WHEN you fill in a form in this country, there are usually only two tick-boxes for gender: male or female.

Even when someone is unhappy with their gender, we expect that they simply want to be the other one. If you're trans, you must be a man who always felt like he should have been born a woman, or vice versa.

But gender is becoming a more fluid concept. There are now 73 categories of gender and sexuality to self-define as on Facebook and north of the Border, activists are campaigning to have a third gender recognised in Scottish law, so that all forms would need to provide a tick-box for a third category, a neither of the above.

I first became interested in the trans community when I met some young trans people at a workshop, where I encountered none of the stereotypes often presented in the media. Some described themselves as "non-binary" (rejecting the idea that there are only two clear-cut genders) and asking to be called by the gender-neutral pronoun "they", rather than "he" or "she".

I left the workshop wanting to know more about these people: not just about their personal lives, but about what their experiences told us about how gender is created in this world, and the possibilities of living outside those notions. What compels them? What do they think causes their gender dysphoria (unease with one's body)? We live in an age in which it seems there should be greater freedom to act outside the box, in which gender should be irrelevant, yet where the pressures to conform to ideals and notions of femininity and masculinity, particularly in childhood, seem as intense as ever.

The trans world is changing. Some of the people I interviewed for this piece continue to identify strongly with ideas of male or female. Others are rejecting what they call the "gender binary", and shunning the rules that the previous generations have held about transitioning. What does the rise of the "non binary" say about gender in society today?

Nathan Gale

Trainee solicitor, 30

When you're transitioning from female to male, as I did in my early 20s, you're expected to believe something like: "I've always known that I was supposed to be a boy." You're told to dress in a masculine way. There were bits of me I had to leave behind in order to be a guy - nail polish, certain clothes. At the time, that felt like the trade-off I had to make. But after a while I started to feel uncomfortable.

Once I realised that gender was largely socially constructed, I started allowing some of those things back in. I thought: "You know what, I really enjoyed painting my nails. Why did I stop doing that?"

The term "male" or "man" no longer felt like it suited me. It doesn't explain the journey I've been on. It denies part of my identity. So gradually I started to dress and act who I felt like. I came across this term "non-binary" and thought - that fits how I feel. I've got masculine and feminine traits and neither man nor woman describes who I am.

As a kid, I knew something wasn't right, but couldn't articulate it. I felt uncomfortable. I didn't fit in anywhere, with boys or girls. Aged 15, I fell in love with my best friend, a girl. We got together and I thought: "Oh well, I'm a lesbian. That explains everything."' But I felt wrong in my body and soon I realised I felt much more masculine. I was horrified by puberty. After meeting some trans people at an LGBT youth group, I realised it was possible to transition and by aged 17, I knew that was what I wanted.

I came out on my 20th birthday, during an argument with my mum. She asked: "Why are you so angry and aggressive all the time?" I think it was then that I said that I felt wrong. It was difficult for my mum, who's a real feminist. She felt she'd lost her daughter. But we've worked through it and I couldn't have asked my family to be more supportive.

Pretty quickly after I came out I started taking hormones. I had chest surgery three years later, which was incredible, but afterwards I had a crash. Back then, a lot of people in the trans community denied that you should have mixed feelings about it. When you're transitioning often it's like you've got to be this kind of male or this kind of female. It's really difficult for people who don't feel really masculine or really feminine.

Having gone through the process of getting legal recognition as male, I am a civil partnership with a man. I describe my sexuality as queer and I'm campaigning for recognition of a third gender in Scottish law. I help run a group called Non Binary Scotland. More and more people are identifying as non binary and fewer trans young people are identifying as male or female. Gender is going out the window. They don't feel the need to choose.

A person who can't be neatly gendered scares people. Sometimes I just resign to presenting myself as male. I have come to a place where I think just because that person is gendering me as male doesn't mean that's my gender. It's just a comment on how they choose to read me. I can still be me and authentic.

It's so hard to pick it apart how much of my feelings around gender and my body were because of the social construct and pressures around gender. But I did have huge dysphoria around my body. That intense discomfort with my body is so acute that I can't believe that it's not within me. Of course, if society didn't gender particular body parts it's possible I might have felt differently, but you can't know. So, given that, I think we just need to focus on what it is that makes the person most comfortable.

Eilidh Nicolson

Artist, 26

When I was a four-year-old boy I thought: "I want to grow up to be a woman." I felt I was a blank slate and could do that. I thought all the women I know have got long hair and all the men have got short hair: I'll grow my hair long and be a woman.

When I hit puberty I started having more vivid fantasies about being a woman. I knew it wasn't normal; that if I told any of the boys in my class I'd get ridiculed.

I did fancy girls. But I was scared that I'd date them, marry them and then come out as trans. I didn't want to break a girl's heart by coming out to her later in life.

After leaving school I buried myself in education, studying computing science. I failed after three years and took a year off and taught myself to draw. I started drawing little trans people. "I like these people," I thought. "Does it feel different to be them?"

By the end of 2011, I got a temp job. One day, I found myself breaking down in the supply closet, crying about how unhappy I was with my life. It felt a lot of self-loathing about the way I looked. On that Friday night I wrote my mum a letter and on the Saturday I pushed it into her hands and ran out of the house to go to the dentist. The main line in it was: "I love transsexuals and want to be one."

I came home from the dentist's feeling really anxious. I rang the doorbell and when my mum let me in, I thought: "Thank God, she's not kicking me out." I had a great sense of relief: "I'm accepted." So on January 1, 2012 I put on a dress, wore it to see in the bells and never went back.

