I'm building a small chat. Now I see but in other chats (whatsapp, facebook mobile chat, sms ...) that the arrangement is always the same:
Left: the chat partner. right: myself
Why is that?
If you look at most languages they are from left to right and the basic concept of a chat is about mutual interaction based upon the person's previous response. Hence, your responses will be driven by the response of your chat partner and hence his response is placed on the left and your response on the right since your response is driven by what he has said.
I would also recommend reading upon F shape patterns in reading since what you see here is a classic example of users utilzing the F shaped pattern to go through information i.e.
Also another question might be asked as to why the user responses are not on the same line.While the reason would be mainly due to the limited real estate spaced offered by mobiles, I also believe the fact the top left and bottom right are the primary areas of focus as the user scans across content. This is best illustrated by the Gutenberg principle of terminal areas which has this to say :
The terminal area is the bottom right area of your home page focal point. It comes from the Gutenberg diagram, an age-old concept developed by Edmund C. Arnold. It’s commonly used to optimize displays that have a limited number of elements. It divides your display into four areas. The primary optical area is at the top left, the strong fallow area at the top right, the weak fallow area at the bottom left, and the terminal area at the bottom right. The user’s eyes naturally begin at the primary optical area and move across and down the display in a series of sweeps to the terminal area.
Ok, why is your chat is always right, and the partner is left, In English you read form left to right, therefore, your focus on reading will be in your partner parts, not yours because you already know what you wrote. hence, your eyes keep looking in the left to read in comfortable way, and the other reason is to divide your msgs and partner msgs.
1- After you type text or message . The main CTA ( Send or Done or Ok ) is always on right ,so once you take action on those interactions starts on right side.
2- User tends to check their previous text before sending a new text so scanning would be easy if incoming text and outgoing text are starting from two ends.