As he [Doc] paced, he caught a picture of himself in the mirror. He was forced to smile. How outrageous he looked with this conglomeration of vacuum tubes, rheostats, gauges, wirings, and antennae on his head. It was, he was inclined to admit, the most stereotypical image of the mad scientist. But no matter. If the device proved practical in the area of mind reading, it wouldn't matter what it looked like." [Doc] —From Back to the Future by George Gipe (quote, page 114)

" Without removing his headgear — it was so much trouble to hook it up — Doc Brown strode to the door and opened it. A young man of perhaps seventeen was there. His appearance caused Brown to almost clap his hands in sheer delight, for he was clad in a shirt that was illustrated with a blowup of a patent office entry. How this appealed to the heart of a frustrated and neglected and much maligned inventor can be easily imagined. / In this happy frame of mind, Doc Brown decided to continue his experiment. He turned the switch on, waited for it to warm up, pointed his finger at the young man, and said "Don't say a word." / The young man obeyed, his mouth closing before he could get his first words out. / "I'm going to tell you your name," Doc Brown said. "Think of your name." " —From Back to the Future by George Gipe (quote, pages 114 and 115)

"My God. Do you know what this means? It means that this damn thing doesn't work at all!" —Doc

The brain-wave analyzer was one of the inventions Dr. Emmett Brown created in 1955. It was intended to allow him to read someone else's thoughts.

History

When Marty McFly arrived at his house for the first time, Doc disconnected the machine from his dog Copernicus, and tested the machine on him as he arrived on his doorstep. It consisted of a helmet with a metal geodesic framework that held several cylindrical devices pointed at his head, with electrical wires that led from each of these devices to either a small helmet strapped to his dog's head, or to a suction cup that he stuck to Marty's forehead.

His first guess was that Marty had come "from a great distance.” This was true; Marty traveled 2 miles from Lyon Estates to Hill Valley and a great distance in time. His second guess that Marty was selling subscriptions to The Saturday Evening Post door-to-door. This was a common occupation, but not entirely correct, as Marty had picked up a newspaper earlier that day to check when he was. His next guess was that Marty was selling peanut brittle — as Howard's daughter, a Girl Scout, was doing for her baseball team in 1985[1] — for the Boy Scouts,[2] which was incorrect. After noticing that Marty appeared to be wearing a life preserver, Doc made a wild guess that he was collecting donations for the Coast Guard Youth Auxiliary. He did not know that only a short time beforehand, when Lorraine's mother guessed that he was a sailor, Marty answered that he was a member of the Coast Guard.

When Doc discovered the brain-wave analyzer didn't work at all, he placed it on the desk and started examining it until Marty persuaded him to leave it alone and focus on the time machine.

A week later, while Doc was reading the letter his 1985 counterpart had sent from 1885 via several generations of Western Union, Marty tried on the brain-wave analyzer helmet as he looked at the inventions in the lab.

Back to the Future: The Ride

At some later date, Doc Brown and his team at the Institute of Future Technology successfully demonstrated a much smaller version of the brain-wave analyzer that was used to read one's own thoughts and display them on a LED screen. The device worked by harnessing electro-magnetic impulses created by synapse-disponses from both the cerebral-malbestare. Mind waves were transmitted at a mind obitting rate into the circuitry, thus translating thoughts into written form-in other words, reading your mind. Apparently Doc had some initial doubts that his newer version of the brain-wave analyzer would work, as the message on the display was that of Doc pleading to the device to "Work, baby, work!"[3]

Note: The following section is considered non-canon or is disputed in canonicity.

In 1986, during the estate sale, Biff Tannen wore Doc's original brain-wave analyzer helmet.

Non-canon or disputable information ends here.

Behind the scenes

According to the novelization, when Doc discovered the brain-wave analyzer didn't work at all, he threw it to the floor in anger:

" "What are you selling?" Doc asked. "That's how all sales pitches start." / [Marty replied] "I'm not selling anything. Listen: I'm from the future. I came here in a time machine you invented — and now I need you to help me get back." / "Back to where?" / "Nineteen eighty-five." / "Incredible," Doc Brown breathed. "My God, do you know what this means?" / He paused dramatically, then began to remove the complicated contraption from his head. / "What does it mean?" / "It means this damned thing doesn't work at all!" he yelled, throwing the machine to the floor. It broke into several pieces, glass and plastic flying everywhere. "Six months labor for nothing! Where did I go wrong?" " — (quote, page 116)

Appearances

Sources

Back to the Future novelization (regarding name of invention)