Your hand is not a perceptual ruler

Visual perception has a problem; it doesn't come with a ruler. 

Visual information is angular, and the main consequence of this is that the apparent size of something varies with how far away it is. This means you can't tell how big something actually is without more information. For example, the Sun and the Moon are radically different actual sizes, but because of the huge difference in how far away they are, they are almost exactly the same angular size; this is why solar eclipses work. (Iain Banks suggested in 'Transition' that solar eclipses on Earth would be a great time to look for aliens among us, because it's a staggering coincidence that they work out and they would make for great tourism :) 

This lack of absolute size information is a problem because we need to know how big things actually are in order to interact with them. When I reach to grasp my coffee cup, I need to open my hand up enough so that I don't hit it and knock it over. Now, I can actually do this; as my reach unfolds over time, my hand opens to a maximum aperture that's wide enough to go round the object I'm reaching for (e.g. Mon-Williams & Bingham, 2011). The system therefore does have access to some additional information it can use to convert the angular size to a metric size; this process is called calibration and people who study calibration are interested in what that extra information is.

The ecological approach to calibration (see anything on the topic by Geoff Bingham) doesn't treat this as a process of 'detect angular size, detect distance, combine and scale', of course. Calibration uses some information to tune up the perception of other information so that the latter is detected in the calibrated unit. The unit chosen will be task specific because calibration needs information and tasks only offer information about themselves. A commonly discussed unit (used for scaling the perception of long distances) is eye height, because there is information in the optic array for it and it provides a fairly functional ruler for measuring distances out beyond reach space. 

Linkenauger et al (2014) take a slightly different approach. They suggest that what the system needs is something it carries with it and that remains constant (not just constantly specified, as with eye height). They present some evidence that the dominant hand is perceived to be a fairly constant length when magnified, and suggest that this length is stored and used by the system to calibrate size perception in reach space. There are, let's say, a few problems with this paper. 

Perceiving causes; why knowledge doesn't trump perception

You're an organism, wandering round the world. Some stuff happens; then, other stuff happens. How do we know whether the first stuff caused the second stuff to happen, or whether it's all just one damn thing after another? A new study in Psychological Science (Bechlivanidis & Lagnado, 2013) investigates whether what we know can affect what we perceive, and claims to show that perception can get overridden. This caught my eye because it sounds like the kind of result that will be a problem for our embodied cognition (Wilson & Golonka, 2013), but thinking through the experiment using the tools of dynamics and event perception shows that this result is not going to cause us much concern - it just isn't studying what it says it's studying.

Psychological Science...meet me at camera 3

Psychological Science, I think we need to talk. I was reading this farewell from your outgoing editor, and it would all be nice enough if I hadn't also just read your latest offering to the altar of 'embodied' cognition. Frankly, it made me wonder whether you actually read all the things you publish.

Robert Kail, the outgoing editor, had this to say about the ideal Psychological Science paper:

...the ideal Psychological Science manuscript is difficult to define, but easily recognized — the topic is fundamental to the field, the design is elegant, and the findings are breathtaking.

There are a few problems here; 'breathtaking' results have the tendency to be wrong, for example, and while I'm all for elegant design, sometimes, to make a breath taking claim, you need to run those 4 control conditions. But my main problem is less with these criteria and more with the papers that apparently meet them.