When I’m at the beach, I do things slowly, and I take my time doing them (meaning, I’m slow to stop one and turn to another).  My wife and I have spent six weeks over in the past seven years in the same beach town (we’re working on week seven) and have not yet eaten a meal out in that town.  (We have managed lunch in another town — twice so far in those six weeks.)

I do a lot of reading, and one of my take-alongs this trip has been Foundations of Cognitive Psychology: Core Readings, edited by Daniel Levitin (author of This is Your Brain on Music).  Part 5 deals with perception, and I just finished a chapter on how the brain organizes objects and scenes.  The section is taken from Stephen E. Palmer’s Vision Science: Photons to Phenomenology.

It’s fascinating to read how scientists try to work out how the brain perceives objects.  How does it know that part A belongs with part B?  (Answer: well, it doesn’t , but it’s good at guessing… and at learning from the outcomes of the guess.)

For example, here’s the classic gestalt psychology principle of grouping by proximity: all things being equal, objects that appear close to other objects are taken to be grouped with those objects.

Palmer and others have developed a common region principle, under which the brain tends to group together objects located within the same closed region.  Compare the three examples below with (b), above.

What does this have to do with my being at the beach?  As someone said, “in theory, there’s no difference between theory and practice… but in practice, there is.”  I’ve learned through experience that the best time for long walks near the water is after high tide.  The tide’s going out, and the sand nearest the water’s edge is firmly packed.  I don’t have to trudge like French legionnaires on their way to relieve Fort Zinderneuf.

I found tide tables online, put them in Excel, and printed out the results to leave near the door:

The result?  I keep mistaking high tides and low… the symmetry of the chart means I can’t tell at a glance whether “LOW” goes with the time to its left, or the time to its right.  Thanks to my reading, it only took me three days to come up with the solution:

Grouping principle illustrations from ScholarPedia.