Skill learning: A forager i’s skill s ir for processing a specific resource r is a function of experience t ir and ‘task difficulty’: 4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$ s_{ir} = \frac{t_{ir}^{S_{r}}}{H_{r}^{S_{r}} + t_{ir}^{S_{r}}} $$ \end{document}sir=tirSrHrSr+tirSr