In this experiment conducted in 1920, educational psychologist Edward Thorndike asked two commanding officers to evaluate their soldiers in terms of physical qualities (neatness, voice, physique, bearing, and energy), intellect, leadership skills, and personal qualities (including dependability, loyalty, responsibility, selflessness, and cooperation). His goal was to see how a persons judgement of one characteristic affected their subsequent judgement of other characteristics.

Thorndike discovered that when commanding officers gained a good impression of one characteristic from a soldier, those good feelings tended to affect perceptions of other qualities. Conversely, if a soldier had a particular "negative" attribute picked up by the commanding officer, it would correlate in the rest of that soldier's results.

The 'halo effect' refers to the positive impressions that people get about one particular characteristic affecting perceptions of other qualities. For example if you find somebody to be physically attractive, it can lead to skewed favourable perceptions of their other qualities such as generosity, friendliness, intelligence etc. However the reverse is also true. If you get negative impression of one characteristic it can lead you to view other personal qualities in a less favourable light. First impressions count!