BG Chap 13 - The transformation or effects of the field
The field, in addition to the previously described components, also consists of the qualities of the mind such as desire, hatred, happiness and distress, which are interactions, representations of the five great elements in the gross body. The living symptoms, represented by consciousness and conviction, are the manifestation of the subtle body-mind, ego and intelligence. These subtle elements are included within the field of activities. Desire and other qualities are also qualities of the ātmā, for the Chāndogya Upaniṣad (8.1.5) describes the ātmā as having qualities of satya-saṅkalpa and satya-kāma. The Lord also describes (BG 13.21) that the ātmā is the cause of happiness and suffering in this world. Thus, though desire and other qualities belong to the ātmā, they are also qualities of the material mind, since they appear thru the instrument of the mind and therefore are included as effects of the field.