Last night, I went to the symphony with my good friend Jess. We had to rush out of the late afternoon talk we had heard Drucilla Cornell give at Emory because Jess had looked at the tickets and found that they said 7 pm, rather than 8 pm as she’d originally thought. We scurried off and weaved through Atlanta rush-hour and cursed the slow-moving suburban in front of us, skidding into a parking spot, darting up to the elevator (with Jess nearly getting taken down by a tiny car also rushing into the parking garage– leading a nearby man to scoff, “Almost hit by a SmartCar, how embarrassing!), and entering the music hall just a minute late.
The woman who handed us programs whispered, “You’re too late to sit on the stage, but you can have any seat you like.” Nice joke, I thought. The music hall was almost empty, so we decided to take her advice and sit front and center rather than take our seats in row L. I felt bad for the orchestra, having such a tiny audience. As we took our new seats, I thought, “they sure are dressed down tonight– that’s strange,” as a man seated onstage in a gray suit jacket and pink bow tie caught my eye. No white tie and tails for the orchestra tonight! And then, I noticed that the woman singing in the middle of the stage was…facing away from the audience. Jess and I wondered, are they still rehearsing? We looked at our tickets, and it said 7:00.
It took us nearly a full aria to analyze our tickets and realize that the 7:00 performance was a preview and the real show started at 8:00. The people onstage were other civilians, like us, who were invited to sit in the musicians’ seats while they took in a preview of an upcoming performance at the symphony: a soprano and a string quartet doing Beethoven.
At which point Jess and I ducked out quietly and headed to the lobby for a drink.
What struck me about this experience was how long it took us to figure out what was going on. Or, put differently, how long it took us to figure out that there even was something amiss. Rather than walking in, perceiving instantly that the opera singer was turned around and that (aside from the string quartet surrounding the singer) everyone onstage was a symphony-goer and not a member of the orchestra, it took me minutes to gradually figure out each piece that finally led to me recognizing what was up. It took an overwhelming amount of evidence pressing upon my perceptions to counterbalance my assumption that I was going to see a 7:00 performance by the symphony.
An oft-mentioned psychological phenomenon is that of “change blindness.” The basic idea is that, when focused on a particular part or set of parts of our field of vision, we can be entirely blind to changes in other aspects of that field of vision even when they change drastically.
This related video changed my life when I saw it in Psych 101:
In the case of the symphony, I didn’t experience change blindness, but I did experience the related phenomenon of approaching a situation with certain beliefs about what it was going to be like, beliefs that were so unconsciously strong that they actually prevented me from perceiving my surroundings as they were. I only realized after Jess and I figured out that this was a 7:00 preview of a different performance before our 8:00 show that it dawned on me that the people onstage not only were not playing instruments, they did not even have instruments! I was shocked that I didn’t notice this right away. Sure, there are certainly times when much of the orchestra is not playing their instruments– when a flute is soloing, or the oboes are doing their bit– but no one even had instruments! Or music! I was completely blind to this omission. And I interpreted the “orchestra’s” casual wear as a befuddling aesthetic choice, rather than instantly recognizing that because the men weren’t wearing white ties and tails and the women didn’t have on tasteful black numbers, this might not actually be an orchestra’s performance.
We often tend to think of our perceptions as taking in the world around it as it is. But it’s experiences like these that force one to recognize that there is in fact a complex interrelation between our habits, assumptions, and ideas and the way that we actually perceive the world around us. When I perceive, I am not passively taking in things around me. I take part in constituting the perception of the world around me (leading many philosophers to leave out the middleman and argue that, in fact, I take part in constituting the world around me), and this constitution occurs at an unconscious level every second of my life.
One philosopher to really emphasize this constitutive nature of perception is Edmund Husserl, the founder of phenomenology. He says of perception:
“Every perception of a physical thing has, in this manner, a halo of background-intuitions…and that is also a “lived experience of consciousness.” 
 Edmund Husserl, Ideas pertaining to a Pure Phenomenology and to a Phenomenological Philosophy, section 35.