Certain models of spoken-language processing, like those for many other perceptual and cognitive processes, posit continuous uptake of sensory input and dynamic competition between simultaneously active representations. Here, we provide compelling evidence for this continuity assumption by using a continuous response, hand movements, to track the temporal dynamics of lexical activations during real-time spoken-word recognition in a visual context. By recording the streaming x, y coordinates of continuous goal-directed hand movement in a spoken-language task, online accrual of acoustic-phonetic input and competition between partially active lexical representations are revealed in the shape of the movement trajectories. This hand-movement paradigm allows one to project the internal processing of spoken-word recognition onto a two-dimensional layout of continuous motor output, providing a concrete visualization of the attractor dynamics involved in language processing. dynamical systems ͉ psycholinguistics ͉ word recognition

Fitts's law is one of the most well-established principles in psychology. It captures the relation between speed and accuracy in performed and imagined movements. The aim of this study was to determine whether this law also holds during the perception of other people's actions. Subjects were shown apparent motion displays of a person moving his arm between two identical targets. Target width, the separation between targets, and movement speed were varied. Subjects reported whether the person could move at the perceived speed without missing the targets. The movement times reported as being just possible were exactly those predicted by Fitts's law (r(2)= .96). A subsequent experiment demonstrated the same lawful relation for the perception of a robot arm (r(2)= .93). To our knowledge, this makes Fitts's law the first motor principle that holds in imagery and the perception of biological and non-biological agents.

Asymmetries in posterior ERP components, such as the N1, are generally taken to reflect the visual processing of spatial information in absolute (fixation-based) coordinates. Yet, it is also well established that the position of an object can be coded relative to the position of other objects. To examine the ERP correlates of relative spatial coding, two experiments were conducted in which spatially neutral target stimuli were preceded, accompanied, or followed by laterally presented, task-irrelevant accessory stimuli. Targets presented simultaneously with a lateral accessory evoked, despite physical asymmetry, a bilateral, symmetric N1. Targets that followed the accessory evoked, despite physical symmetry, an asymmetric N1, with a maximum contralateral to the accessory N1. Thus, lateralizations in the N1 range already reflect relative spatial coding rather than just the processing of the absolute location of incoming information.

Because reaction time (RT) tasks are generally repetitive and temporally regular, participants may use timing strategies that affect response speed and accuracy. This hypothesis was tested in 3 serial choice RT experiments in which participants were presented with stimuli that sometimes arrived earlier or later than normal. RTs increased and errors decreased when stimuli came earlier than normal, and RTs decreased and errors increased when stimuli came later than normal. The results were consistent with an elaboration of R. Ratcliff's diffusion model (R. Ratcliff, 1978; R. Ratcliff & J. N. Rouder, 1998; R. Ratcliff, T. Van Zandt, & G. McKoon, 1999), supplemented by a hypothesis developed by D. Laming (1979a, 1979b), according to which participants initiate stimulus sampling before the onset of the stimulus at a time governed by an internal timekeeper. The success of this model suggests that timing is used in the service of decision making.