In terms of what exactly a collective experience is, it is an experience that is shared by more than one person, as opposed to an individual experience, which is only experienced by one person.
Collective human experiences are any experiences that we go through together in a group unit. From the local sports team, to the House of Representatives or a certain cultural group, collective human experiences are unavoidable and play a powerful role in influencing us as individuals.
In terms of 1984, you can say that this text explores a collective and tormented human experience, which can be expresses as the following:
Orwell’s politically charged novel, Nineteen Eighty-Four emphasises his perspective of a bleak and tormented human experience as a product of totalitarian leaders utilisation of surveillance technology and propaganda eroding individualism.
The atmosphere was characterised by multiple authoritarian leaders, including Hitler and Stalin, who employed debilitating measures in order to control the masses.
In terms of specific examples within the text, there are different techniques/literary devices used, such as the following:
Lexical choice: ‘In the end…’ exudes the party’s everlasting power
Paradox: 'thoughtcrime literally impossible’ - How can a controlling entity monitor individual thoughts?