The articles in this Special Issue have been chosen to cover the rather wide range of topics that fall under the heading "Associative Learning." As such, they represent one strand of the work of Nick Mackintosh, who passed away in February 2015, with other aspects of his research, notably his work on individual differences and IQ, only touched on in passing. Nevertheless, even though they do not encompass the full range of Nick's interests, they still convey something of the sheer scope of his contribution to our subject, and the way in which he was able to take a particular approach to psychology and apply it to almost any subdomain of that discipline. The papers brought together in this volume are testament to the fact that this approach still commands our attention today and still has an important role in psychology at this time. An obituary to Nick is published in Biographical Memoirs of Fellows of the Royal Society (Pearce, 2018).The first article in this Special Issue is the Inaugural Mackintosh Lecture given at the Associative Learning Symposium held at Gregynog Hall, Wales, Easter 2016. This lecture series was established in honour of Nick's contribution to psychology and in particular to associative learning. In it, McLaren et al. (2019) make the case for associative learning in humans, an issue that Nick had worked on with several of the authors previously. Using paradigms ranging from Pavlovian conditioning in humans to task switching and sequence production, they show that there are more than propositional processes at work controlling behaviour and provide evidence for an associative component as well. Where this approach differs from more traditional dual-process theories is in emphasising the way that associative and rule-based processes are different facets of the same learning system. It is not that there are two systems operating in parallel; instead, the view is that there is one system that amounts to propositional processes constructed from an associative substrate. Such a system may typically seem propositional in nature, but can be persuaded to reveal its associative underpinnings.The second article, by Ahmed and Lovibond (2019), explores the peak shift effect, studied in both pigeons and humans by Sarah Wills and Nick Mackintosh (1998). Peak shift refers to the observation that, following training of two stimuli that differ along points on a dimension as a CS+ and CS−, conditioned responding is strongest not to the CS+ but to a stimulus further along the dimension from the CS+, in the opposite direction to the CS−. Lovibond and Ahmed show, in two shock conditioning experiments with human participants, that this effect can be modulated by verbalisable rules. In both experiments, different gradients were observed when participants were divided on the basis of the rules they reported using during the task (linear and similarity). The authors argue that their results imply the involvement of rule-based processes in the generalisation of conditioned fear along simple stimulus dimensions. Peak s...