Conversation interface with health expert: Mail-like or Chat-like?

Question

I'm building a product where a patient talks to a health expert over their smartphone. Characterstics of the conversation:

• Conversation goes on over a year (more long-term than, say, a conversation with a customer support)
• Response time of the expert is within 24 hours, only on week days
• Every patient has one health expert assigned. One expert manages multiple patients
• Only a single long conversation, not multiple subjects / threads of conversation
• It will exist on iOS and Android

I'm wondering what the best interface is on the patient side.

I see 2 main directions:

1. Mail-like: Like a thread in Gmail, Inbox or Apple Mail. The conversation is a list of messages that are usually collapsed but can be expanded on tap. To compose a message you tap a dedicated icon, a new dialog shows up in which you write the message.
2. Chat-like: Like a chat in iOS Messages or Whatsapp. The conversation is a list of messages that are fully visible (not collapsed). To compose a new message you tap into a compose field at the bottom of the screen. Messages tend to be short because the compose field is small.

What's the right choice?

Answer 1

The main difference between the two is the ability to collapse/expand a message. The advantage of this is that the user can navigate fast to an specific message and keep track of the conversation with a bigger view of the context. Compare these two images:

Note the empty space in the email-like image that could be filled with more collapsed messages.

• If the user will want/need to locate a specific past topic (a list of messages) the email-like option will probably be more suitable.
• If the user won't need the former feature (nor keep track of the topics that have been discussed), having to expand immediate-past message will be more annoying than useful.

Answer 2

I would suggest chat. Besides the better indication of the two sides of the conversation (me - right side, them - left side) you will get a feeling of a higher immediacy of the whole conversation.

Chat also feels "closer" to the other side than "threaded mail" would, so there are fewer cognitive constraints about it. (On the other hand, in a thread-like model you could expect more detailed information to be sent, especially from the User to the Expert.)

And especially in this particular kind of personal conversations, like those about your own health, you would expect both the other side being rather "closer" and the answers from them being rather "immediate".

The only thing I would be careful about is that by this immediacy feeling, Users may get a little bit disappointed if the answer comes back after several hours, so not really immediately. Should you face this kind of situation, you may need to go for the threaded model anyway.

However, you could also consider communicating the delay time or, eventually, making it in fact more immediate (so it would be service design, that could even involve adding some chatbot to the process - just guessing).