 To understand the purposes of the HBE project, let’s consider one of its classic examples: Kaplan and Hill’s (1992) work on prey choice strategies amongst the Ache foragers of Paraguay. Just as in non-human behavioral ecology, behavioral strategies in HBE are usually described as complex behavioral dispositions. Behavioral dispositions involve behavioral responses to local stimuli; behavioral strategies then involve producing a set of different responses to a set of different stimuli (i.e. the response conditions of the strategy). According to Kaplan and Hill, the Ache prey choice strategy involves choosing a variety of different potential prey items from the environment; whether or not a prey item is taken depends on a number of circumstances acting as the response conditions: for example, the presence of prey with certain specific features, such as the caloric return of the prey given the time necessary to process it (known as the profitability); the rate at which that prey occurs in the environment; whether or not the prey is encountered on their search; and the search time available on a foraging trip. HBEs usually describe behavioral strategies in terms of an “epigenetic” or decision rule, which is usually given as a mathematical function mapping values for the response conditions in the environment onto the appropriate values for the parameters of the behavioral output. Kaplan and Hill’s work also provides such an epigenetic rule (see Kaplan and Hill, 1992, 170), which describes the relationships between search time, profitability and so on, to decide which prey will be taken on encounter when the Ache are out foraging. Kaplan and Hill’s observations suggest that, on the whole, the Ache are using a strategy which is close to the maximally adaptive strategy suggested by their prey choice model. The question, then, is how to interpret Kaplan and Hill’s method; what is the purpose of showing that the Ache have a strategy of this kind?