The mental alignment meter was a device invented by Emmett Brown in 1931 at the urging of his girlfriend Edna Strickland. It consisted of several parts: the mind mapping helmet, a typewriter and the M.A.M. itself. It had the ability to read the subconscious desires of the human mind.
In the 1986B timeline, Emmett went through with submitting this invention in the Hill Valley Science Exposition and won, starting him on the path that, under Edna's guidance, would cause him to turn Hill Valley into a police state.
The helmet read the mental patterns of the wearer as he/she viewed certain images, detecting a positive, neutral, or negative reaction in the wearer. As the next image was cued up, these mental patterns were converted into coding for the typewriter as it punched holes in exact places in a strip of paper. The paper, now a "mind map", would be inserted into a slot in the M.A.M., which would read the pattern of holes and display what mental state the subject was in. The levels of morality the machine could interpret were, in this order, as follows:
- Model Citizen
- Honest Joe
- Decent Chap
- Inveterate Liar
- Degenerate Criminal
The following images for the mind map test were as follows:
- Edna Strickland
- John Wilkes Booth
- Danny Parker
- Beauregard Tannen (Referred to as a Tannen when putting the cursor over the photo.)
- Gerald Strickland (as a young child)
- Trixie Trotter
If the person being tested disliked all of what the M.A.M. was programmed to display as "right", he or she would have a mind map showing a Degenerate Criminal, while going with the "correct" responses resulted with a map that indicates a person to be a Model Citizen. It should be noted however that what was set as "right" or "wrong" was entirely according to Edna Strickland's sensibilities.
Most of Marty's responses weren't shown, but he had a negative response to Edna, while showing a positive response to Trixie. His mind map read as a Layabout (which Marty interpreted as a slacker).
When Marty McFly was in 1931 attempting to break up Edna and Emmett in order to preserve the future, he created a new mind map for Brown through manipulating the responses the distracted Emmett (still wearing the mind mapping helmet) was providing for the assigned images, triggering positive ones for negative images and vice versa. This produced a 'Degenerate Criminal' version more in line with gang leader Kid Tannen, that Marty then swapped for Brown's original 'Model Citizen' mind map. After Emmett was framed with the allegation of cheating on Edna, a situation orchestrated by Marty, the bewildered Brown tried to prove his innocence by displaying his mental reading to Edna. When he placed the mind map believed to be his in the mental alignment meter, however, the machine showed a degenerate criminal. Disgusted, Edna immediately dumped Emmett and walked off, causing time to run its course on the right track.