We know a lot about colours and how they affect people, but what do we know about shapes? When choosing icons or logos, how do the shapes in them affect their perception?
Does anyone know of any research that has been done into the psychology of everyday shapes or have any experience with how people perceive them?
Edit: I mean perceive here more in terms of emotionally than in terms of meaning. Something like, how a square make us feel as opposed to a circle or a triangle.
In a nutshell, the evidence suggests that users see rounded shapes as more 'friendly' than sharp shapes, and that sharp shapes, appearing slightly dangerous, garner more attention.
Some go further and suggest that, as a rule, you should give almost all your divs and content rounded edges except for call-to-action buttons, which attract more attention when squared.
Broad question, but the research is referred to as the field of Semiotics. There is a great deal of research and a good beginer intro is this site, as well as the Wikipedia link above. If you want general research you can search "semiotics" on Google Scholar but if you want specific research you'll have to ask a more specific question.
There is some research (try PsyBlog? can't remember source) that showed that people are more comfortable with rounder shapes and treat sharper shapes as more pointy/dangerous. It's in there with research showing, e.g., the contents of a heavier clipboard are treated as more serious than the contents of a lighter clipboard.
This is an interesting question.
It might be worth looking at the world of Gestalt Psychology and Optical Illusions, as optical illusions demonstrate situations where the brain is struggling to resolve incoming visual data. However I'm not aware that this would result in experienced or subconscious emotional reactions.
I also came this:
http://scienceblogs.com/cognitivedaily/2006/03/the_emotion_of_shapes.php
This answer is more from a practical, designers viewpoint.
As you are asking for emotional context I suggest to have a look at artists of constructivism, like Mondrian and Malewitsch, who explored this area of shapes, colors and its impact some times ago. But on a practical way rather, than scientific.
Which brings us to the synesthesia - an effect that lets you not even see glossy, slick buttons, but you know how it would feel if you press it physically. Or as Steve Jobs said: "You want to lick them".
There is a philosophy, close to psychology, called Phenomenology. Phenomenology has a quite good view of explaining effects like synesthesia. One of the most known books is Phenomenology of Perception from Maurice Merleau-Ponty. Its quite thick, but worth reading.
And there is Gestalt psychology - the basic patterns of visual recognition - coming from Experimental psychology in the early 1920ies.
Nowadays it would be just called neuroscience, but all its roots have been set 100 years ago. So you will get a solid understanding if you digg in the old books. Neuroscience has a focus on biological aspects, like how neurons react if you see a circle - but as a designer its doesnt matter. Its to detailed and no course of action for you.
I am currently doing my master's research in this area by having individual's model emotional labels. For example, they are given a set of interchangeable pieces and told to make an emotion. There is some base understanding of how people interpret the meaning of forms, but directly labeling them as emotions is very limited.
Meaning and emotion can be derived similarly, but are not actually the same. They are steps in forming understanding or interpreting an object. You are correct that some colors have innate messages as marketing research has shown that green often results in an uncontrollable increase in hunger. Blue creates a sense of calm, but dark blues will often make people sad over time similar to red increasing aggression or aggressive behavior.
I believe these both can be verified with primate research as well. This interpretation is built off our lived experiences, yes, as many foods are green. However, an evolutionary argument is that like primates we are attracted to green and yellow as they indicative of food sources. Evolutionary bright colors on insects or reptiles often indicate poison and can increase alertness of the observer. These two ideas may be opposite one another, but bright colors always draw attention.
Physically, our eyes are also able to distinguish yellow and red from white and black backgrounds, but have a difficult time viewing blues and greens.
Taking all of these ideas into consideration, evidence of both learned and innate reactions are apparent. Psychology in general is always a combination of both learned and innate abilities and through extensive research we are able to distinguish which side upon which we rely most heavily.
To answer your question directly, the assumption is so far that the meaning of 3D forms are representative of a combination of both Gestalt and Semiotics as stated previously, but I believe personification may also play a role.
In order to interpret an object or form as carrying an emotion we must personify them to some degree. Therefore, the semiotic understanding of a round 2D form often results in an interpretive meaning of connection may instead imbue a meaning of happiness when personification takes place.
However, I am still in the beginning stages of my research and am unsure if I've missed an area of research that goes into these emotional labels further. I will update once I learn more...
There is are two complementary ideas that support your question that have not been mentioned at this point - Constructal Theory, and the Golden Mean.
Constructal Theory proposes that systems work to distribute flaws in a way that minimizes them, and the Golden Mean is a common way of minimizing flaws (as it is also a common way of maximizing attraction).
Together, they form a strong argument for the evolutionary basis for the golden ratio.
Also, the golden ratio has been observed in gravity / parabolic functions, which supports an evolutionary basis for the importance of this "law" - and also supports the popularity of Angry Birds (the big eyes on the little bodies probably helps, too - another evolutionary trick to make babies more attractive).
