Posture doesn’t just reflect our emotional states; it can also cause them. In a study published in Health Psychology earlier this year, Shwetha Nair and her colleagues assigned non-depressed participants to sit in an upright or slouched posture and then had them answer a mock job-interview question, a well-established experimental stress inducer, followed by a series of questionnaires. Compared with upright sitters, the slouchers reported significantly lower self-esteem and mood, and much greater fear. Posture affected even the contents of their interview answers: Linguistic analyses revealed that slouchers were much more negative in what they had to say. The researchers concluded, “Sitting upright may be a simple behavioral strategy to help build resilience to stress.”

Slouching can also affect our memory: In a study published last year in Clinical Psychology and Psychotherapy of people with clinical depression, participants were randomly assigned to sit in either a slouched or an upright position and then presented with a list of positive and negative words. When they were later asked to recall those words, the slouchers showed a negative recall bias (remembering the bad stuff more than the good stuff), while those who sat upright showed no such bias. And in a 2009 study of Japanese schoolchildren, those who were trained to sit with upright posture were more productive than their classmates in writing assignments.

How else might iHunching influence our feelings and behaviors? My colleague Maarten W. Bos and I have done preliminary research on this. We randomly assigned participants to interact for five minutes with one of four electronic devices that varied in size: a smartphone, a tablet, a laptop and a desktop computer. We then looked at how long subjects would wait to ask the experimenter whether they could leave, after the study had clearly concluded. We found that the size of the device significantly affected whether subjects felt comfortable seeking out the experimenter, suggesting that the slouchy, collapsed position we take when using our phones actually makes us less assertive — less likely to stand up for ourselves when the situation calls for it.

In fact, there appears to be a linear relationship between the size of your device and the extent to which it affects you: the smaller the device, the more you must contract your body to use it, and the more shrunken and inward your posture, the more submissive you are likely to become.

Ironically, while many of us spend hours every day using small mobile devices to increase our productivity and efficiency, interacting with these objects, even for short periods of time, might do just the opposite, reducing our assertiveness and undermining our productivity.