Reaction Time under Different Stimulus Conditions

For military purposes it was desired to know the relation between two types of reaction time tests. These tests were: (1) a simple reaction time test of the usual type, (2) a clock reaction time test in which the subject attempted to stop the moving hand of a clock at a certain predesignated point on the face, by pressing a standard telegraph key. Seashore, Buxton, and McCollom (1940) have reported that certain factors corresponding to motor skills have been isolated in terms of qualitative similarity in the pattern of action, including perceptual activity, involved in various tests rather than to anatomical units such as the dominant sense-field, or even the musculature employed. Seashore, Starmann, Kendall, and Helmick (1941) found that both simple and discriminative reaction times for visual and auditory stimuli are included in a group factor of speeds of single reactions. The same authors, however, warn against extending this factor to include other kinds of reaction time without experimental verification

Egg-laying substrate selection for optimal camouflage by quail

Camouflage is conferred by background matching and disruption, which are both affected by microhabitat [1]. However, microhabitat selection that enhances camouflage has only been demonstrated in species with discrete phenotypic morphs [2 and 3]. For most animals, phenotypic variation is continuous [4 and 5]; here we explore whether such individuals can select microhabitats to best exploit camouflage. We use substrate selection in a ground-nesting bird (Japanese quail, Coturnix japonica). For such species, threat from visual predators is high [6] and egg appearance shows strong between-female variation [7]. In quail, variation in appearance is particularly obvious in the amount of dark maculation on the light-colored shell [8]. When given a choice, birds consistently selected laying substrates that made visual detection of their egg outline most challenging. However, the strategy for maximizing camouflage varied with the degree of egg maculation. Females laying heavily maculated eggs selected the substrate that more closely matched egg maculation color properties, leading to camouflage through disruptive coloration. For lightly maculated eggs, females chose a substrate that best matched their egg background coloration, suggesting background matching. Our results show that quail “know” their individual egg patterning and seek out a nest position that provides most effective camouflage for their individual phenotyp

Orientation to the sun by animals and its interaction with crypsis

1. Orientation with respect to the sun has been observed in a wide range of species and hasgenerally been interpreted in terms of thermoregulation and/or ultraviolet (UV) protection. For countershaded animals, orientation with respect to the sun may also result from the pres-sure to exploit the gradient of coloration optimally to enhance crypsis.2. Here, we use computational modelling to predict the optimal countershading pattern for anoriented body. We assess how camouflage performance declines as orientation varies using acomputational model that incorporates realistic lighting environments.3. Once an optimal countershading pattern for crypsis has been chosen, we determineseparately how UV protection/irradiation and solar thermal inflow fluctuate with orientation.4. We show that body orientations that could optimally use countershading to enhance crypsisare very similar to those that allow optimal solar heat inflow and UV protection.5. Our findings suggest that crypsis has been overlooked as a selective pressure on orientationand that new experiments should be designed to tease apart the respective roles of these different selective pressures. We propose potential experiments that could achieve this

Conservation Knowledge and Attitudes of Iowa Academy of Science Members

Over a year ago I received a letter asking if I would serve on an advisory committee to the Academy committee on conservation. The gist of the letter was that Academy members outside the fields usually associated with conservation might be helpful to the regular committee in an advisory capacity. If the aim was to secure members who were woefully ignorant of the field of conservation, mine was a happy choice for membership on the advisory committee. I so informed the secretary and was accepted anyway, so at least my conscience was clear. I felt that at least I could learn something whether or not I contributed positively to the Academy program on conservation

A Forced-Choice Rating Scale for College Instructors

The purpose of this study was to construct a forced-choice rating scale for evaluating students\u27 opinions of college instructors. The scale constructed consists of 20 tetrads, or groups of 4 statements descriptive of instructors. These statements were chosen so that a pair of favorable items, both appearing to be equally favorable, and a pair of unfavorable items, both appearing to be equally unfavorable, make up each tetrad. From each tetrad the rater must choose the item most characteristic and the item least characteristic of the ratee. The reason for choosing items in this manner can be seen in Sisson\u27s statement of the basic assumptions underlying the forced-choice method, which was used in rating Army officers

A Comparison of the Minnesota Personality Scale and the Bell Adjustment Inventory for Student Counseling

The purpose of this study is to report the findings concerning the comparative diagnostic value of two personality tests, the Bell Adjustment Inventory (Student form) and the Minnesota Personality Scale, for use in student counseling. The Bell Adjustment Inventory has been used for the past six years as a part of the battery of tests given during New Student Days at Grinnell College, with apparently satisfactory results. However, with the development of the new Minnesota Personality Scale, it was felt by the college personnel department that perhaps this test would prove of even greater diagnostic value in the counseling program

Three-dimensional camouflage:exploiting photons to conceal form

Many animals have a gradation of body color, termed “countershading,” where the areas that are typically exposed to more light are darker. One hypothesis is that this patterning enhances visual camouflage by making the retinal image of the animal match that of the background, a fundamentally two-dimensional theory. More controversially, countershading may also obliterate cues to three-dimensional (3D) shape delivered by shading. Despite relying on distinct cognitive mechanisms, these two potential functions hitherto have been amalgamated in the literature. It has previously not been possible to validate either hypothesis empirically, because there has been no general theory of optimal countershading that allows quantitative predictions to be made about the many environmental parameters involved. Here we unpack the logical distinction between using countershading for background matching and using it to obliterate 3D shape. We use computational modeling to determine the optimal coloration for the camouflage of 3D shape. Our model of 3D concealment is derived from the physics of light and informed by perceptual psychology: we simulate a 3D world that incorporates naturalistic lighting environments. The model allows us to predict countershading coloration for terrestrial environments, for any body shape and a wide range of ecologically relevant parameters. The approach can be generalized to any light distribution, including those underwater

Stacking chairs:local sense and global nonsense

We report a confusing stimulus which demonstrates the power of local interpretation of threedimensional structure to disrupt a coherent global perception

Optimizing countershading camouflage

Countershading, the widespread tendency of animals to be darker on the side that receives strongest illumination, has classically been explained as an adaptation for camouflage: obliterating cues to 3D shape and enhancing background matching. However, there have only been two quantitative tests of whether the patterns observed in different species match the optimal shading to obliterate 3D cues, and no tests of whether optimal countershading actually improves concealment or survival. We use a mathematical model of the light field to predict the optimal countershading for concealment that is specific to the light environment and then test this prediction with correspondingly patterned model “caterpillars” exposed to avian predation in the field. We show that the optimal countershading is strongly illumination-dependent. A relatively sharp transition in surface patterning from dark to light is only optimal under direct solar illumination; if there is diffuse illumination from cloudy skies or shade, the pattern provides no advantage over homogeneous background-matching coloration. Conversely, a smoother gradation between dark and light is optimal under cloudy skies or shade. The demonstration of these illumination-dependent effects of different countershading patterns on predation risk strongly supports the comparative evidence showing that the type of countershading varies with light environment