Manipulating someone psychologically such that they start to doubt their own sanity. Lying or deceiving persistently can plant seeds of self-doubt in the minds of someone else. At first, it is likely to be easy to resist, but if it continues people can start to question their own reality or start to think they may be going crazy.

The term comes from the play Gas light by Patrick Hamilton where a husband tries to convince his wife, played by Ingrid Bergman in a 1944 film adaptation, that she imagined the dimming of gas lights in their house, which was, in fact, due to him searching for jewels in the flat above.

The term has been used in sociological, psychiatric and political contexts among others.

Gaslighting

UPDATE: Since releasing this sketch, which is a fair summary of Kamal Meattle's TED talk, it's been made clear that, though plants do improve air the improvement doesn't compare with a simple change like opening the window. The original "plants improve air quality" study was done by NASA in an environment wholly unlike having a few plants in your living room. Listen to James Wong explain the situation in the Sketchplanations botany podcast.

In his 4 min TED talk, Kamal Meattle explains how to grow your own fresh air inside with just 3 common house plants. The areca palm works hard during the day, the mother-in-law’s tongue during the night, and the money plant cleans out volatile chemicals. He transformed the air inside a New Delhi office park by filling it with these three plants with seemingly some wonderful health and productivity benefits.

Though plants are undoubtedly lovely to add to your office and home, see the update above for the caution around it.

How to grow your own fresh air

The Oxford comma is the comma after the penultimate item in a list. It’s normally a matter of style — you can happily choose to leave it out — though in some cases it can clarify what would otherwise be an ambiguous meaning, as in this well-cited book dedication “To my parents, Ayn Rand and God.” Or, more pertinently, in a recent legal case where ambiguity hinging on the lack of an Oxford comma is costing a dairy firm a $5m overtime payment to its drivers.

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The Oxford comma