Intuitive physics: the straight-down belief and its origin

This study examines the nature and origin of a common misconception about moving objects. We first show through the use of pencil-and-paper problems that many people erroneously believe that an object that is carried by another moving object (e.g., a ball carried by a walking person) will, if dropped, fall to the ground in a straight vertical line. (In fact, such an object will fall forward in a parabolic arc.) We then demonstrate that this "straight-down belief" turns up not only on pencil-and-paper problems but also on a problem presented in a concrete, dynamic fashion (Experiment 1) and in a situation in which a subject drops a ball while walking (Experiment 2). We next consider the origin of the straight-down belief and propose that the belief may stem from a perceptual illusion. Specifically, we suggest that objects dropped from a moving carrier may be perceived as falling straight down or even backward, when in fact they move forward as they fall. Experiment 3, in which subjects view computer-generated displays simulating situations in which a carried object is dropped, and Experiment 4, in which subjects view a videotape of a walking person dropping an object, provide data consistent with this "seeing is believing" hypothesis.     

PC-compatible computer-generated stimuli for video-task testing

Whereas computer technology allows for the automation of experimentation and data collection, the process of stimulus production has remained a relatively, labor-intensive process. A program for automatic computer generation of novel nonverbal stimuli is described in this paper. The program, STIMGEN, allows menu-driven control over the type and appearance of stimuli. Data are presented in which two monkeys matched to sample with high accuracy using stimuli generated with STIMGEN. These data are interpreted to support the usefulness and value of automatic stimulus generation in a variety of applications.     

Specific-token effects in screening tasks: possible implications for aviation security

Screeners at airport security checkpoints perform an important categorization task in which they search for threat items in complex x-ray images. But little is known about how the processes of categorization stand up to visual complexity. The authors filled this research gap with screening tasks in which participants searched for members of target categories in visual displays. The authors found that when targets were sampled with replacement and repetition, participant screeners relied on recognizing familiar targets and had great difficulty using category-general knowledge. The authors observed a "heartbeat" in detection performance--it improved while test images repeated but dropped sharply when unfamiliar targets from the same categories appeared. This reliance on familiarity illuminates the processes of categorization under conditions of visual complexity and suggests limits on those processes. This reliance also has implications for the training and evaluation of screeners in the field.     

Category learning in rhesus monkeys: a study of the Shepard, Hovland, and Jenkins (1961) tasks

In influential research, R. N. Shepard, C. I. Hovland, and H. M. Jenkins (1961) surveyed humans' categorization abilities using tasks based in rules, exclusive-or (XOR) relations, and exemplar memorization. Humans' performance was poorly predicted by cue-conditioning or stimulus-generalization theories, causing Shepard et al. to describe it in terms of hypothesis selection and rule application that were possibly supported by verbal mediation. The authors of the current article surveyed monkeys' categorization abilities similarly. Monkeys, like humans, found category tasks with a single relevant dimension the easiest and perceptually chaotic tasks requiring exemplar memorization the most difficult. Monkeys, unlike humans, found tasks based in XOR relations very difficult. The authors discuss the character and basis of the species difference in categorization and consider whether monkeys are the generalization-based cognitive system that humans are not.     

Rhesus macaques (Macaca mulatta) categorize unknown conspecifics according to their dominance relations

The authors trained 3 adult male rhesus macaques (Macaca mulatta) to categorize pairs of unknown conspecifics presented in a video according to the dominance status of the videotaped monkeys. The subjects were trained to choose the dominant monkey for a category of films (e.g., films showing 1 monkey chasing another); then, new films were presented involving different conspecifics, and the monkeys' first responses to this new category of behavior (e.g., monkeys fighting) were taken as evidence of transfer. Two subjects were able to generalize categorical judgments of dominance to new films involving new behaviors. These findings seem to indicate that monkeys can use abstract social concepts and are aware of the social relationships within their group.     

Stimulus Movement and the Intensity of Attention

The Psychological Record - A stimulus movement effect has been reported in which learning by nonhuman animals was significantly better with moving than with stationary stimuli. In the present...     

Stroop-like effects for monkeys and humans: processing speed or strength of association?

Abstract— Stroop-like effects have been found using a variety of paradigms and subject groups In the present investigation, 6 rhesus monkeys (Macaca mulatta) and 28 humans exhibited Stroop-like inserference and facilitation in a relativenumerousness task Monkeys, like humans, processed the meanings of the numerical symbols automatically—despite the fact that these meanings were irrelevant to task performance These data also afforded direct comparison of interpretations of the Stroop effect in terms of processing speed versus association strength These findings were consistent with parallel-processing models of Stroop-like interference proposed elsewhere, but not with processing-speed accounts posited frequently to explain the effect     

Rhesus macaques (Macaca mulatta) monitor uncertainty during numerosity judgments

Two rhesus macaques (Macaca mulatta) judged arrays of dots on a computer screen as having more or fewer dots than a center value that was never presented in trials. After learning a center value, monkeys were given an uncertainty response that let them decline to make the numerosity judgment on that trial. Across center values (3-7), errors occurred most often for sets adjacent in numerosity to the center value. The monkeys also used the uncertainty response most frequently on these difficult trials. A 2nd experiment showed that monkeys' responses reflected numerical magnitude and not the surface-area illumination of the displays. This research shows that monkeys' uncertainty-monitoring capacity extends to the domain of numerical cognition. It also shows monkeys' use of the purest uncertainty response possible, uncontaminated by any secondary motivator.     

Dissociating uncertainty responses and reinforcement signals in the comparative study of uncertainty monitoring

Although researchers are exploring animals' capacity for monitoring their states of uncertainty, the use of some paradigms allows the criticism that animals map avoidance responses to error-causing stimuli not because of uncertainty monitored but because of feedback signals and stimulus aversion. The authors addressed this criticism with an uncertainty-monitoring task in which participants completed blocks of trials with feedback deferred so that they could not associate reinforcement signals to particular stimuli or stimulus-response pairs. Humans and 1 of 2 monkeys were able to make cognitive, decisional uncertainty responses that were independent of feedback or reinforcement history within a task. This finding unifies the comparative literature on uncertainty monitoring. The dissociation of performance from reinforcement has theoretical implications, and the deferred-feedback technique has many applications.