I felt I should probably qualify the tweets before anything else. My tweets were really just the slides of the talks with not much editorial. This meant that I didn't really tweet of what Birgit was saying. Ironically, given the subject at hand, this meant that her motivation for showing the slides was probably missing from the tweets.

My take from Birgit's talk was more about tweaks to the environments and systems people were living and working in in order to nudge their behaviour rather than the carrot-stick paradigm. She has a psychology background and prefaced that equation with "this is what my psychology Prof. always used to say to me", which probably explains why its out of date.

That aside, I agree with what you are critiquing because I also raid the psychology bookshelves regularly (thanks to a psychologist wife!). Motivations are more complex that simply behaviours, actions and environments. Behavioral psych has a whole history behind it whose motivations are also worth examining because it is bound up with the field of psychology positioning itself as a 'proper' science over the years and – in undergrad and postgrad teaching at least – has focussed heavily on "stats and rats".

Poking stickelbacks with sticks (or rather, showing them painted sticks that look like other ones) to see what they do might tell you behaviour and needs, but it doesn't tell you much about their motivations and/or goals. If they could talk, we'd do ethnographic interviews with the stickelbacks and ask them about their lives, but we can't. Much of that research got transferred or generalised to human actions, goals and behaviours.

I don't think that makes it all non-valid for service design (or interaction/experience design in general) but, as you point out, service design's special twist is really about uncovering those motivations and goals, many of which are unknown (at least explicitly) to the person who has them. It's a much more complex picture, especially as the 'environment' often comprises relationships with other people, who may also not be aware of their underlying motivations. This increases the complexity of the situation by many orders of magnitude.

We get to see someone in context exhibiting behaviour or expressing ideas and desires and goals that give us insights into what we me might be able to do to help them achieve some of those. We get to ask why those people do the things they do, and keep asking why until we uncover some insights. Let's not forget too that service design also uses that information to further the needs of whoever has commissioned the service design – it's not always as user/customer centered as we like to make out.

This conversation uncovers an issue at the heart of much of this crossover of design with social psychology, ethnography, etc. On the one hand, I'm happy to see designers of all flavours plunder these disciplines – for plundering it tends to be (and I'm as guilty of this as any other). Theories and methods are there to be tried, tested and used and if the usage produces useful results in practice, it's less relevant whether or not they strictly adhere to the original methods or theory. It's easy to slip into dogmatic thinking, which doesn't usually give rise to innovation.

The danger, however, is when that kind of methodological plundering is then generalised back into a theory. There is no doubt that ethnographic techniques, for example, are very useful in service design and user centered design approaches. But they're a tiny sampling of ethnographic techniques, not true ethnography. That's fine in my opinion – often client, time or budgetary constraints don't allow for anything deeper and most of the time doing some research is better than nothing at all. But it's easy for new disciplines to create generalised theories of themselves without acknowledging or, worse, being aware of the history that they are drawing upon.

There is in all of this a tension between academia and industry that has been evident in the Service Design community, one that I witnessed (and still do) in the beginnings the 'new media' in the early 90s. Commercial service designer sometimes complained that the conference is already too academic – they want to see case studies the kind of show and tell inspirational talks that some conferences provide. The academic presentations are, for them, not grounded in enough practice. Others (academics) feel like there is a lack of rigour in the presentations, not grounded in enough theory and research. The way forward lies in both sides having some respect for the other rather than dismissing it. Service design does pull together many areas in which there has already been a lot of solid work and research done – it would be foolish to ignore it. And academia really does need to get to grips with the theory-practice gap if we're actually going to teach students anything useful.

So, I should probably have made that a blog post of my own, but conversations are good when they're in one place sometimes.