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The prevalence of a parent-reported diagnosis of autism spectrum disorder before age 7 in Australia was higher in the B cohort. Data from future Longitudinal Study of Australian Children waves will clarify whether autism spectrum disorder has been diagnosed earlier in the B cohort or if there is a continued increase in prevalence. Future waves will also provide crucial information about the types and severity of problems experienced during the primary and secondary school years which will assist service planning.

THE ROlE Of ExECuTIVE fuNCTION, specifically inhibitory control and generativity, in symbolic play was investigated in 20 children aged 48-89 months. Assessment of inhibitory control was via the Sun-Moon Stroop task, and generativity was assessed with the Semantic Fluency task, as well as a new object substitution task which required children to generate as many uses of toys as possible. Symbolic play ability was assessed under both structured conditions, using the Test of Pretend Play (Lewis & Boucher, 1997), and during free play. The results indicated that the ability to inhibit prepotent responses was associated with children's symbolic play skills, even after controlling for mental age. In contrast, generativity scores on both tasks were not correlated with symbolic play, indicating that only some aspects of executive function are implicated in symbolic play. The validity of the tasks used to measure executive function is discussed.

Factors associated with spatial reference in a small-scale space were investigated in three experiments. Subjects were first trained to anticipate an event at one specific location from two different directions of facing. They were then required to locate this event from a novel direction. Both 6-and 8-month infants visually anticipated the whereabouts of the event from the novel direction and displayed persistent visual fixation towards the place where it had previously appeared. For 8-month infants, successful anticipation was dependent neither on the distinctiveness of landmarks at the event position nor on the angle of their change in direction of facing. It was concluded that, at least for the space in front of the body, young infants are not exclusively limited to a fixed egocentric reference system for determining object or event location.Ability to perceive the fixed location of an object or an event in space despite observer movement, i.e. 'position constancy', is an important feature of cognitive development thought to be exhibited late in the first or early in the second year of life. The conditions which govern this ability have not been extensively studied. The general aim of the experiments reported here was to investigate these conditions using anticipatory looking and duration of fixation as indices.In considering position constancy, three typical situations involving change in the position of an observer relative to a stable surround can be identified. In the first, subjects are rotated while remaining in the same place; in the second they are relocated while facing in the same direction and in the third, they are both rotated and relocated. In all cases the position of objects and events relative to the subject undergoes change. In the interest of clarity, the effect of rotation will be referred to here as change in the direction of facing and relocation as change in the position of observation.

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