Although psychology is the science of mental life and behavior, it has paid little attention to the means by which mental life is translated into behavior. One domain where links between cognition and action have been explored is the manipulation of objects. This article reviews psychological research on this topic, with special emphasis on the tendency to grasp objects differently depending on what one plans to do with the objects. Such differential grasping has been demonstrated in a wide range of object manipulation tasks, including grasping an object in a way that reveals anticipation of the object's future orientation, height, and required placement precision. Differential grasping has also been demonstrated in a wide range of behaviors, including one-hand grasps, two-hand grasps, walking, and transferring objects from place to place as well as from person to person. The populations in whom the tendency has been shown are also diverse, including nonhuman primates as well as human adults, children, and babies. Meanwhile, the tendency is compromised in a variety of clinical populations and in children of a surprisingly advanced age. Verbal working memory is compromised as well if words are memorized while object manipulation tasks are performed; the recency portion of the serial position curve is reduced in this circumstance. In general, the research reviewed here points to rich connections between cognition and action as revealed through the study of object manipulation. Other implications concern affordances, Donders' Law, and naturalistic observation and the teaching of psychology.

Humans (Homo sapiens) anticipate the consequences of their forthcoming actions. For example, they grasp objects with uncomfortable grasps to afford comfortable end positions-the end-state comfort (ESC) effect. When did such sophisticated motor planning abilities emerge in evolution? We addressed this question by asking whether humans' most distant living primate relatives-lemurs-also exhibit the ESC effect. We presented 6 species of lemurs (Lemur catta, Eulemur mongoz, Eulemur coronatus, Eulemur collaris, Hapalemur griseus, and Varecia rubra) with a food extraction task and measured the grasp used-either a canonical thumb-up posture or a noncanonical thumb-down posture. The lemurs adopted the thumb-down posture when that hand position afforded a thumb-up posture following object transport, thereby exhibiting the ESC effect. We conclude that the planning abilities underlying the ESC effect evolved at least 65 million years ago, or 25 million years earlier than previously supposed based on an earlier demonstration of the ESC effect in cotton-top tamarins (Saguinus oedipus; Weiss, Wark, & Rosenbaum, 2007). Because neither cotton-tops nor lemurs are tool users, the data suggest that the cognitive abilities implicated by the ESC effect are not sufficient, although they may be necessary, for tool use.

Research methods and statistics are core courses in the undergraduate psychology major. To assess learning outcomes, it would be useful to have a measure that assesses research methods and statistical literacy beyond course grades. In two studies, we developed and provided initial validation results for a research methods and statistical knowledge concept inventory for eventual use in further scholarship of teaching and learning. In Study 1, we created vignettes and administered open-ended questions to psychology subject pool students. In Study 2, we refined the vignettes and created multiple-choice items using participant responses from Study 1. After administering the measure to psychology subject pool students and a community-based sample of Amazon Mechanical Turk workers, we used item response theory to select 20 items to compose the final Psychological Research Inventory of Concepts.

Actions that are chosen have properties that distinguish them from actions that are not. Of the nearly infinite possible actions that can achieve any given task, many of the unchosen actions are irrelevant, incorrect, or inappropriate. Others are relevant, correct, or appropriate but are disfavored for other reasons. Our research focuses on the question of what distinguishes actions that are chosen from actions that are possible but are not. We review studies that use simple preference methods to identify factors that contribute to action choices, especially for object-manipulation tasks. We can determine which factors are especially important through simple behavioral experiments.

The current set of three studies further evaluates the validity and application of the Psychological Research Inventory of Concepts (PRIC). In Study 1, we administered the PRIC to a sample of introductory psychology students and online (Mechanical Turk) participants along with measures assessing theoretically related concepts. We found evidence of concurrent validity by demonstrating that PRIC scores relate to education, cognitive effort, and general psychological knowledge. In Study 2, we demonstrated that advanced psychology majors score higher on the PRIC than college graduates who did not major in psychology, suggesting that the PRIC assesses domain-specific knowledge and may be useful in assessment of the undergraduate psychology major. Finally, in Study 3, we demonstrated that scores on the PRIC increase from the start to the end of a research methods course. Together, these studies provide further evidence that the PRIC may be a useful index of learning research methods and statistical knowledge important for the undergraduate psychology degree.