“The Hawthorne researchers became more and more interested in the informal employee groups which tend to form within the formal organisation of the Company, and which are not likely to be represented in the organisation chart. They became interested in the beliefs and creeds which have the effect of making each individual feel an integral part of the group and which make the group appear as a single unit, in the social codes and norms of behaviour by means of which employees automatically work together in a group without any conscious choice as to whether they will or will not co-operate. They studied the important social functions these groups perform for their members, the histories of these informal work groups, how they spontaneously appear, how they tend to perpetuate themselves, multiply, and disappear, how they are in constant jeopardy from technical change, and hence how they tend to resist innovation.
In particular, they became interested in those groups whose norms and codes of behaviour are at variance with the technical and economic objectives of the Company as a whole. They examined the social conditions under which it is more likely for the employee group to separate itself out in opposition to the remainder of the groups which make up the total organisation. In such phenomena they felt that they had at last arrived at the heart of the problem of effective collaboration, and obtained a new enlightenment of the present industrial scene.”

Cited in: Lyndall Fownes Urwick, ‎Edward Franz Leopold Brech (1961), The Making of Scientific Management: The Hawthorne investigations https://archive.org/stream/makingofscientif032926mbp#page/n191/mode/2up. p. 166-167
Management and the worker, 1939