The terms ability, cognitive ability, achievement, aptitude, aptitude-achievement are tossed around in contemporary psychological and educational assessment circles, often without a clear understanding of the similarities and differences between and among the terms. For example, what does an “aptitude-achievement” discrepancy, in the context of contemporary models of SLD identification (see Flanagan & Fiorrello, 2010), mean? Where are the aptitudes in the CHC model? It is argued here that it is critical that intelligence assessment professionals and researchers begin to use agreed upon terms to avoid confusion and to enhance collaboration and to facilitate research synthesis. In this spirit, the figure below illustrates the conceptual distinction between abilities, cognitive abilities, achievement abilities and aptitudes. These conceptual distinctions are drawn primarily from Carroll (1993)and the work of Snow and colleagues (Corono et al., 2001). [Click on image to enlarge]
As reflected in the figure, all constructs in the CHC model are abilities. As per Carroll (1991), “as used to describe an attribute of individuals, ability refers to the possible variations over individuals in the liminal levels of task difficulty (or in derived measurements based on such luminal levels) at which, on any given occasion in which all conditions appear favorable, individuals perform successfully on a defined class of tasks” (p. 8, italics in original). In more simple language,“every ability is defined in terms of some kind of performance, or potential for performance (p. 4).” The overarching domain of abilities includes cognitive and achievement abilities as well as aptitudes (see figure). Cognitive abilities are abilities on tasks “in which correct or appropriate processing of mental information is critical to successful performance” (p. 10; italics in original). The key component to the operational definition of cognitive abilities is the processing of mental information (Carroll, 1993). Achievement abilities “refers to the degree of learning in some procedure intended to produce learning, such as an informal or informal course of instruction, or a period of self study of a topic, or practice of a skill” (p. 17). As reflected in the above figure, the CHC domains of Grw and Gq are consistent with this definition and Carroll’s indication that these abilities are typically measured with achievement tests. Most assessment professionals use the terms cognitive and achievement abilities in accordance with these definitions. However, the term aptitude is often misunderstood.
Carroll (1993) uses a narrow definition of aptitude—“to refer to a cognitive ability that is possibly predictive of certain kinds of future learning success” (p. 16; emphasis added). The functional emphasis on prediction is the key to this narrow definition of aptitude and is so indicated by the two horizontal arrows in the figure. These arrows, which connect the shaded CHC narrow abilities that are combined to predict an achievement ability outcome domain, are the definition of aptitude used in this paper.
This definition of aptitude is much narrower than the broader notion of aptitude as reflected in the work of Richard Snow. Snow’s notion of aptitude includes both cognitive and non-cognitive (conative) characteristics of individuals (Corno et al., 2002; Snow et al., 1996). This broader definition of aptitude focuses on human aptitudes which represent “the characteristics of human beings that make for success or failure in life's important pursuits. Individual differences in aptitudes are displayed every time performance in challenging activities is assessed” (Corno et al., 2002, p. xxiii). Contrary to many current assumptions, aptitude is not the same as ability. According to Corno et al. (2002), ability is the power to carry out some type of specific task and comes in many forms—reading comprehension, mathematical reasoning, spatial ability, perceptual speed, domain-specific knowledge (e.g., humanities), physical coordination, etc. This is consistent with Carroll’s definition of ability. According to Snow and colleagues, aptitude is more aligned with the concepts of readiness, suitability, susceptibility, and proneness, all which suggest a “predisposition to respond in a way that fits, or does not fit, a particular situation or class of situations. The common thread is potentiality—a latent quality that enables the development or production, given specified conditions, of some more advanced performance” (Corno et al., 2002, p. 3; see Scheffler, 1985). This broader definition includes non-cognitive characteristics such achievement motivation, freedom from anxiety, self-concept, control of impulses, and other (see Beyond IQ project).
As reflected in the model in the above figure, cognitive and achievement abilities differ primarily in the degree of emphasis on degree of mental information processing (cognitive) and the degree which the ability is an outcome acquired more from informal and formal instruction (achievement). Here, aptitude is defined as the combination, amalgam or complex of specific cognitive abilities that when combined best predict a specific achievement domain. Cognitive abilities are always cognitive abilities. Some cognitive abilities contribute to academic or scholastic aptitudes, which are pragmatic functional measurement entities—not trait-like cognitive abilities. Different academic or scholastic aptitudes, depending on the achievement domain of interest, likely share certain common cognitive abilities (domain-general) and also include cognitive abilities specific to certain achievement domains (domain-specific). A simple and useful distinction is that cognitive abilities and achievements are more like unique abilities in a table of human cognitive elements while different aptitudes represent combinations of different cognitive elements to serve a pragmatic predictive function. For the quantoid readers, the distinction between factor-analysis based latent traits (cognitive abilities) and multiple regression based functional predictors of achievement outcomes (cognitive aptitude) may help clarify the sometimes murky discussion of cognitive and achievement abilities and aptitudes.