they often begin in the lower left and take an anti clockwise curve round the image back to the lower left.
How often? The only clear example I can find demonstrating eye 'scanpaths' on a typical photograph can be found at:-http://www.youramazingbrain.org.uk/newrese.../issue2_2+3.pdf
In this example, the eye begins its journey on a roof top, upper left, moves on to a brighter spot diagonally upwards, does a bit of a clockwise
turn, then a counterclockwise turn as it moves to the lower portion of the picture and onwards.
I think it's going to be too simplistic to describe one particular path. It's going to vary enormously with the composition of the image and with the individual viewer, but it seems clear (for Westerners at least) there's a broad movement from left to right.
This can be demonstrated most graphically by imagining a set of unattached stairs in the shape of a triangular block. If the lowest step is at the lower left of the page and the highest step at upper right of page, then the viewer is likely to describe the object as a set of ascending
If the image is flipped horizontally so the lowest step is at the bottom right of the page and the highest step is top left of the page, the viewer is then likely to describe what he's seeing as a set of descending
However, for Arabs (assuming literacy and not too Westernised) the reverse descriptions would apply because they read from right to left.
The Chinese situation is interesting because traditionally they read in columns from top to bottom and right to left but have also adopted Western methods of left to right. So in Taiwan, so I believe, street names are sometimes written left to right, or right to left, or top to bottom.