Conjunction fallacy

A conjunction effect or Linda problem is a bias or mistake in reasoning where adding extra details (an "and" statement or logical conjunction; mathematical shorthand: ${\displaystyle \land }$) to a sentence makes it appear more likely.^[1] Logically, this is not possible, because adding more claims can make a true statement false, but cannot make false statements true: If A is true, then ${\displaystyle A\land B}$ might be false (if B is false). However, if A is false, then ${\displaystyle A\land B}$ will always be false, regardless of what B is. Therefore, ${\displaystyle A\land B}$ cannot be more likely than A.