Smaller than 50 places
More than ten years ago, a team of Norwegian researchers measured the quality of life in all 32 closed prisons in Norway. They found that the experienced quality of life was significantly higher in prisons with a capacity of less than 50 places (Johnsen, Granheim & Helgesen, 2011; Johnsen & Granheim, 2012). In these small prisons, incarcerated people experienced their relationships with staff, their general treatment and their well-being more positively than those in larger prisons. Interestingly, these positive experiences were also found for frontline staff members, both in their interactions with incarcerated people and with their senior management. These findings are in line with other international research and suggest that prison facilities with a capacity of less than 50 perform better in areas that really matter to the people involved.
Yet, however interesting these findings are, they only tell part of the story. It would be too simple to conclude that all prisons with a capacity of less than 50 places perform better than larger prisons. One important observation is that almost all small-scale prisons in this Norwegian research had a capacity that was much lower than 50, with an average of around 25 places per prison. This observation was also made by architects who visited small-scale prison facilities for various research projects, like Sabrina Puddu (University of Cambridge & University of the Arts London) and Matt Dwyer (Local time). Even though they visited very different facilities in different countries and for different projects, they received similar answers to the question about the ideal number of people per facility: between 8 and 24-25.
The meaning of numbers
So how about a capacity of 7, 26 or 49? Does this number really matter? It does matter more than one would think at first glance. As confirmed by the Norwegian research, the benefits of small scale facilities are related to the quality of the relationships between incarcerated people, first-line staff members and management, and more specifically to the nature of communication, feeling of involvement, sense of fairness and respect. Given the importance of relationships or social interactions, the scale should not be measured by the number of people, but by the number of individual relationships or social interactions between these people. For example, in a group of 4 individuals (person A, B, C, D), there are six possible interactions between them (A with B, A with C, A with D, B with C, B with D, C with D). With each additional person, this number of relationships increases exponentially. In a group of 24 people, there are 276 possible individual relationships and in a group of 30 people this becomes 435. When considering a prison or detention house with a capacity for 24 or 30 incarcerated people, we are rather talking about groups of 48 or 60 people (with a 1:1 staff-resident ratio), and the number of relationships between them will increase accordingly. When looking at these numbers, it is much easier to understand why it becomes challenging or impossible to really know each other individually in a facility with more than 24 or 25 incarcerated people.
For the same reasons, there is also a minimum number of people needed to create the minimum number of interactions necessary for a healthy group dynamic. When Matt Dwyer visited facilities for young people, it became clear to him that this minimum is 8. The desired group dynamics were unlikely to emerge in groups with less than 8 young people. Also Sabrina Puddu was told that the minimum is 8, since a smaller group does not allow for enough variety in social interactions, which can then easily result in toxic relationships and conflicts. Similar experiences with tense social climates were heard in Norway, in the context of the very small local prisons that housed only 4 or 5 people (but have been closed down a long time ago).
 This insight was explained to me by Matt Dwyer.