# Digit Ratio — Digit Ratio (2D:4D)

> Tool for anonymous measurement of the second-to-fourth digit ratio for research. (iPhone/iPad app by Everyware Technologies S.L..)

- Source: https://appshunter.io/ios/app/digit-ratio/id1313005322 (this page in markdown: same URL + `.md`)
- Developer: [Everyware Technologies S.L.](https://appshunter.io/developer/718530491)
- Category: Business, Utilities
- Price: Free
- Rating: 1.50/5 from 2 App Store ratings · 1 written reviews indexed
- Age rating: 4+
- Requires: iOS 9.0 · 35 MB
- Languages: American English, European Spanish
- Released: 2017-11-29
- Data updated: 2026-06-03
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/digit-ratio/id1313005322/reviews.md

## What is Digit Ratio?

A now widely studied putative marker for prenatal sex hormones exposure or, more precisely, for the relative exposure to testosterone compared to estrogens while in uterus, is the second-to-fourth digit ratio (2D:4D), that is the ratio between the index (2D) and the ring (4D) fingers.

Digit-ratio app is a tool to obtain anonymous measurements of digit ratios (2D:4D).

Earlier studies that have stood the test of replication have reported that 2D:4D varies by sex and ethnicity but that male 2D:4D tends to be lower than female 2D:4D in all ethnic groups and the effect is strongest in the right hand. These differences emerge prenatally and appear to be stable during the developing years.

While a number of failed replications have been reported, 2D:4D appears to be successfully associated with cognitive abilities, impulsivity, aggression and risk-taking, among other effects on personality and cognition.

The objective of the research project is to collect anonymous measurements from multiple individuals. The measurements and profile data may be sent to a server for research purposes. No image will be sent.

## Key features

- Anonymous digit ratio measurement
- 2D:4D ratio calculation
- Prenatal hormone exposure marker
- Research data collection
- Personality and cognition studies

## Recent user reviews (1 of 1)

All indexed reviews: https://appshunter.io/ios/app/digit-ratio/id1313005322/reviews.md

### 2/5 — The Detection algorithm doesn’t work

*2018-12-02*

I’ve tried it in different light and on different surface but the palm detection algorithm doesn’t work. And in the few cases it detects the palm it can’t figure out the correct length of the fingers. All you would need to detect a palm is some basic adaptive thresholding so I’m confused why this performs so poorly.

## Frequently asked questions about Digit Ratio

### What is Digit Ratio?

Digit Ratio is an app that allows users to anonymously measure their second-to-fourth digit ratio (2D:4D). This ratio is a marker studied for its potential relation to prenatal sex hormone exposure.

### How does Digit Ratio collect data?

The app collects anonymous measurements of digit ratios and profile data, which may be sent to a server for research purposes. No images are sent.

### What is the 2D:4D ratio used for?

The 2D:4D ratio is studied for its potential associations with cognitive abilities, impulsivity, aggression, risk-taking, and other personality traits. It is believed to reflect relative prenatal exposure to testosterone versus estrogens.

### Is Digit Ratio free to use?

Yes, Digit Ratio is available for free. It does not have in-app purchases or advertisements.

### What devices does Digit Ratio support?

Digit Ratio is supported on iPhone and iPod devices.

### When was Digit Ratio last updated?

The latest version of Digit Ratio is 1.0.2, which was last updated on December 14, 2017.

### What is the age rating for Digit Ratio?

Digit Ratio has an age rating of 4+.

### What do users think of Digit Ratio?

Based on the available data, Digit Ratio has a rating of 1.5 stars from 2 ratings, suggesting a low user satisfaction.

## Version history (last 3 releases)

### 1.0.2 — 2017-12-14

This app has been updated by Apple to display the Apple Watch app icon.

Updated detection algorithm and CSV export format.

### 1.0.1 — 2017-12-10

Small improvements and changes in data export.

### 1.0 — 2017-11-29

No release notes.

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All apps by Everyware Technologies S.L.: https://appshunter.io/developer/718530491

## Related topics

[444 0 545](https://appshunter.io/ios/topics/444-0-545)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-06-03.*