This question is a lot of fun. It is always entertaining to ask bizarre questions to Siri, and sometimes we will be rewarded with hilarious answers. For instance, try asking Siri out for a date.
However, your question does indeed have a lot of philosophical grounding. And that is the philosophical question of how do we know when Artificial Intelligence (AI) is actually thinking like us human beings are. Another way of thinking about this, is the question of whether AI is self-aware, or conscious.
The most commonly known attempt from this question comes from Alan Turing, known as ‘The Turing Test’. The Turing test is, roughly, that a person is to engage with an AI, without knowing prior whether they are talking to an AI or a human being. If the AI can convince the human that they are talking to another human being, then the AI has passed the Turing Test, which is to conclude that the AI is thinking just like a human being.
At this stage, I think we would agree that Siri cannot yet pass the Turing Test. However, even if she did, philosophers have pointed out that the Turing Test does not tell us if AI is thinking just like human beings regarding being self-aware or conscious. The most powerful objection comes from John Searle. Searle puts forward a thought experiment called ‘The Chinese Room’. In the thought experiment, a Chinese person in a separate room slides messages written in Chinese under the door to a person in another room. The other person doesn’t understand Chinese, but has been given a code to respond to Chinese words by corresponding them with other Chinese words. Using the code, the person can return the correct messages back to the Chinese person. So, even though the Chinese person thinks they are recieving messages from someone who understands Chinese, they actually are not.
This thought experiment demonstrates just because something can behave just like a human being, does not mean it is thinking like a human being. So, when we ask Siri how she is feeling today, poor Siri is probably lying.