Whig and revisionist historians alike have argued that the efforts of Samuel Romilly and James Mackintosh to reform criminal law between 1808 and 1821 were easily thwarted by a resolute Tory ministry and an ambivalent public opinion. The cause of reform was in fact more powerful than either perspective allows. Urbane public opinion lamented England’s increasingly unique adherence to a wide-ranging death penalty and viewed its victims in more compassionate terms than ever before. Conservatives clung to William Paley’s arguments that a selectively enforced “Bloody Code” was both genuinely deterrent and preferable to either preventive policing or the wider use of secondary punishments. There were limits to the logic of the positions espoused by reformers and conservatives alike. By the 1820s, however, there was good reason to believe that the reform cause was already won in the House of Commons and that victory in the Lords was at least conceivable.

Recent historians usually see Home Secretary Robert Peel as a committed opponent of real criminal law reforms, content to hang large numbers of people. He did indeed enter office determined to diffuse reform momentum in parliament and succeeded in doing so, but only for a time. In fact, in pursuing the two reforms that William Paley deemed crucial to relinquishing the “Bloody Code” – preventive policing and more deterrent secondary punishments – Peel behaved like someone who believed his concessions might not hold back the tide of urbane public opinion for long. This was also apparent in his alterations to sentencing practices at assizes and his increasingly careful attention to execution levels in London. Even his consolidation measures were of more genuinely humane consequence than is usually recognized. Indeed, so adaptable to urbane opinion did Peel seem to his older, more determinedly conservative colleagues that by 1830 he inspired their distrust.

This chapter describes how the question of how animals perceive their world led to developments in discrimination training. These studies included ones that, for example, tested whether a dog, cat, or rat could learn to discriminate between two stimuli that differed only in color. Developments in the study of discrimination learning became increasingly theoretical. For example, one important issue had to do with the possible role of attention in discrimination learning. Rejection of this possibility by the highly influential behaviorist, Kenneth Spence, led to his important continuity theory. In turn, studies of phenomena such as transfer-along-a continuum and the overtraining-reversal-effect in the 1950s and 1960s by a series of researchers, including Stuart Sutherland and Nick Mackintosh in the UK, led to a revival of interest in selective attention in discrimination learning. The final section describes studies of stimulus generalization and behavioral contrast.