by Peter Kinsella
Spanish doctor Francisco Belda Maruenda is reported as having discovered why offside decisions in football matches are often controversial.
He reckons that for the rule to be applied accurately, the referee and linesmen need at least five moving objects in their visual field at the same time - the ball and two players from each team. But the human eye and brain simply cannot process all the necessary information and then make an instant, correct decision, he reports in the British Medical Journal. Dr Maruenda's interest in what is known as 'visual processing' is shared by researchers in the UK, where related work has taken place with funding from the ESRC.
It is already known that the time we take to count how many objects there are in a display is much the same for up to about three or four items, but after that, it increases dramatically for each additional object we have to take account of.
...the human eye and brain simply cannot process all the necessary information and then make an instant, correct decision...
One theory is that our sight system has about four 'tags' which it can place onto objects we are observing. When it comes to looking at more than, say, four items, our mind has to re-assign those tags between them, so while counting up to four is quick, counting more than that is much slower. We know also that when we look at a display of items, the ease at which we find a single object (or target) depends on how similar it is to the other items (or distractors).
Researchers at the University of Warwick investigated the effects of old age - both normal and when suffering from Alzheimer’s disease - on counting (or tagging) of multiple items. They concluded that age had little effect on counting items on their own; finding a single highly distinct object amongst others; or counting about four or more easy-to-find objects amongst distractors. But older people were less efficient when it came to such things as counting up to about three or four 'targets' amongst other items (even if finding a single object was easy) and counting small or large numbers of difficult-to-find objects.
Our eyes - or, rather, eye movements - were also at the heart of research into how drivers make judgements in order to avoid collisions. Clearly, this is critical, particularly where cars enter a line of traffic from a side road. It means being able to estimate your position relative to the oncoming vehicle as you approach the junction.
Researchers at the University of Nottingham found that drivers made frequent eye movements between the approaching car and the road ahead. Where there was a road sign, occasionally the eyes became fixed on it, but there were no significant changes in the overall pattern, suggesting the road sign did not play an important role.
Early analysis suggested that drivers used the edge of the intersecting road as a reference point to estimate the remaining distance. Gender differences were not originally part of the investigation, but men were found to be significantly more accurate than women in their timing judgements.