Animal cognition is a complex field. Until the 1960s, the term itself was considered an oxymoron, as animals were viewed as simple systems that merely responded to various stimuli in evolutionarily pre-programmed, invariant ways. As researchers began to observe animals more closely, both in the laboratory and in nature, however, they began to realize that this simplistic view failed to explain observed behavior patterns. Today, although there are as many definitions of animal cognition as there are researchers, most scientists agree that animal cognition, like its human analog, basically involves the processing of information: How a subject, within its species-specific perceptual system (auditory, visual, olfactory, gustatory, somatosensory) receives data from the world it inhabits (including data from other individuals), and, with its species-specific neurobiology, uses its brain to process and act on that information.

The field may be divided into various subtopics. For example, researchers who specialize in comparative psychology tend to examine a particular type of cognition, such as numerical competence, across various species, whereas researchers who specialize in cognitive ethology tend to look at how the evolutionary traits of a particular species allows it to interact in various ways with one or more aspects of its environment.

Most researchers engage in studies that overlap a number of different subtopics, because all studies involve various aspects of attention, categorization, memory, reasoning, and problem-solving, and sometimes answers to scientific questions can only be found by combining laboratory and field research. In all instances, scientists engage in carefully controlled experiments or well-designed observational studies.

Over the past several decades, the study of animal cognition has expanded to include an amazingly wide variety of species, from insects to our closest relatives, the nonhuman primates, and to incorporate a vast array of techniques.

Many advances in the field are, for example, owed to advances in technology: better ways to interact with and document nonhuman behavior in the field, noninvasive ways of examining brain processes in the laboratory.

Most importantly, the idea behind studying animal cognition is to determine the capacities of those creatures with whom we share our planet.