Orientation integration in detection and discrimination of contrast-modulated patterns

Orientation detection and discrimination thresholds were measured for Gabor ‘envelopes’ formed from contrast-modulation of luminance ‘carriers’. Consistent with previous research differences between carrier and envelope orientation had no effect on sensitivity to envelopes. Using plaid carriers in which the proportion of contrast modulation ‘carried’ by each plaid component was systematically manipulated, it was shown that this tolerance to carrier-envelope orientation difference reflects linear summation across orientation indicative of a single second-stage channel coding for contrast-defined structure. That contrast envelopes did not exhibit linear summation across spatial-frequency, nor across combinations of orientation and spatial-frequency differences, suggests that these second-order channels operate only within certain spatial scales. Using arrays of Gabor micropatterns as carriers in which the orientation distribution of the carriers was manipulated independently of the difference between envelope orientation and mean carrier orientation, it was further demonstrated that the locus of orientation integration must occur prior to envelope detection. In the context of two-stage models that incorporate a non-linearity between the stages, the pattern of results obtained is consistent with the operation of an orientation pooling process between first-stage and second-stage channels, analogous to having all filters of the first-stage feed into all filters of the second-stage within the same spatial-frequency band.

The role of local grouping and global orientation contrast in perception of orientation-modulated textures

We explored the contribution to perception of orientation-modulated textures of visual processes selective either for orientation contrast or orientation grouping. To distinguish between these two processes we manipulated the axis of local grouping of texture elements independently of the direction of global orientation modulation. The general question posed was whether visibility of texture structure (measured as threshold for discriminating spatial-frequency of texture structure) is dependent on the magnitude of orientation contrast, strength and direction of local grouping, or some combination of the two. We demonstrated that the factor of primary importance is the amplitude of global orientation contrast rather than the presence of local grouping content. Using orientation-interleaved textures (containing two superimposed textures modulated around orthogonal orientations), we further showed that orientation single-opponent processes are a more likely candidate for detecting orientation contrast than double-opponent processes.

Spatial growth in Australian homes (1960–2010)

The average new Australian home has grown from a four-roomed Victorian timber cottage of around 100 m2 at the start of the twentieth century to a 245 m2 brick-veneer house in 2011. The homes have grown in both size and number of rooms. Where has this growth occurred? How has Australia's average new house transitioned to now become the largest in the world? This paper traces where the growth has occurred within the house over the last 50 years. Thirty-nine houses in a suburb of Geelong, Victoria, have been analysed over the five decades, and the median house of the sample in each era has been used for the analysis. The results confirm the overall trend in house growth size that can be seen in national statistics. Most of the growth in house size has been due to the increase in living areas and in the number of and area used for bedrooms. Other variables of interest in understanding changes in Australian housing such as gross floor area, plot ratio, site size and house shape and orientation are also discussed in the context of limiting the impact of oversize houses.