Diners who only watched as Nigella Lawson was assaulted were probably influenced by the "bystander effect" - something an anti-domestic violence group says is at play daily in New Zealand.
Charles Saatchi has accepted a police caution for assault after the emergence of pictures showing him repeatedly grabbing Lawson, his wife, by the throat at a restaurant.
Witnesses later described the incident as shocking, but neither fellow diners nor waiters stepped in or took other action.
University of Auckland psychology lecturer Dr Danny Osborne said media reports made it clear numerous witnesses recognised the incident as an assault, or emergency, yet none then made the next step to help.
This could be explained by the "bystander effect", which means the more people present in an emergency, the more likely offers of help will be inhibited.
Arguments between couples and any ambiguity on what was happening increased the likelihood no action would be taken.
"You are going to see a lot of cons popping up in people's minds ... if you intervene it's possible the person being assaulted might take offence and wind up getting upset with you."
Jane Drumm, head of anti-domestic violence agency Safer Homes in New Zealand Everyday (Shine), said her organisation daily saw the consequences of witnesses not offering help or taking action.
"We encounter situations where people look away, they're embarrassed, they don't want to get involved, they avoid it.
"And that stuff is the kind of stuff that allows this to keep going.
"Because ultimately it's not going to be police, or organisations like ours, that stop this. It is going to be next-door neighbours, friends, family, workmates."
Those who witnessed an incident like that which involved Lawson could ask others around them to approach the table together, or voice their concern without getting too close to the offender.
"A simple thing, say to Nigella or whoever, are you all right? Do you want to move away? Or, to him, we don't like what you're doing."
The fact Saatchi put his hands on his wife's throat in public was a high-risk indicator, Ms Drumm said, and pointed to worse abuse in private.
She said those calling for Lawson, a celebrity chef, to become an anti-domestic violence campaigner, including Australian radio presenter Dee Dee Dunleavy, were wrong.
"There should be no pressure on her to do anything - to stay with him, to leave him, to take him to court for every cent he's got, to be a postergirl against domestic violence.
"The pressure should be on him."
Where to get help
*Women's Refuge - 0800 REFUGE or 0800 733 843
*It's Not OK helpline - 0800 456 450, www.areyouok.org.nz
*Shine - www.2shine.org.nz, 09 815 4601 (Auckland), 0508 744 633 (Nationwide)
*Victim Support - 0800 842 846
*If you are in immediate danger or can see someone who is, call 111 for Police