Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2017 May 9;21(1):99–131. doi: 10.1007/s10683-017-9527-2

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

© The Author(s) 2017

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

PMC Copyright notice

Fig. 2 — Contributions over time. Numbers in parentheses are the mean contributions in each experimental condition. Error bars indicate 95% confidence intervals (clustered at the group level)