Sociology. Although the origins of sociology can be traced back to the nineteenth century with the work of pioneers such as Max Weber, Emile Durkheim and Auguste Comte, it has been one of the more recent of the social sciences to establish itself as a discipline of university study within the Anglo-American tradition. Sociology could be defined very broadly as 'the study of society'; for example, researching into structures, change, and conflict within society. However, as with psychology, there are many disagreements about what should be the appropriate subject matter, aims, and methodology of sociology. Sociologists such as Marx and Parsons focus on social structures and institutions (e.g. capitalism, or the nuclear family); other sociologists such as Weber study social interactions on a much smaller scale (e.g. how individuals and groups develop social relationships). A third approach takes as its focus the study of collective representations: looking at how many of the ways in which we make sense of the world are constructed at societal levels (e.g. representations of political parties such as Labour and the Conservatives). Like psychology, modern sociology has given birth to a number of closely-related fields, such as cultural studies.\nSome branches of psychology have been heavily influenced by sociology, for example the broad approach to studying social psychology called 'sociological social psychology' (SSP). Instead of tackling social psychology by establishing the principles governing the individual, and then seeing how these are modified in a social setting, SSP approaches make the social central and view it as inseparable from individual processes. Instead of seeing the social context as simply another 'variable', they ask questions such as 'in a particular social setting, how do the social and cultural practices actually act to construct the individual, as he or she develops from childhood?'. 
Introspection. Essentially, this method involves attempting to examine one's own psychological experiences (i.e. the contents and processes of the conscious mind) and report back what is found. This was one of the main methods of the early pioneers of psychology, such as William James, much of whose influential writings of psychology come from relatively informal and unstructured introspectionist reports of his own experiences. In a much more structured and formal way, Wilhelm Wundt established a psychological laboratory in Germany, where he tried to break down sensory experience into its component parts based on introspectionist data from a number of participants. In terms of the history of psychology, Wundt's failure to achieve inter-observer reliability with these types of data led to the rise of Behaviourism with researchers such as Watson rejecting mental data of all kinds as 'unscientific', and limiting psychology to the study of externally-observable behaviour. Since then, introspectionist data have more recently again found a place in psychology (though it's fair to say that introspection is still shunned by many psychological perspectives). In cognitive psychology, although the main focus is usually on experimental data, some cognitive psychologists have got people to 'talk through' their experiences when engaged in cognitive activities such as problem solving, with the resulting 'verbal protocols' seen as a useful complement to experimental data. Introspectionist reports of individual experience are an important part of humanistic and transpersonal psychology (e.g. in studying altered states of consciousness). These type of data are particularly important in transpersonal psychology, partly as a result of the way this perspective has been influenced by eastern philosophies/psychologies such as Buddhism, which have always used introspection as their primary method.