A developmental shift in processes underlying successful belief-desire reasoning

Young children's failures in reasoning about beliefs and desires, and especially about false beliefs, have been much studied. However, there are few accounts of successful belief-desire reasoning in older children or adults. An exception to this is a model in which belief attribution is treated as a process wherein an inhibitory system selects the most likely content for the belief to be attributed from amongst several competing contents [Leslie, A. M., & Polizzi, P. (1998). Developmental Science, 1, 247-254]. We tested this model with an ‘avoidance false belief task’ in which subjects predict the behavior of a character, who wants to avoid an object but who is mistaken about which of three locations it is in. The task has two equally correct answers—in seeking to avoid the location where she mistakenly believes the object to be, the character might equally go to the location where the object actually is, or to the remaining empty location. However, the model predicts that subjects will prefer one of these answers, selecting the object's actual location over the empty location. This bias was confirmed in a series of five experiments with children aged between 4 and 8 years of age. A sixth experiment ruled out two rival explanations for children's biased responding. Two further experiments found the opposite bias in adults. These findings support one selection model as an account of belief-desire reasoning in children, and suggest that a different model is needed for adults. The process of selecting contents for mental state attributions shows a developmental shift between 8 years of age and adulthood.     

Why ‘Nonexistent People’ Do Not Have Zero Wellbeing but No Wellbeing at All

Some believe that the harm or benefit of existence is assessed by comparing a person's actual state of wellbeing with the level of wellbeing they would have had had they never existed. This approach relies on ascribing a state or level of wellbeing to ‘nonexistent people’, which seems a peculiar practice: how can we attribute wellbeing to a ‘nonexistent person'? To explain away this oddity, some have argued that because no properties of wellbeing can be attributed to ‘nonexistent people’ such people may be ascribed a neutral or zero level of wellbeing, setting the baseline for comparatively assessing the harm or benefit of coming into existence. However, this line of argumentation conflates the category of having zero wellbeing with the category of having no wellbeing. No Φ, unlike a zero level of Φ, is not comparable to levels of Φ — neutral, positive, or negative. Considering the nature of wellbeing and the fact that ‘nonexistent people’ cannot (metaphysically or conceptually) have wellbeing determinative properties, it follows that ‘nonexistent people’ have no wellbeing rather than zero wellbeing.