Thematic Roles in Language Processing

We present some ideas about how thematic roles (case roles) associated with verbs are used during on-line language comprehension along with some supporting experimental evidence. The basic idea, following Cottrell (1985), is that all of the thematic roles associated with a verb are activated in parallel when the verb is encountered. In addition, we propose that thematic roles are provisionally assigned to arguments of the verbs as soon as possible, with any thematic roles incompatible with such an assignment becoming inactive. Active thematic roles that are not assigned arguments within the sentence are entered into the discourse model as unspecified entities or addresses. In our first experiment we show that temporary garden-paths arise when subjects initially assign the wrong sense to a verb as in Bill passed the test to his friend, but not when subjects initially assign the wrong role to the noun phrase, as in Bill loaded the car onto the platform. This prediction follows directly from our assumptions. In our second experiment we show that definite noun phrases without explicit antecedents in the preceding discourse can be more readily integrated into a preceding discourse when they can be indexed to an address created by an open thematic role

We can guide search by a set of colours, but are reluctant to do it.

For some real-world color searches, the target colours are not precisely known, and any item within a range of color values should be attended. This, a target representation that captures multiple similar colours would be advantageous. If such multicolour search is possible, then search for two targets (e..g Stroud, Menneer, Cave and Donnelly, 2012) might be guided by a target representation that included the target colours as well as the continuum of colours that fall between the targets within a contiguous region of color space. Results from Stroud et al (2012) suggest otherwise, however. The current set of experiments show that guidance for a set of colours that are from a single region of color space can be effective if targets are depicted as specific discrete colours. Specifically, Experiments 1-3 demonstrate that a search can be guided by four and even eight colours given the appropriate conditions. However, Experiment 5 gives evidence that guidance is sometimes sensitive to how informative the target preview is to search. Experiments 6 and 7 show that a stimulus showing a continuous range of target colours is not translated into a search target representation. Thus, search can be guided by multiple discrete colours that are from a single region in color space, but this approach was not adopted in a search for two targets with intervening distractor colours

Reply to letter to editor by M.J. Sankeralli and K.T. Mullen published in Vision Research, 41, 53-55: Lights and neural responses do not depend on choice of color space.: Lights and neural responses do not depend on choice of color space.

No abstrac

Posture responses to impulsive shifts of viewpoint

Visual, vestibular, and somatosensory systems provide critical information for maintaining upright standing posture. The focus of this study is how visual information influences standing posture. We investigate posture responses to left-right, forward-backward, and upward-downward impulsive displacements of visual viewpoint delivered using a head-mounted display (HMD). Impulsive changes in viewpoint position in a particular direction cause biphasic posture responses along the same direction and, if one is moving in a virtual environment (VE), along the direction that corresponds to the direction of movement. We found symmetric mediolateral responses to leftward and rightward shifts in viewpoint position. Anteroposterior responses to forward and backward shifts in viewpoint were not symmetric, and the asymmetry revealed did not disappear in a control experiment that used weak forward and backward impulsive shifts of viewpoint. No significant changes in lower-body posture occurred in response to upward or downward shifts of viewpoint, although tracking head movements in a target-tracking task were evident. Finally, the Fourier transforms of the measured impulse responses suggest that the visuo-postural response system is not sensitive to viewpoint oscillations at frequencies greater than 2Hz