How does a Torso of a Rakshasa speak in human language? We encounter other examples of lower order beings communicating with humans in Puranas. Patanjali covers the topic of the ability of lower order beings to communicate with humans in his treatise called Patanjala Darshana. Patanjala Darsana discusses the question of a soul migrating from a human or higher form human to a lower form. A soul carries Samskaras from one birth to the next. Samskaras include linguistic impressions. A being's intelligence may be either partly or wholly lapsed per the strength of Samskaras from its earlier life. Its audiable language (Dhvanyātmaka) can be a partly veiled human language (Varṇātmaka). Texts such as this will fascinate even those who don't believe in rebirth. Indians researched on the topic of consciousness with scientific rigor.
Kabamda story is a study on this. Kabanda was a Gandharva in his earlier life. He took the body of Rakshasa because of a curse. Kabanda did not have the ability to communicate the hint about Sita because his intelligence was muted. Gandharva intelligence in him recognized that Rama was in search of his wife. Kabanda got his original body when Rama and Lakshama buried his Rakshasa body. He then asked Rama and Lakshmana to go meet Sugriva and other monkeys.