Wednesday, June 24, 2009

Foveal Vision and Peripherial Vision Teamwork

Journal Entry 6/22/09: Weight = 176.0; Coinage = $.36, 11 pennies, 1 quarter—a one bagger; Glass bottles =4; Ground Score = 3. Recently walks have produced several recyclable clothes, could it be the heat? Even for New Orleans, the heat index is + 100° which is rare given the usual cooling breeze off of Lake Pontchartrain.

Journal Entry 6/23/09: Weight = 174.0; Coinage = $1.23, 28 pennies, 2 nickels, 2 dimes, 3 quarters (a 3 bagger); Glass bottles retrieved = 7; Ground Scores = 4. Best find = two quarters from an AT&T pay phone that prior to today had given no return. Just before, a loquacious observer at another pay booth had replied, “Those machines don’t give money anymore.” She was proved wrong, but the MoneyWalker must be more discreet.

Feature Entry: Finding a coin is a team effort between two aspects of the visual process—the foveal receptors and the peripheral processors. The foveal receptors compared to the peripheral’s allow a very narrow scan range, thus they are called upon for specific focusing and identification. Peripheral receptors are used for location and general orientation. They have a broad “field of vision,” about 160° horizontally and 135° vertically. Therefore, the peripheral receptors locate a coin and the foveal receptors identify it as coin rather than a “false positive” such as a flattened bottle cap or discarded cell phone battery.

As might be expected, the foveal receptors require conscious control for accuracy, thus are costly in terms of attention. When using foveal vision, the walker must stop, examine the stimulus pattern, make a decision as to coinage or imitator, and then either retrieve or move on. The peripheral processors work rapidly, require little central processing, but are not accurate. Their job is to locate all generally round objects in their field of vision and pass the information to more central processors. When cued, often subconsciously, these centers alert the foveal receptors that something specific is in the area requiring attention.

And the teamwork continues on and on until the walk is over.

Back to Monday’s feature about posture. If the walker is hunched over, with glaze downward, probably an overreliance on foveal vision is occurring. Instead, use the upright balanced walking posture with eyes scanning 10 to 15 feet forward and downward. Scanning is a back and forth movement with peripheral vision receptors on full alert for roundness. When roundness is spotted, the brain quickly consults foveal receptors for update. If coin is confirmed; the task is to stop and retrieve.

But then, be very cautious. A second coin even ten inches away can be overlooked. The original coin is what grabbed the foveal receptor’s attention, not the second coin. Once a coin is found, the system is in “buzz” mode (celebration) not searching mode. Cognitive override is required. The thinking part of the brain must tell the visual part to carefully search the area around the coin find for other coins. Amazingly, what frequently happens next are secondary coinage finds. Even with my best effort, the Moneywalker has returned to these spots on future days to find even more coins that were missed, even with conscious effort to look carefully during the original find.

DaNaw, DaNaw, DaNaw …..are we in the twilight zone yet?


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