--- title: RookLift | daily.dev description: A developer built a custom Garmin watch app to predict cognitive performance using chess ELO fluctuations as a proxy for mental clarity. Using logistic... canonical: https://daily.dev/posts/rooklift-wd4av0aef twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: RookLift | daily.dev og:description: A developer built a custom Garmin watch app to predict cognitive performance using chess ELO fluctuations as a proxy for mental clarity. Using logistic... og:url: https://daily.dev/posts/rooklift-wd4av0aef og:image: https://api.daily.dev/og/posts/wd4aV0AEF.png og:image:alt: RookLift og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # RookLift **[Hacker News](https://daily.dev/sources/hn)** · 5 min read · 0 upvotes · 0 comments ## Summary A developer built a custom Garmin watch app to predict cognitive performance using chess ELO fluctuations as a proxy for mental clarity. Using logistic regression on 1.5 years of sleep and exercise data, they achieved 60% prediction accuracy and discovered counterintuitive findings: REM sleep and moderate stress positively correlated with performance, while recent exercise and deep sleep showed negative or no correlation. The custom model often contradicts Garmin's built-in metrics, leading to behavioral changes like reducing alcohol for better REM sleep and scheduling cognitively demanding tasks based on daily predictions. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [What happened in 2007?](https://daily.dev/posts/what-happened-in-2007--tnttcgg9e) · Hacker News · 1 upvotes · 1 comments - [Sleep Tracking, Bluetooth Signals, and EMF: What Every Wearable User Should Know](https://daily.dev/posts/sleep-tracking-bluetooth-signals-and-emf-what-every-wearable-user-should-know-oau5bwhwl) · freeCodeCamp · 2 upvotes · 0 comments - [A burst of “pink noise” may lead to more restorative sleep](https://daily.dev/posts/a-burst-of-pink-noise-may-lead-to-more-restorative-sleep-houpauqx7) · MIT News · 0 upvotes · 0 comments --- Tags: [#machine-learning](https://daily.dev/tags/machine-learning), [#data-science](https://daily.dev/tags/data-science) [View this post on daily.dev](https://daily.dev/posts/rooklift-wd4av0aef) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"RookLift","url":"https://daily.dev/posts/rooklift-wd4av0aef","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/rooklift-wd4av0aef"},"datePublished":"2026-01-16T17:08:58.372Z","dateModified":"2026-01-16T17:09:17.297Z","description":"A developer built a custom Garmin watch app to predict cognitive performance using chess ELO fluctuations as a proxy for mental clarity. 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