According to standard procedure, building a classifier using machine learni
ng is a fully automated process that follows the preparation of training da
ta by a domain expert. In contrast, interactive machine learning engages us
ers in actually generating the classifier themselves. This offers a natural
way of integrating background knowledge into the modelling stage-as long a
s interactive tools can be designed that support efficient and effective co
mmunication. This paper shows that appropriate techniques can empower users
to create models that compete with classifiers built by state-of-the-art l
earning algorithms. It demonstrates that users-even users who are not domai
n experts-can often construct good classifiers, without any help from a lea
rning algorithm, using a simple two-dimensional visual interface. Experimen
ts on real data demonstrate that, not surprisingly, success hinges on the d
omain: if a few attributes can support good predictions, users generate acc
urate classifiers, whereas domains with many high-order attribute interacti
ons favour standard machine learning techniques. We also present an artific
ial example where domain knowledge allows an "expert user" to create a much
more accurate model than automatic learning algorithms. These results indi
cate that our system has the potential to produce highly accurate classifie
rs in the hands of a domain expert who has a strong interest in the domain
and therefore some insights into how to partition the data. Moreover, small
expert-defined models offer the additional advantage that they will genera
lly be more intelligible than those generated by automatic techniques. (C)
2001 Academic Press.