State variables: Resources items are defined by a position, and a type which is characterized by quality Q r, and two parameters defining how difficult the resource type is to process (H r and S r), or ‘task difficulty’. H r defines the practice time (or experience) needed to develop half of the maximal skill for that resource type, and S r defines the shape of the function of how skill increases with experience (see ‘Skill learning’ below). Patches are emergent from clumps of resource items in space, and have a type defined by a set of 5 resource types that only occur in patches of that type. Foragers are defined by a position and heading, a current action and a time to its completion, short-term memory about movement and foraging goals, and long-term memory about the rewards associated with resources and resource processing skill. Foragers can differ in their information about resources and skill levels, as well as in their propensity for learning as defined by parameters that can mutate (see Table 1).