Stimulus timing by people with Parkinson's disease

Previous literature suggests that Parkinson’s disease is marked by deficits in timed behaviour. However, the majority of studies of central timing mechanisms in patients with Parkinson’s disease have used timing tasks with a motor component. Since the motor abnormalities are a defining feature of the condition, the status of timing in Parkinson’s disease remains uncertain. Data are reported from patients with mild to moderate Parkinson’s disease (both on and off medication) and age- and IQ-matched controls on a range of stimulus timing tasks without counting. Tasks used were temporal generalization, bisection, threshold determination, verbal estimation, and a memory for duration task. Performance of patients was generally “normal” on all tasks, but significant differences from performance of controls were found on the memory for duration task. Among the “normal” effects noted were arithmetic mean bisection, asymmetric temporal generalization gradients, and subjective shortening on the memory for duration task. The results suggest (a) that some previous reports of timing “deficits” in Parkinson’s patients were possibly due to the use of tasks requiring a timed manual response and (b) small differences between patients and controls may be found on tasks where two stimuli are presented on each trial, whether patients are on medication or off it.     

Typicality and Graded Membership in Dimensional Adjectives

This paper concerns an investigation of the manner in which typicality constrains graded membership in antonymous dimensional adjectives such as short/tall and cheap/expensive using the conceptual spaces framework. In this framework, items are organized in a space comprised of one or more dimensions along which they can be compared. The items’ graded membership is established by their relative proximity in this space to the prototypical instances of contrasting concepts. Because dimensional adjectives can be applied to an indefinite variety of things and grammatically have no upper bound to serve as cognitive reference point, they have been argued to lack prototypes. We present the results of an empirical study showing that the conceptual spaces framework can nevertheless be extended successfully to dimensional adjectives by complementing them with a comparison class argument (such as short/tall for an adult man and cheap/expensive for a smartphone), allowing participants to retrieve meaningful prototypical instances, which can be used to establish membership degree. Since dimensional adjectives are subjective, we investigate how the framework can accommodate interindividual variability in membership degree judgments. We find that the predictions of the framework significantly improve if prototypical instances themselves are assumed to come with a gradient instead of being considered equally typical, thereby providing a more fine‐grained account of typicality and furthering the development of the conceptual spaces framework.