To create the hallucinogenic virtual world, Suzuki and his colleagues first shot a panoramic 4K video of a bustling student plaza on the Sussex campus. They then gave each frame of the three-minute video the Deep Dream treatment. Deep Dream is an algorithm that uses artificial neural networks to transform normal images of flowers and faces into wildly psychedelic landscapes. After a week of processing, the result was a 360-degree street scene straight out of Alice in Wonderland.
In one experiment, participants watched two versions of the panoramic video in their VR headsets — the normal street scene and the altered Deep Dream version. Then they were asked to indicate whether they experienced various psychedelic sensations, such as seeing patterns and colors, floating, dissolution of self, emotional arousal, and distortion of time.
As expected, the plain version of the videos elicited few abnormal sensations, while the hallucinogenic version triggered a bunch.
The most striking result was when Suzuki compared the responses from the Hallucination Machine to the experience of people who had actually been dosed with psilocybin. They matched up almost exactly — the same distorted sense of size and space, the same visualization of patterns and colors.
The only thing that didn’t correlate was the classic distortion of time that people experience on psychedelics, when just a minute of a really intense trip can feel like an hour. In a separate experiment, participants were challenged to reproduce the exact time length of different musical tones while immersed in the normal and psychedelic VR worlds. They performed equally well in both.
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Suzuki said the negative result might have to do with the fact that they were using pre-recorded video from another location, where the participants’ only interactivity with the virtual world was rotating their heads around.
“Everyone immediately knows this isn’t real,” said Suzuki. “What I want to do next is patch through a real-time video feed from a camera on their heads. What happens if you start seeing a bunch of dots on your hands, and your real-time actions are turned into hallucinations? That might elicit much stronger reactions.”
What’s fascinating about the Hallucination Machine is not only the similarity between the effects of the virtual hallucinations and real psychedelic drugs, but also the similarities between our brains and the Deep Dream neural network that conjured up the altered images.
Google stumbled on Deep Dream as an unexpected byproduct of the race to create an accurate image search engine. Neural networks are designed to mimic how a brain learns by training to slowly recognize the shape of a bicycle or an apple among a database of a million images.
Image search neural networks are built of multiple layers of artificial neurons, with the lowest layer responsible for lines, curves, and rough shapes, and higher layers responsible for identifying component figures like leaves and hands, and the top layer responsible for tying all the clues together and deciding if it’s a tree or a boy. This is called a bottom-up process.
What Deep Dream does is move back down the neural network in the other direction. If you upload an image into the Deep Dream generator, the network starts searching for recognizable shapes in the clouds, trees, buildings, and faces. Then, instead of simply categorizing and naming shapes, it reverses directions and creates its own versions of those shapes, embedding them in the image. (The training database that Google engineers used had a lot of dogs in it, hence the ubiquitous dog heads in Deep Dream hallucinations.)
The brain uses a similar hierarchical system in visual perception, with the earliest parts of the visual cortex responsible for processing low-level features and the inferior temporal cortex handling the highest-level categories. That’s not to say that the brain always works from the bottom up.
“I believe there are people who have actual visual hallucinations who could have similar process in their brain, a top-down visual process in their visual cortex,” said Suzuki, including people who take psychedelic drugs. “That’s why they see an imaginary image on top of the real world.”