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The 'Haunted Swing' illusion.

1895; American Psychological Association; Volume: 2; Issue: 3 Linguagem: Inglês

10.1037/h0073333

1939-1471

Roger Wood,

I was much interested this summer in the curious sensations produced by a purely optical illusion, known as the 'Haunted Swing,' at the Midwinter Fair in San Francisco.On entering the building we found ourselves in a spacious cubical room, furnished with a sofa, table, chairs, etc., a massive iron safe, and a piano, together with other minor articles.But the most conspicuous object was the huge swing, capable of holding forty or more persons, which hung in the centre, suspended from an iron cylinder which passed through the centre of the room.We took our seats and the swing was put in motion, the arc gradually increasing in amplitude until each oscillation carried us apparently into the upper corners of the room.Each vibration of the swing caused those peculiar ' empty ' sensations within which one feels in an elevator; and as we rushed backwards toward the top of the room there was a distinct feeling of ' leaning forward,' if I can so describe it-such as one always experiences in a backward swing, and an involuntary clutching at the seats to keep from being pitched out.We were then told to hold on tightly as the swing was going clear over, and, sure enough, so it did, though the illusion was not so perfect as the high oscillations.The device was worked in the following way : The swing proper was practically at rest, merely being joggled a trifle, while the room itself was put in motion, the furniture being fastened down to the floor, so that it could be turned completely over.The illusion was good, though the absence of centrifugal force, and the fact that the swing did not move with uniform acceleration as it descended, would indicate to a careful observer that he was not swinging freely.The curious and interesting feature however, was, that even though the action was fully understood, as it was in my case, it was impossible to quench the sensations of < goneness within' with each apparent rush of the swing.The minute the eyes were shut the sensations vanished instantly.Many persons were actually made sick by the illusion.I have met 277