Art and science aren't distinctly separate provinces; they sometimes overlap. When they do, the science in art is usually more apparent than the art in science. Such is the case with a four-artist exhibition at the Delaware Art Museum called "Perception/Deception."

As with trompe l'oeil painting, the show demonstrates how easily the eye - or more accurately the brain - can be fooled by meticulously crafted visual illusions.

The four artists involved - Chul-Hyun Ahn, Larry Kagan, Robert Lazzarini, and Mary Temple - use different strategies. Yet all remind viewers that what one sees in an art gallery shouldn't always be believed.

The Korean-born Ahn is the master of deception here. His four installations are all variations on the tried-and-true illusion called the infinity tunnel. This is a trick you can do at home; stand between two mirrors, and you will see your reflection replicated deep into illusionistic space.

Ahn constructs his installations with standard fluorescent fixtures and mirrors. One is a floor piece that suggests a deep, vertigo-inducing pit. Another features a glowing, open-centered square hovering in recessive darkness.

While all his work feeds off the physiology of vision, the glowing square's meditative quality makes it the most artful, like a Rothko painting.

Temple's wall paintings tap into physiology through memory. Her images of trees and other foliage are like giant pentimenti, so faintly monochromatic that one isn't sure they're real. Memory of what nature looks like and imagination help to confirm their materiality.

Lazzarini's sculptures of guns and his printlike perforated targets - distorted copies of "realistic situation targets" that depict humans in threatening postures - warp reality as one might see it in a fun-house mirror.

Particularly with the sculptures, the viewer's brain must struggle at first to reconcile the distortions with normal three-dimensional reality. Again, this is a perceptual exercise that would be at home in a psychology lab.

Kagan's wall sculptures are the most ingenious and fascinating in the way they use abstract metal constructions to create shadows that are both realistic images, mainly of mosquitoes, but also extensions of the circles and arcs that make up the sculptures.

Stragetically placed spotlights animate the metal; without targeted light, half of each work disappears.

One marvels at the calculations required to make these illusions work. Even when one looks at each piece closely, it's still difficult to grasp how the magician pulled off the trick.

The ultimate question is whether science or art has the upper hand in these strategies. Or, put another way, are these works more interesting as art or as science?

Ahn and Lazzarini appear to rely more on science; their creations are engrossing mainly as complex optical illusions.

Kagan's sculptures, by contrast, are all art, although, as noted, there's considerable premeditation involved in organizing the compositions and aiming the spotlights. The appeal of Kagan's work is primarily aesthetic, albeit with a strong element of "how did he do that?"

Temple's ethereal paintings, created from projections, lie somewhere between these poles. They rely heavily on the physiology of memory to fill in missing or dimly perceived visual information, yet they aren't, strictly speaking, mere visual sleight of hand.

"Perception/Deception" invites considerable interpretational latitude and intellectual stimulation, which is what makes it fascinating beyond the level of performance. Even when you understand the tactics, you still find yourself being drawn into the world of, Now you see it, or do you?

Potpourri of folk arts. Had I parsed the exhibition title correctly, I wouldn't have been surprised when I walked into "Making It Better: Folk Arts in Pennsylvania Today" at the James A. Michener Art Museum.

The key word here is "in," which registered in my brain as "of," which meant I expected to see mostly artists and artisans such as Ken Ely of Susquehanna County, who builds and restores dry fieldstone walls, and David Castano, a wood carver who lives in Potter County.

Both satisfy the expectations for "of Pennsylvania"; they're natives of the commonwealth who practice indigenous crafts of the type one expects to find in a primarily rural Northeastern state.

However, the label says "in Pennsylvania," which translates instead into a broad variety of folk traditions indigenous to other countries, continents and cultures, from Eastern Europe to West Africa to Southeast Asia.

The exhibition seeks to "educate visitors about the vitality of living folk-art traditions found in the Commonwealth." These traditions "are thriving and meeting the needs of communities today."

In other words, the show is a classic melting-pot display that ranges from Vietnamese funerary paintings to beaded dance costumes from southern Sudan to elaborately painted Ukrainian Easter eggs (pysanky) to examples of contemporary blacksmithing.

There's even a painting that artist POSE II describes as grafitti art, although his work is far more accomplished than that term implies, and transcends the concept of folk art.

So do Diana Meng's Chinese brush paintings, which clearly belong to fine art. So do Castano's tiny coal miners, survivors of a 2002 mine cave-in. Suffused with emotion rooted in history, this multiple-element tableau is easily the strongest piece in the show.

On the other end of the scale, some of the work on view is hardly art at all but highly skilled artisanship. like the five-foot-long stone wall that Eli constructed in the gallery.

It's a splendid example of craftsmanship - one of my show favorites, in fact - but calling it folk art is either marketing or wishful thinking.

The traveling show, organized by a coalition of cultural organizations in the state, squeezes more than 30 artists into the museum's Beans Gallery, which is a handful too many.

Yet ultimately the crowding doesn't matter because this is a candy-box "kumbaya" sampler, not a focused aesthetic argument.

It's enough, I suppose, that visitors can be impressed and delighted by the variety of creative imaginations and manual skills that have found a home throughout the state.

Art: Artistic Illusions

"Perception/Deception: Illusion in Contemporary Art" continues at the Delaware Art Museum, 2301 Kentmere Pkwy., Wilmington, through Sept. 25. 10 a.m. to 4 p.m. Wednesdays- Saturdays, noon to 4 Sundays. $12 general, $10 for visitors 60 and older, $6 for students with valid ID and visitors 7 through 18. Free Sundays. 302-571-9590 or www.delart.org.

"Making It Better: Folk Arts in Pennsylvania Today" continues at the James A. Michener Art Museum, 138 S. Pine St., Doylestown, through Aug. 28. 10 a.m. to 4:30 p.m. Tuesdays-Fridays, 10 to 5 Saturdays and noon to 5 Sundays. $12.50 general, $11.50 for seniors, $9.50 for college students with valid ID and $6 for visitors 6 through 18. 215-340-9800 or www.michenerart

museum.org.

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Contact contributing art critic Edward J. Sozanski at 215-854-5595 or esozanski@phillynews.com. Read his recent work at http://go.philly.com/

edwardsozanski.