists Against Data Distortion).

Thursday, April 22nd, 2010

Und was führt Sie her?

  • zucken tote Fische Kochsalz
  • brompton stupid
  • wie heißt das auf deutsch; Take it hau i t on the kopp of a to give of
  • fische sind feige
  • sex with animals
  • riesiger steinklumpen
  • rausgeschnittene zunge
  • kaputte typen homepage
  • stilles trinkwasser bunte getränkeflasche
  • kummer dose diktat
  • The Perfect Ass – Riesen-Po black
  • Feeling Like a Fraud german
  • fische selbstzerstörerisch
  • würmer in der küche
  • defenition of the word ¨untenrum¨
  • translate der hund ist ja sweet


Tuesday, September 8th, 2009

ciphers

I hate to bitch. Okay, that’s a lie, I love to bitch, sorry. But at least I can spare you my prefacing this newest bitchfest with the qualifier that the book I’m bitching about is great otherwise. We’ve been over that already, it’s scorched earth. There, spared you. Considerate me.

What is going on with the Wallacester and the math? I’m now about halfway through Infinite Jest (what’s half of infinity? Am I done, then?), and as of yet there is nought in terms of indication that his shortcomings in the land of numbers are a jester’s crown worn for some – however obscure – purpose of Jest, finite or otherwise.

The newest item from DFW’s confoundry: Eschaton’s rules are only touched upon tangentially in the main novel’s text, vague hints at complexities of being hit, influenced by weather and all sorts of other variables, which is fine. But then we are taken into lengthy details in an endnote about how the First Mean Value Theorem of Integration allows Lord to get by without calculating complicated integrals for setting up the game. In some rather unspecified way the initial allocation of resources to players for a game’s new round depends on the average value of some equally underspecified ratio, and so Lord needs to calculate the integrals of this variable over previous game time. Except that apparently he doesn’t, because this magical Theorem allows him to use a shortcut right out of the convolved space of higher math into a paradise of simplicity. Which sounds quite nice. And is quite untrue.

The average value of a variable over an interval of time will be it’s integral over said interval divided by the interval’s length. Now, the First Mean Value Theorem indeed guarantees that the integral comes to the same as the intervals length multiplied with the value of the function at a point within the interval, and so that the average itself is identical to the value of the function at this point within the interval. The logic of this is nicely developed in the lengthy endnote’s lively interchange between Incandenza and Pemulis. But nohow does this integral theorem allow you to infer which point within said interval you’d have to choose, and thus for all practical purposes of setting up tennis socks and buckets of bald nuclear balls, this little piece of abstract mathematical wisdom, rather than being the prized insight allowing young kids to cheat the forces of nature Pemulis wants to sell it to us as, is utterly useless. Plus also, in the sloppy plot nicely labeled Halsadick, the supposed average value doesn’t even look like the actual average value, for crying out loudly in complicated semantic structures.

A bit later we read that computer discs squeeze whole high definition movies into 4.8 MB of binary space, which claimed figure must have been ludicrously and unrealistically low in the B.S. 90s already. Such a disc wouldn’t hold two single uncompressed HD images of finely rendered water (assuming 24 bits of liquid color shades). A typo, one hopes. The DVD was introduced in 1995, by the way.

They still are a puzzle, these oddly shaped holes in the otherwise beautiful fabric of this tome, and I’ll keep on logging them. It amuses me.

Thursday, February 19th, 2009

how not to estimate time



1
typedef double (*TDLLEstimateTime)(int,int,int,int,int);

2
TDLLEstimateTime DLLEstimateTime;

3
DLLEstimateTime = (TDLLEstimateTime)GetProcAddress(PsiDLLHI, “EstimateTime”);

4
double EstimateTime(int rep, int n1, int n2, int n3, int n4) {
if (SetupDLL()==1) return DLLEstimateTime(rep,n1,n2,n3,n4);
return 0;
};

Tuesday, February 10th, 2009

Designated

Mit einem Anflug von Schuldgefühl fotografiere ich ins Foyer der architektonischen Sonderheit mit der gewürfelten Fassade, ein Tischfussballtisch vor dem Portierstisch. Hinter mir rollt ein Kleinwagen die verlassene Strasse am MIT Campusrand entlang, und er rollt zu langsam. Ich erwarte Security, Zurufe, Bildlöschgebote, Rüpeleien. Stattdessen rollt das Auto an mir vorbei, driftet an den Strassenrand und schrammt dann hörbar am aufgeworfenen Schnee entlang. Es biegt vor mir auf einen Parkplatz ein, reflexhaft erwarte ich, nun doch noch angesprochen zu werden, aber als ich das Gebäudeeck erreiche fallen beide Türen ins Schloss, Rückwärtsgang, Abfahrt. Mein Lachen hängt kurz als Nebelwolke in der Luft und verfliegt.



leghand = [leghand; newline];

vox.confusion = zeros(length(vox.nvox),vox.ncond,vox.ncond);

vox.dist.l1(n) = fminbnd(@(a) abs(interp1(tmpbins, vox.dist.cum{n},a)-.95), min(tmpbins),max(tmpbins));

% leave motion in
set(handles.RegMot,'Value',0); drawnow;
DoAnalyze_Callback(handles.DoAnalyze, eventdata, handles);

wgt = cat(3, mwgt, dwgt, wgt-handles.vox.wgt, wgt, handles.vox.wgt, mw_m, handles.vox.mw(:,:,1,:));

Thursday, February 21st, 2008

A Telephone Call (2008 edition)


   function onIdle;

   global selfesteem address

   at_wits_end = -1; deluded = 0; elated = 1;
   state = deluded;
   while state == deluded;
     pause(rand(1)*600);
     state = at_wits_end;
     for i = 0:5:500,
       disp(num2str(i));
       m = getmessages;
       if ~isempty(find(m.sender==address)),
         state = elated;
         break;
       end;
       qualms = rand(1);
       if qualms < i/1000,
         state = deluded;
         break;
       end;
     end;
   end;

   sendmail(address,';)');

   selfesteem = selfesteem + state;