Visual search for simple volumetric shapes

Five experiments measured reaction time (RT) to detect the presence or absence of a simple volumetric shape (target) dependent on the number of display items (distractors) and their depicted three-dimensional (3-D) orientation. Experiments 1–4 examined every pairwise combination of two different simple volumetric shapes in two 3-D orientations. Conditions exhibiting “pop-out” could be predicted by differences in their two-dimensional (2-D) features. Conditions in which search was slower support previously found search asymmetries for particular 2-D features. When the distractors were a mixture of the other shapes in the same 3-D orientation, search was serial, except when the target had a curved principal axis (Experiment 5). The results suggest that these simple volumetric shapes are not processed preattentively.     

A new method of monitoring motor activity in baboons

Movement activity of a normal baboon and of a baboon with induced Parkinsonism by unilateral administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) was recorded by the Walter Reed Activity Monitor (or actigraph). Mean activity in the lesioned baboon was 41% less than that of the nonlesioned baboon measured over a 14-day period. In addition, the daily maximum activity value was significantly less in the MPTP-treated baboon. Moreover, resting and sleeping periods were 30% greater in the lesioned animal. The akinesia and resting and sleeping periods were displayed by the lesioned baboon throughout the day, whereas the control baboon showed them only at night. The data representing summarized movement activity are in accordance with observations of bradykinesia, hypokinesia, and akinesia of the MPTP-treated baboon. The actigraph was well tolerated by the animal because its small size and weight made it largely unobtrusive. We suggest that the actigraph is an appropriate device for measuring motor activity in nonhuman primates.     

The effect of enactment on memory for order

The effect of enactment on memory for serial order was investigated in two experiments. In both experiments a reconstruction task was used to separate order from item information. In Experiment 1 enactment and test information was manipulated between groups. For subjects who had not been informed about the reconstruction test, performance of verbal and motor groups was similar with regard to both serial-position curves and overall performance. For subjects who knew beforehand that they would be tested for memory of the order of the action events, performance in the verbal condition was significantly better than in the motor condition. In Experiment 2, the reversed enactment effect for test-informed subjects was replicated with a within-subjects design. The results agree with Engelkamp and Zimmer's (1984, 1994) position that enactment serves exclusively to enhance item information, and indicate that subjects have less control over the encoding processes when they are enacting than during verbal encoding (cf. Cohen, 1981).     

Money and the medical profession

Money motivates people, lubricates the movement of resources, mobilizes talent, and breaks down some barriers. But money also has a darker side; it can distract, corrupt, distort, and cruelly exclude. Money is a useful but unruly servant; sometimes, a hard master. The professional, at least in part, belongs to the world of money. We sometimes distinguish the amateur from the professional in that the amateur does it for love; the professional, for money. The professional has one foot in the marketplace, but also, purportedly, professes something else -- beyond the bottom line. The following discussion explores the morally complex ties and tensions between money and the medical professions.     

Attentional bias in anxiety: selective search or defective filtering?

Two experimental tasks were used to investigate the nature of a previously documented bias in attention associated with anxiety. Results from the first task failed to reveal any differences between anxious and nonanxious subjects, either in attention focusing or selective search for letters. The second task, with words as targets and distractors, suggested that selective search was less efficient in anxious subjects when distractors were present. Currently anxious subjects were slower than controls when required to search for the target among distractors of any type, whereas both currently anxious and recovered subjects were slower when the distractors were threatening words. It was therefore suggested that a bias favoring threat cues during perceptual search is an enduring feature of individuals vulnerable to anxiety, rather than a transient consequence of current mood state alone.     

Visual persistence of spatially filtered images

Periodic stimuli such as sine-wave gratings and checkerboard patterns have been used in many studies of visual perception. It is well known that with such stimuli, visual persistence increases as spatial frequency increases and as contrast decreases. It is not clear, however, that similar relationships obtain for aperiodic stimuli such as natural images. Digitized images of objects (a face and a vase) were submitted to two-dimensional Fourier analysis. Four pairs of spatial frequency band-limited images were created for each image. Each pair consisted of a normal (NP) and a scrambled (SP) phase version, with the magnitude spectrum and space-averaged luminance the same within each pair. Filter bandwidths were one octave wide. Threshold persistence was measured for each spatially filtered image. Visual persistence for SP images increased significantly as spatial frequency increased, whereas no significant differences were found for NP images. This suggests that the temporal processing of complex, aperiodic visual images is influenced by the spatial frequency and contrast of local features within the image and cannot be predicted by space-averaged estimates of contrast and spatial frequency.     

The effects of spatial phase on reaction time to spatially filtered images

Summary Many studies of visual perception have used periodic stimuli such as sine-wave gratings and checker-board patterns. It is well known that reaction time (RT) to such stimuli increases with increasing spatial frequency and decreasing contrast. While this is the case with periodic stimuli it is not clear that these relationships obtain for aperiodic stimuli such as natural scenes. A digitized image of an object (a vase) was submitted to two-dimensional Fourier analysis. Four pairs of spatial frequency band-limited images were created for each image. Each pair consisted of a normal-phase (NP) and a scrambled-phase (SP) version, with the magnitude spectrum and space-averaged luminance the same within each pair. Filter band-widths were 1 octave wide. Manual RT was measured for onset and offset of each spatially filtered image. Mean RT for SP images increased significantly with increasing spatial frequency, while no other significant differences were found with the NP images. This suggests that the temporal processing of complex, aperiodic images is influenced by the spatial frequency and contrast of local regions within the image, rather than by the space-averaged contrast of the entire image, and cannot be predicted by global estimates of contrast and spatial frequency.     

The impact of computers on cognitive psychology

Computer developments and their applications in cognitive psychology are reviewed. Examples from recent studies illustrate the ways that computers are used for different research purposes: stimulus generation, on-line interactive experimental control, response collection, data analysis, and theory building. A quantitative analysis of federal funding for computer-based and noncomputer research compares costs over the past 9 years for the areas of perception, memory, learning, and thinking. A tabulation of journal articles relevant to computer-based cognitive research shows the distribution of articles over various categories of hardware and software development. Finally, the advantages and disadvantages of using computers in cognitive research are evaluated.