Search

We present a method for measuring gait velocity of older adults using data from existing ambient sensor networks. Gait velocity is an important predictor of fall risk and functional health. In contrast to other approaches that use specific sensors or sensor configurations, our method imposes no constraints on the elderly. We studied different probabilistic models for the modeling of the duration and the distance of the indoor walking paths. Experiments are carried out on 27 months of sensor data and include repeated assessments from an occupational therapist. We showed that gait velocities can be measured with low variance and correlate with most assessments. The advantage of our monitoring system is that because of the continuous measurements, clearer trends can be extracted than from incidental assessments of the occupational therapist.

Does form discrimination rely on feature analysis, as the indirect theory of perception supposes, or on affordances (behavioural meanings specified by invariant patterns), as direct theory states. Subjects were to indicate the position of a target in a perspective rendering of a plane, displayed for 100 msec. in a large screen projection. In one of the conditions the target disrupted the plane, in the other it did not. Although targets of the two conditions shared the same features, the disruptive targets were discriminated more often than the nondisruptive targets. This result supports the direct approach to perception which states that a perceiver discriminates behaviourally relevant patterns rather than geometrical properties.

Contemporary literature suggests that preattentive texture or pattern discrimination is induced by differences between local structure features or “textons”. This paper presents a model for the description of such local structure features based on the computation of local autocorrelations within the image. By means of this structure model a measure of structure dissimilarity is introduced. Experiments have been carried out to test a hypothesized relation between the detectability of a target pattern in a field of background patterns and the value of the structure dissimilarity measure. The experimental results show that it seems justified to relate, in a quantitative way, the detectability of the target pattern to the value of the structure dissimilarity measure.