When I first came out, I thought I should save up for genital surgery. My mum asked why I wanted the surgery, and I realised I didn't want it. I'm scared of it, and I feel: what does it matter? If I'm walking down the street, you perceive me as a woman. You'll never know what's between my legs.

I've been on oestrogen pills and testosterone-blockers for two years; my boobs have gone up to B cups and they're still growing. I don't want a boob job, but most women do because the pressure on wome to have big boobs is even greater if you're trans.

Testosterone really blocks your emotions. It's a stereotype to say men aren't very good at expressing their emotions but it's true. I was an emotional kid who cried a lot. When I went through puberty I stopped that. I found it hard to express myself other than through anger. Then I started hormones and it's like I'm a kid again, crying at everything.

I'm not in a relationship. I didn't get any sexual experience in my teenage years so don't know how to do it. Hormones make you go through puberty again. It's nuts, having a second puberty. I'm also scared because what kind of person accepts me? A straight woman wouldn't, but a lesbian woman would be like: "What's that between your legs? When are you getting rid of that?" They probably wouldn't like it when I tell them "never".

My mum and I are really close now. I've even got closer to my dad. I am lucky in that I can live with them and they'll take care of me. I can transition at my own pace. I don't have to rely on sex work to get by. I'm trying to get a job but it's difficult. When I was growing up everyone would say you're smart, you're desirable you'll get a job no problem. Now I'm being told, you're not going to get a job because you're transgender. But my skills are the same. I want to be an artist. That's the dream.

I like being trans. I don't see it as a defect I need to correct. The corniest thing I've ever said is it's less about transitioning from man to woman, and more about transitioning from unhappy to happy.

Maki Yamazaki, musician and artist, 30

I identify as non-binary. I prefer the pronoun "they" to "he" or "she". I'm fine if someone calls me "she", but I'm very averse to "he". If I were to pick a gender identity it would be "not male".

From a very young age I knew I didn't fit in with typical views of gender. As a child, growing up a boy, I was bullied a lot for being feminine, for not being interested in fighting, for crossing my legs, body language, the way I talked, the company I kept. I liked hanging out with girls. I found it very difficult to relate to most boys. I didn't really have any positive male role models.

I remember feeling that I had to be a certain way. People would say: "Be a man." Or, "Are you a boy or a girl?" You weren't allowed to be sensitive.

My teens were the hardest time. As a teenager you're discovering your identity. People's bodies are changing, and things like school bullying get a lot worse. At that time I tried so hard to suppress anything that might make me a target of abuse. But some things are hard to hide, things you aren't even aware of: your mannerisms, the way you react to situations.

Puberty was horrible. I was very at odds with my body. My transition came out of how I felt about my physical body. I knew I did not identify as male. My transition has allowed me to explore more feminine things and femaleness. But it really was the springboard for me realising that I was neither. It has been a transition from male to me.

The idea that gender presentation and one's own body might not be identical, that for instance, a male body might not be male gendered, is unfathomable to some. But our bodies are not necessarily an expression of our gender.

I've experienced transphobia. I was knife-attacked by someone outside a nightclub in my hometown. Some random stranger didn't like the way I looked. But I think even if I hadn't been trans, just a very feminine boy, the problem would have still kicked off.

Most people I know would rather be seen as themselves than their gender. I'm not keen on the tags. I don't necessarily want people to know what's in my trousers. I only share that information with people who it's relevant to.

Robin Duval

Community engagement manager, 30

I had chest surgery [double mastectomy to create a male-contoured chest] a couple of months ago and I'm feeling so liberated. Now when I look in the mirror my body reflects how I see myself. Before, when I looked down at myself it didn't look like me.

It's taken a while to get to the point of being confident about being non-binary. When I was about 14 and a girl at a girls' school something didn't feel right. I felt out of place, so I just hung out by myself. I thought: "I'm going to ride my bike and listen to music. I don't really get what's going on here." But at 16 I went to a mixed college and made some male friends. They just treated me like me, but I definitely didn't fit. At that time I thought I was asexual. I think people interpreted me as a lesbian and some friends tried to support me to come out. But I wasn't sure I feel like that.

I had quite a delayed puberty. I had an eating disorder which I think was partly related to not wanting to go through puberty. Beginning to identify as non-binary in my mid-20s helped me overcome my eating disorder. However, as I put on weight I began to go through female puberty which made me feel really disassociated from my body.

My social transition began in 2007 when I changed my name to Robin to reflect my non-binary identity. I had a few friends who identified as transmen and had begun to take hormones. As I saw the changes they experienced I realised I also wanted to take hormones. At this time I thought that in order to access hormones you had to identify as a transman. This had a big affect on how I told my story and how I came out to people. The more I tried to make myself fit, the more I felt I didn't fit into the category of man or woman.

Chest surgery is quite difficult for non-binary people to access through the NHS so I had to pay for it privately. But it should be accessible on the NHS - as not having it done, particularly if you are binding your chest, can adversely affect your health. When the bandages off and I saw my chest for the first time, I shook the surgeon's hand and thanked him. I had been binding for years and experienced quite a lot of social anxiety and disassociation from my body which contributed to some periods of quite severe depression.

I've got a boyfriend and he's pretty awesome with things. With my family, acceptance is an ongoing process. I don't find it easy to talk to them about it, but my sister is quite good. She calls me "bris".

I'm campaigning for the recognition of a third gender in Scottish law. If you're filling in a form and have to choose between male and female you're either made to feel like you don't fit or like you're trying to fit yourself to something which doesn't feel true to you. If there was an acceptable legal category for people who aren't exclusively male or female, it would make navigating the world a lot easier for me.

Interviews by Vicky Allan