Intuitively, we are aware of our own thoughts in a way that is quite different to the way that we are aware of other people's thoughts; each of us is privileged in knowing only our own thoughts directly, whereas we have to *infer* others' thoughts on the basis of their overt behaviour. The ability to monitor one's own thoughts is termed "metacognition", whereas the ability to monitor others' thoughts is termed "mindreading". The intuitive view of metacognition described above has led some (so-called "two systems" theorists) to claim that distinct psychological mechanisms underpin metacognition and mindreading, and that metacognition is evolutionarily and developmentally prior to mindreading. This claim is disputed by another group of ("one-system") theorists who argue that mindreading and metacognition actually rely on exactly the same core psychological mechanism (despite common intuition), and that metacognition actually emerged as a by-product of the evolutionary need to mind-read others. Two-systems theorists use two potentially powerful arguments to support their view. First, they argue that non-human primates are capable of performing well on tests of metacognition even though such primates show little evidence of mindreading ability. Second, they argue that humans with autism spectrum disorder (ASD) show intact metacognitive ability despite impaired mindreading. If these arguments are validated, then this would rule out the one-system view of the relation between mindreading and metacognition. However, one-system theorists have challenged these arguments, claiming that (a) the supposedly metacognitive tasks that non-human primates perform well on do not, in fact, require metacognitive awareness, and (b) people with ASD *do* show metacognitive impairments. There is, however, very little empirical research to decide between these arguments and counter-arguments. Therefore, the aim of our proposed research is to test these theories in a systematic fashion by employing multiple kinds of metacognitive task across two sets of experiments.In the first set of experiments, we will manipulate the demands of metacognitive tasks in systematic ways to establish whether the kinds of task used to test metacognition in non-human primates really do require awareness of one's own thoughts. Neurotypical adults will take part in this set of studies.In the second set of experiments, we will assess metacognitive monitoring among adults with ASD and neurotypical adults who are closely similar to participants with ASD in terms of age and general intelligence. We will use a variety of tasks, including those kinds that are used to test metacognition in non-human primates. Together, these experiments will allow us to decide between the competing theories of the relation between metacognition and mindreading. In addition to supporting theory development, our proposed research will be important in understanding the nature of cognitive functioning in people with ASD. It is striking how little research there is into metacognition in ASD, given that many hundreds of studies that have explored mindreading in this disorder. Indeed, difficulties with such *self*-awareness might explain aspects of the behavioural features of ASD that difficulties with mindreading do not so easily explain (e.g., behavioural inflexibility). Thus, we hope that our proposed research will, in the end, have practical benefits for people with ASD, by informing teaching practices and intervention efforts designed to enhance learning and cognitive-behavioural functioning among people with this disorder.