Some years ago, the Sexual Violence Centre in Cork carried out a survey on students' attitudes to sex.
Among its more shocking findings was the assumption by at least some teenage boys that they were "entitled" to sexual favours from girls they barely knew.
"There's this whole attitude from boys that they don't have to ask (for sex) - and the girls don't seem to know it has to be asked for," says Mary Crilly, who, as director of the Centre, regularly visits schools to discuss sexual violence and give presentations on the topic.
"The boys think that even if they know a girl for as little as an hour they're entitled to a sexual favour."
Boys can often feel they have a right to a woman's body and girls can feel they must comply with what the boy wants - but complying is not consent, warns Ellen O'Malley-Dunlop, chief executive of the Dublin Rape Crisis Centre, which along with Minister for Justice Frances Fitzgerald, has just launched its eye-catching #AskConsent campaign.
A strong billboard and internet initiative, it hammers home a simple message to teenagers: consent is a crucial part of any sexual activity.
The campaign, which has the support of the Union of Students of Ireland and the White Ribbon Campaign and rape crisis centres countrywide, will run for three weeks.
But how have we got to the stage where youths of 17 or 18, who may not as yet have even finished their secondary education, feel so comfortable demanding sexual favours like oral sex from their female peers?
"It comes from porn which is downloaded on smart phones and of which parents are not aware," says O'Malley- Dunlop bluntly.
"There's not enough sexual education there to counteract the messages young people are getting from the internet."
And in pornography - which is now easily accessible to any 10-year-old with a smartphone - Annie Hoey, deputy vice president of USI, observes that the mere issue of consent, either sought or given, is rare.
"This blurring of boundaries gives a really negative message," warns Hoey, who points to a 2013 survey carried out by USI amongst some 2,750 third level students.
It found that one-in-five women had experienced some form of unwanted sexual experience, with 11pc experiencing unwanted sexual contact.
Hence, USI's solid backing for the billboards and social media initiatives ramming home the consent message to both males and females: "You asked his/her name, you asked him/her out for drinks, you asked him/her back - you asked him/her if he/she wanted sex. Right? Sex without consent is rape."
It's not about demanding that self-conscious teenagers boldly ask one another if they want sex, says O'Malley-Dunlop - it's about creating a strong awareness of the absolute necessity for consent.
"The idea of the campaign is awareness-raising; to get people talking about consent in the context of a sexual relationship.
"We want to get young people talking about it, because year-on-year we see an escalation in the numbers of young people who are victims of sexual violence.
"In July and August this year alone we accompanied 68 victims of sexual assault to the Sexual Assault Treatment Unit in the Rotunda," she says.
A 2014 study of university students commissioned by the Rape Crisis Network Ireland and carried out by NUI Galway found that "acquiescence" to the other person's "advances" was taken to indicate "tacit consent."
The rule of thumb was for the male to progress the degree of physical intimacy until the female "clearly" indicated she wished him to stop. However, researchers noted, there was "pressure perceived by females to go along or acquiesce to the partner's intentions due to self-consciousness or a desire not to be seen as frigid."
In this context, the campaign, with its strongly worded message on the necessity for clearly expressed consent, appears to be pushing an open door - there's "a huge appetite" among young people for a debate on the whole area of sexuality and sexual relationships, O Malley-Dunlop says.
Opening up such a debate is the objective of the colourful campaign, which is funded by COSC, the national office for the Prevention of Domestic, Sexual and Gender-based violence.
"We want to get young people talking about this and not taking it for granted that someone wants to have sex because he or she responds in a particular way," O Malley-Dunlop explains.
"We want young people to notice if the person with whom they are engaged in sexual activity is not responding with enthusiasm.
"Check it out. If they're not glad to continue, stop.
"If someone is asleep or drunk or comatose, notice it and don't even start," she said, adding that Rape Crisis Centre personnel "have accompanied people to court where a partner has had sex with them while they are asleep or drunk and simply not able to give consent.
"As well as the billboards, we have social media platforms with a variety of different initiatives highlighting the importance of consent. These are educational and this is an education campaign," she says, adding that many people don't appreciate that the law is very black and white on the subject.
"If you've had sex with a person without their consent it is rape."
The problem is, she points out, how do you actually prove it is consensual?
"If we had an objective definition of consent in the law it would be easier to prove whether or not consent was given."
"There's a huge amount of pressure on young people to be sexually active," warns Hoey, who believes a major factor in all of this is the glaring lack of an effectively holistic sex programme of education at second-level which would drive home both the need for consent - and a person's right to say 'no.'
Such a programme is needed, she says, "to counteract the negative messages streaming through from the porn industry."
However, she says, instead, the sex education at second-level seems to focus primarily on the prevention of sexually transmitted disease and pregnancy.
"We need to talk about sex in a much more holistic manner," she says, adding that such a programme would teach young people how to say an affirmative 'yes', and that it is completely "okay" to say no.
"I hope this campaign will drive the message home that it is a need to check in and see if the other person wants to engage in sexual activity.
"Let's start talking about when we want to have it and when we don't want to have it and get rid of the culture of silence.
"We need to start teaching young people that you never assume the other person's consent."
Crilly, who has worked in the area of sexual violence for more than 30 years believes that there's another factor at play in this mix - one which lets boys 'off the hook' as regards their behaviour while loading all the responsibility for behaving appropriately on the shoulders of girls.
It's to do with attitudes in Irish society and the way we parent our kids, she says:
"There is a double standard in which boys are 'only lads' and are 'entitled' to try anything and it's a girl's responsibility not to do it.
"As a general rule in society we don't say to boys that certain behaviours will not be tolerated - it's a case of 'boys will be boys and sure they're only trying it on.'
"That is what boys are being taught - to be a 'free spirit' and 'try it on' and this contributes to their feeling of entitlement."
However, says Crilly, a growing awareness of this double standard, and of the existence of a 'rape culture' in which boys are egged on and girls are blamed, is grounds for some optimism:
"There is a growing awareness of this and of the fact that as a society we need to stop this toleration of rape and sexual assault."
For more information visit drcc.ie. The National 24-hour helpline for victims of sexual violence is 1800 7788