Sunday, April 4, 2010

Reward And Interest

Justin Wehr has a cool post summarizing an article by Paul Silvia about what makes certain things interesting.  Silvia argues that interesting things are new / complex / unexpected and, crucially, comprehensible. About textbooks, he writes that:
[T]he largest predictors of a text's interestingness are (a) a cluster of novelty–complexity variables (the material's novelty, vividness, complexity, and surprisingness) and (b) a cluster of comprehension variables (coherence, concreteness, and ease of processing). Intuition tells us that we can make writing interesting by "spicing it up"; research reminds us that clarity, structure, and coherence enhance a reader's interest, too.
On the personality traits that predict high amounts of interest as opposed to happiness:
Interest connects to openness to experience, a broad trait associated with curiosity, unconventionality, and creativity. Happiness, in contrast, connects to extraversion, a broad trait associated with positive emotions and gregariousness.
Surprisingly, neither Silvia's article nor Wehr's summary mentions how the expected reward of an activity correlates with its interestingness. Surely we become more interested in things if we expect that our interest could be paid off in a big paycheck or the opportunity to publish a paper in a prestigious journal. With respect to the latter, we often immediately become less interested in something once we learn that it has already been published. This phenomenon that cannot be explained without resorting to expected reward!

Other papers have not overlooked this component of interest. For example, in Jianzhong Xu's article on predicting student's interest in homework, he notes that,
[Some] theorists argue that significant others (e.g., parents and teachers) may play an important role in enhancing interest, through external support and continuous feedback... [T]he variation in homework interest was positively associated with affective attitude toward homework, motivational orientation toward homework, student initiative in monitoring homework motivation, teacher feedback, and self-reported grade.
The Pearson correlation he found between interest and self-reported grades was not huge (r = 0.12), but still highly significant at p < 0.01. Moreover, the test just asked for overall school grades (either mostly A's, B's, or C's...) and overall interest. I'd expect that if you looked at interest on an individual assignment, there would be a much higher correlation with the grade on that particular assignment.

At one point Wehr quotes Lennart Sjöberg, who is confused by the inability of interest theory to explain his daughter's hobbies:
My 10-year-old granddaughter is extremely interested in horses and riding, like so many girls of her age. Some of that interest possibly can be explained by collative variables and the activity of riding a horse, taking care of it, and so on, but there also seems to be a question of sheer fascination with horses per se, quite regardless of any activity having to do with horses. We may be hardwired to develop a lust for certain types of objects and activities. Genetic determination of part of the interest variance is a very real possibility.
I highly doubt that there is a polymorphism that predicts liking of horses by young girls! Instead, I'd bet that his daughter gets reinforcement from liking something that her friends and cultural role models like, which makes her much more interested in horses qua horses.

However, if Sjöberg is referring to the genetic components of being interested in broad topics in general, he's surely right. Openness to experience is highly heritable, with estimates of the percentage variance explained by genetics ranging from 45 - 61% (here via here), 57% (here), to ~ 40 - 50% (here).

One specific polymorphism that is associated with openness to experience is the number of repeat alleles in the gene coding for the dopamine receptor D4. Comings et al's chart shows the U-shaped dependence of openness to experience on this one polymorphism, with higher repeat allele numbers to the right, and higher scores for openness to experience up:
Comings et al, 1999, PubMed ID 10402503
One study describes "a possible molecular link between [the] dopamine DRD4 receptor, music and autism, possibly via mechanisms involving the reward system and the appraisal of emotions."

Once I started blogging, I started becoming interested in lots more topics. This can be easily explained by the link between reward and interest. Once you are a blogger, everything you read has the potential to be blog-worthy. You are rewarded for finding good stuff that your readers enjoy by e-mails, comments, and silent, knowing nods of approval. This drives you to be interested more by the things that you read. There's nothing particularly magical about it.

It's no wonder AI researchers like Shane Legg study the neuroscience of the reward system. It's probably our most powerful set of circuits. And when explaining things like interestingness, it's hard to ignore.