Quick puzzle about utility functions under affine transformations
Here's a puzzle based on something I used to be confused about:
It is known that utility functions are equivalent (i.e. produce the same preferences over actions) up to a positive affine transformation: u'(x) = au(x) + b where a is positive.
Suppose I have u(vanilla) = 3, u(chocolate) = 8. I prefer an action that yields a 50% chance of chocolate over an action that yields a 100% chance of vanilla, because 0.5(8) > 1.0(3).
Under the positive affine transformation a = 1, b = 4; we get that u'(vanilla) = 7 and u'(chocolate) = 12. Therefore I now prefer the action that yields a 100% chance of vanilla, because 1.0(7) > 0.5(12).
How to resolve the contradiction?
You Are A Brain - Intro to LW/Rationality Concepts [Video & Slides]
Here's a 32-minute presentation I made to provide an introduction to some of the core LessWrong concepts for a general audience:
You Are a Brain [Google Slides] - public domain
I already posted this here in 2009 and some commenters asked for a video, so I immediately recorded one six years later. This time the audience isn't teens from my former youth group, it's employees who work at my software company where we have a seminar series on Thursday afternoons.
Wisdom for Smart Teens - my talk at SPARC 2014
I recently had the privilege of a 1-hour speaking slot at SPARC, a yearly two-week camp for top high school math students.
Here's the video: Wisdom for Smart Teens
Instead of picking a single topic, I indulged in a bunch of mini-topics that I feel passionate about:
- Original Sight
- "Emperor has no clothes" moments
- Epistemology is cool
- Think quantitatively
- Be specific / use examples
- Organizations are inefficient
- How I use Bayesianism
- Be empathizable
- Communication
- Simplify
- Startups
- What you want
A proposed inefficiency in the Bitcoin markets
[Beliefs about order of magnitude of Bitcoin's future value] --> [Beliefs about Bitcoin's future price] --> [Trading decisions]
Atkins Diet - How Should I Update?
This seems like an authoritative 25-year research project that the Atkins diet is pretty bad:
http://www.nutritionj.com/content/11/1/40/abstract
Right now my belief is that the Atkins diet is good. It's backed by anecdotal evidence of trying a low-carb diet for 18 months following a 12-month low-fat diet and seemingly getting better results with the low-carb diet.
I'm counting on LWers to tell me how to update my belief in light of this study. Thanks.
Quixey Challenge - Fix a bug in 1 minute, win $100. Refer a winner, win $50.
Hiring is so hard that we spent a man-month creating a sub-startup to do it. The product is the Quixey Challenge which is running today until 7pm PST (GMT-8).
Benefits of playing:
- You can learn something from our craftsmanship of the algorithms (we work hard on them)
- The 1-minute challenge is a rush
- You can make money
- If you do well you can interview at Quixey
Quixey is hiring a writer

We've posted about jobs at Quixey before:
Quixey - startup applying LW-style rationality - hiring engineers
Since then we've hired LessWrong user cata. And it occurred to us that the LessWrong community is not only full of software engineers, it's also full of unusually strong writers.
Quixey - startup applying LW-style rationality - hiring engineers
Quixey is a 2-year-old startup with a lot of ties to the rationalist community. Our product is an all-platform "functional search" engine for apps. Our main engineering task is to build the most accurate possible map of all software on all platforms (the "functional web"), and write search algorithms that let users find apps to do what they need.
We're hiring top-notch engineers for full time positions in our Palo Alto, CA office. If your overall engineering skill level is "Google+", we have a lot to offer:
Quixey Engineering Screening Questions
My startup, Quixey, is looking to hire a couple top-notch software engineers. Quixey is an early-stage stealth startup founded in October 2009. We are launching our beta product this month: An all-platform app directory and "functional search" engine that lets users query for software by answering the question: What do you want to do?
We are confident that Quixey's functional search will be qualitatively better than all existing solutions for finding web apps, mobile phone apps, desktop apps, browser extensions, etc. Our prototype returns significantly more relevant search results in head-to-head comparisons with all the iPhone and Android app search solutions that currently exist(!)
Our office is on University Ave in Palo Alto. If you live in the Bay Area and want to join a hot tech startup extremely early (employee #1, high-equity compensation package), and you're better than the average Google engineer, then please try our screening questions. If you're the kind of person we're looking for, the questions shouldn't take you more than a few minutes each.
Questions
1. Write a Python function findInSorted(arr, x). It’s supposed to return the smallest index of a value x in an array arr which, as a precondition, must be sorted from least to greatest. Or, if arr doesn’t contain an element equal to x, the function returns -1. Make the code as beautiful as possible (without sacrificing asymptotically optimal performance characteristics).
2. Write a JavaScript function countTo(n) that counts from 1 to n and pops up an alert for each number (i.e. alert(1), alert(2), ..., alert(n)). Easy, right? Except you're not allowed to use while- or for-loops. (And you're not allowed to trick the interpreter using "eval", or dynamically generated <script> elements appended to the DOM tree, or anything like that.)
For problem 2, the time and space requirements of your function should be as good as those of the asymptotically optimal algorithm, even without tail call optimization.
Email your answers to liron@quixey.com and I'll get back to you right away. Please don't post your answers in this thread because that will make my filter really noisy. If you do well on the screening questions, we will want to bring you in for an interview.
Bloggingheads: Robert Wright and Eliezer Yudkowsky
Sweet, there's another Bloggingheads episode with Eliezer.
Bloggingheads: Robert Wright and Eliezer Yudkowsky: Science Saturday: Purposes and Futures
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