Lord Blunkett made an interesting point on Friday's Today programme (2'18" in):

Nobody below their mid-50s will remember the early 1980s...The problem for the group who think it would be possible to create a new [centre] party is that they have forgotten or didn't know about what happened to the SDP [that it fragmented the opposition and so gave the Tories a huge majority].

What he's driving at here is that our beliefs are shaped not merely by facts but by the direct memories of our formative years. If you were politically aware in in your teens and early 20s in the mid-80s, you'll have vivid memories of how the SDP did indeed weaken Labour*, and how early hopes for the party were dashed. Amongst 50-somethings, these memories create a jaundiced view of new centre parties - a view perhaps not shared by those younger than us.

This reminds me of two papers by Ulrike Malmendier and Stefan Nagel (pdf) and by Henrik Cronqvist and colleagues. They show that people who spent their formative years in recessions hold fewer shares, but more value stocks, even years later than people shaped by good economic times. Lord Blunkett is saying that their point generalizes to political attitudes. I suspect he's right. Here are some other examples:

- Young activists such as Ash Sarker and Aaron Bastani boast of being communists. People of my generation with similar opinions, however, would avoid that word as for us it is tainted by association with Stalinism. Those whose formative years were spent after the collapse of Communism have no such inhibitions, however.

- People in their 20s have spent their formative years living with the financial crisis and its aftermath. They are therefore more likely to be sceptical of capitalism than those in their 30s and 40s, whose formative years were spent in times of stable growth. It should, therefore, be no surprise that they are disproportionately supportive of Corbyn - and that those of us shaped by the recession of the early 80s should be sympathetic to them.

- Those of us who remember the strikes of the 70s and 80s know that class struggle matters. For those slightly younger than us, however, class is less salient - though even younger people are relearning its importance.

- For people whose formative years include 2003, the Iraq war made a big impression; it is these, I sense, who are most hostile to Blair. For the rest of us, the war was just another policy error.

- My ideas were disproportionately shaped by the inflation and mass unemployment of the 70s and 80s. These taught me that economics matters; it's not merely a way for second-rate mathematicians to fool themselves that they are clever. People who enjoyed economic stability in their formative years, however, might think economics less important.

The psychology here is simple. There is such as a thing as an impressionable age - in this context, our teens and early 20s. I, for example, have vivid memories of most of what happened between around 1976 and 1989, but everything before then is what I've only read or heard about, and everything since is a bit of a blur, mostly of minor significance.

Hume was more or less right. We have impressions - things which enter our mind with "most force and violence" - and ideas, which are "faint images". Our experiences in our formative years are impressions; everything else is an idea. This, I suspect, lies behind at least some of the generational divide in politics. And its partisans are insufficiently aware of it.

* I suspect that for some centrists today, the risk of letting the Tories win is one they are happy to take.