The rattling sound of rattlesnakes (Crotalus viridis) as a communicative resource for ground squirrels (Spermophilus beecheyi) and burrowing owls (Athene cunicularia)

Animal communication involves very dynamic processes that can generate new uses and functions for established communicative activities. In this article, the authors describe how an aposematic signal, the rattling sound of rattlesnakes (Crotalus viridis), has been exploited by 2 ecological associates of rattlesnakes: (a) California ground squirrels (Spermophilus beecheyi) use incidental acoustic cues in rattling sounds to assess the danger posed by the rattling snake, and (b) burrowing owls (Athene cunicularia) defend themselves against mammalian predators by mimicking the sound of rattling. The remarkable similarity between the burrowing owl's defensive hiss and the rattlesnake's rattling reflects both exaptation and adaptation. Such exploitation of the rattling sound has favored alternations in both the structure and the deployment of rattling by rattlesnakes.     

Do California ground squirrels (Spermophilus beecheyi) use ritualized syntactic cephalocaudal grooming as an agonistic signal?

Animal communication theory holds that many signals have evolved from nonsignal precursors. This field and laboratory study of California ground squirrels (Spermophilus beecheyi) provides evidence for the coexistence of such a precursor with its derived display. The precursor is an ancient, endogenously sequenced (syntactic) pattern of cephalocaudal grooming movements (CCGs) shared by all rodent suborders. The following evidence supports the hypothesis that a supernormal version of this pattern has been selected for signal function. Syntactic CCGs in the field (a) were more rigidly stereotyped than ordinary syntactic CCGs in the laboratory; (b) differed from laboratory syntactic CCGs in other ways that enhanced their conspicuousness, in part through exaggeration of the syntactic cephalocaudal pattern; (c) were associated with scent marking and social staring; and (d) were associated with intrasexual agonistic encounters that did not escalate to fighting.     

Measuring reaction time with millisecond accuracy using the TRS-80 microcomputer

A machine language subroutine is proposed for measuring reaction time with millisecond accuracy using the TRS-80 microcomputer. This timer is accurate to 1 msec in the first 30,000 msec and to 5 msec in the first 65,000 msec (1 part in 10,000).     

The Role of Rumination in Predicting Seasonality

The impact of the changing seasons on mood and behavior (i.e., seasonality) has long been of interest to researchers. Recently, researchers have begun to look beyond biological explanations to investigate psychological variables that may play a role in the development of seasonal affective disorder (SAD) and subsyndromal (S-SAD) levels of seasonality. Rumination, in particular, has received initial support as a process that predicts more severe levels of winter depression. In the first study, we assessed the effects of rumination, current weather conditions, current level of depression, and attitudes toward weather conditions as predictors of seasonality. In addition to weather conditions, weather attitudes, and current depression, rumination emerged as a significant predictor of seasonality in females but not for males. In the second study, we followed individuals categorized as being high (S-SAD) and low in seasonality over time and assessed for depression at Time 1 and Time 2. Rumination, in addition to current weather conditions and weather attitudes, emerged as a significant predictor of depression for females in the S-SAD group. The results of these studies provide support for the role of rumination in seasonal depression, particularly for females. This type of research may contribute to attempts to better explain gender differences in seasonal depression.     

Decision theory with complex uncertainties

A case is made for supposing that the total probability accounted for in a decision analysis is less than unity. This is done by constructing a measure on the set of all codes for computable functions in such a way that the measure of every effectively accountable subset is bounded by a number <1. The consistency of these measures with the Savage axioms for rational preference is established. Implications for applied decision theory are outlined.     

Hemispheric asymmetries in interpreting forms vs colors in ambiguous patterns

Prior to receiving briefly lateralized presentations of ambiguous visual patterns (Rorschach inkblots), 28 normal right-handed males heard two words, each describing a different interpretation of the pattern, e.g., one word might describe an interpretation based on attending to shapes or forms (form choices) and the other might describe an interpretation based on attending to chromatic color (e.g., color choices). Color choices were more frequent than form choices on left-hemisphere (LH) presentations of the patterns, and form choices were more frequent than color choices on right-hemisphere (RH) presentations. These results were interpreted as consistent with the theory that the LH's favored mental representation is semantic (i.e., frequent choices of concepts associated with names of colors in the patterns) and the RH's favored representation is imaginal (i.e., frequent choices of concepts associated with difficult-to-label forms in the patterns).     

Levels of processing, encoding strategies, and memory development.

In three experiments, memory for intentionally encoded words was compared with memory for encodings induced by asking semantic, phonemic, or surface questions. Subjects were second-, fourth-, and sixth-grade, and junior and senior high school students. Semantic encodings were more often recalled and recognized than were phonemic and surface (which did not differ). Intentional encodings were as likely to be recalled as semantic but were no more likely than phonemic and surface to be recognized, and this was true whether intentional learning was in anticipation of a recall test or a recognition test. Age trends occurred for recall, for intentional learning, and for induced processing which required subjects to generate word attributes. Age trends were attenuated for recognition and for induced processing which required subjects to verify whether a give attribute applied to the target word.     

Memory scanning of shapes,colors, and compounds: A comparison of retarded and nonretarded adults

Three experiments were performed to assess memory scanning of shapes, colors, and shape-color compounds by retarded and nonretarded people. Attributes comprising compounds provided either redundant or nonredundant information. Large retarded-nonretarded differences in reaction time were obtained. In contrast to previous reports of slow scanning of digits and nonsense shapes by retarded people, scan rates for shapes and colors did not differ between groups. Retarded subjects were not characterized by a deficient scan rate. Although compound stimuli required twice as many attributes in their repersentation as did simple stimuli, they were not scanned more slowly, indicating that per item scan rate is not determined by the number of attributes required to define each item. Both groups were able to exploit redundant relevant information to achieve faster processing than in simple conditions. Decision rules for rejecting compound stimuli comprised one, two, or more binary tests. Groups did not differ in speed of performing elementary binary test(s).     

Latent Trait Modeling with the Common beliefs Survey III: Using Item Response Theory to Evaluate an Irrational Beliefs Inventory

Assessment of irrational beliefs by such measures as the Common Beliefs Survey III (CBS) has traditionally relied upon classical test theory assumptions, in which the properties of specific test items are less important than the total test score as the aggregate of all item responses. An alternative approach using item response theory (IRT) methodology allows one to specify the parameters of difficulty and discrimination for each test item. Difficulty levels of CBS items range along a continuum of irrationality, the implied latent trait measured by responses to the questionnaire as a whole. We evaluated the CBS responses of 605 individuals from clinical and college settings, drawing from current and archival data. The original Likert scale ratings were recoded into dichotomous scores. Fourteen of the 54 items were highly or very highly discriminating in distinguishing respondents with high and low irrationality levels. However, discriminating items exhibited a very narrow range of difficulty; most functioned at a point a little above the halfway mark on the continuum of irrationality. Item characteristic curves and test information curves were very similar for female (n = 424) and male (n = 179) respondents. We derived a 4-item screening test for irrationality from our IRT analyses of the 54 CBS items. Further test development, focused on the selection and scaling of items with a much broader range of difficulty, would facilitate evaluation of the hierarchical structure of irrational beliefs. Portions of this paper were presented at the 39th Annual Convention of the Association for Behavioral and Cognitive Therapies, Washington, DC, November, 2005.