Just a few half-baked thought fragments on why social psychology is important when we are designing for computing technology: Often, computing technology conveys some sort of social presence. Resulting to that fact people do respond to this technology often as though the technology item is a social entity like eg another human (For reference on that see e.g Reeves, B. and Nass, C. ;1996. The Media Equation: How People Treat Computers, Television, and New Media Like Real People and Places, Stanford University)
Here are a few examples how social presence is conveyed (among other things):
Fig 01: Keepon, a social robot/beatbot for autistic children
Keepon is a computing technology in form of a robot. It conveys social presence for us humans through (obvious) physical cues like a face. It has eyes and also some physical skills like it starts dancing/moving and making funny noises when it listens to music or when you interact with it.
Fig 02: Siri, a voice based digital assistant
Also voice based digital assistants like Siri convey – in this case despite their very futuristic and techy appearance – social presence through language cues but also through social roles like gender which we implicitly perceive. We will imply implicit assumptions and personality behind it – despite we are knowing it is a machine.
Fig 03: Unhelpful error message found in moodle a while ago
But of course, also technology with no obvious physical cues like faces or other cues like voice/spoken language at all can convey social presence. For example simply in presenting an error message, respectively by using written language/plain copy to communicate with a human. The example error message above is not providing any helpful hint what exactly has happend / has gone wrong and also it uses a strange language (It says: Error found. Error only could be removed by a programmer. Course not usable) – so I will attribute this behavior to the product/company behind it: eg they are blaming me for that error only a programmer can remove, so they are unhelpful and they dont care about me /their customers/users etc.
So in all these cases theories provided by social psychology research can serve as valuable guidance when designing interactive products or any computing technology.