The speed of scanning a page of familiar layout improved about 25% with practise, but became stationary after about 200 trials. ...Other highlights include Signal Detection Analysis of WWW Search Engines by Erik Nilsen from Lewis & Clark and Measuring User Motivation from Server Log Files by Rodney Fuller& Johannes J. deGraaff from Bellcore.
The scanning rate (time per item) for close and equidistant vertically oriented items was estimated to about 100 ms; for separated items it was estimated to about 220 ms.The scanning rate of horizontally aligned items was estimated to be 1.2 times that of vertically aligned items. This shows that vertical alignment of data is preferable and that data items within a group should be grouped close together...
The Yahoo style navbar suffers in this analysis.
The average time for comparison of adjacent numerical values was estimated to about 450 ms.
As expected, searching for a target item was significantly faster (83%) if the target item was given a unique feature, compared with if no unique feature was used. The colour, shade, space, slant and size features were equally effective compared with a control condition without features.
This offers opportunity and rationale for design!
...If the probability of finding an interesting item was non-uniformly distributed across the screen area, then this pattern of varying probability was learned by the users. The search strategies were suitably adopted and this resulted in significantly faster search (32%) than if the probability distribution was uniform. A post experimental test showed that the subjects were not consciously aware of the probability distribution, but in spite of that, the search strategies were almost optimally adapted to the pattern of varying probability. This finding reveals that even if there are many items on the screen, the average search time can still be short if the probability of finding the target item is non-uniformly distributed across the screen area, and this distribution is constant over time.
The slowest search is obtained for multiple groups of horizontally aligned items in a random order.
The fastest search is obtained when search space can be restricted by knowledge captured by the peripheral visual system. Highlighting, informative patterns and spatial constant positions are such design principles. Presenting data items in fixed positions on the screen, so that each position has a meaning, is thus useful for effective interaction.