Chicks prefer to peck at insect-like elongated stimuli moving in a direction orthogonal to their longer axis

Spontaneous preferences towards possible prey have been little investigated using targets in motion. Preferences of domestic chicks (Gallus gallus) to peck at video-images of stimuli representing live insects moving along their longer body axis (i.e. “forwards”) or along the shorter body axis (i.e. “sideways”) were investigated. Chicks presented with both types of stimulus displayed a significant preference for pecking at stimuli moving sideways. This preference was already present on day 1 post-hatching, and it strengthened on day 6 for those chicks that had experienced pecking at live insects. Head angles used to fixate the stimuli prior to pecking were also analysed and were consistent (i.e. 30°–35° and 60°–65°) with those reported for fixation of non-edible targets (larger stimuli at a distance). In a first control experiment the same video-presented stimuli were used but the insect’s legs were removed to reduce flickering. In a second control experiment, paper-printed images of the whole insect were used. In both cases, the sideways direction of movement was clearly preferred. Overall, our data show that chicks have a spontaneous preference to peck at video-images resembling live insects moving along their shorter body axis. Sideways movement may constitute a crucial signal attracting chicks’ attention and enhancing predatory responses possibly because of stronger stimulation of motion detectors.     

Mom’s shadow: structure-from-motion in newly hatched chicks as revealed by an imprinting procedure

The ability to recognize three-dimensional objects from two-dimensional (2-D) displays was investigated in domestic chicks, focusing on the role of the object’s motion. In Experiment 1 newly hatched chicks, imprinted on a three-dimensional (3-D) object, were allowed to choose between the shadows of the familiar object and of an object never seen before. In Experiments 2 and 3 random-dot displays were used to produce the perception of a solid shape only when set in motion. Overall, the results showed that domestic chicks were able to recognize familiar shapes from 2-D motion stimuli. It is likely that similar general mechanisms underlying the perception of structure-from-motion and the extraction of 3-D information are shared by humans and animals. The present data shows that they occur similarly in birds as known for mammals, two separate vertebrate classes; this possibly indicates a common phylogenetic origin of these processes.     

Studies on time: a proposal on how to get out of circularity

The analysis of time is vitiated very often by circularity: several disciplines, such as psychology, linguistics, and neurosciences, analyze time by using concepts or terms which already contain in themselves, or are based, on the experience and notion of time (as when, for example, time is defined as “duration”, or when our ability to estimate durations is explained by resorting to the notion of an internal clock). Some detailed examples of circularity in the analysis of time are given here and examined. A way out of circularity is then given: it is represented by the proposal of attentional semantics (AS) of considering words and their meanings in terms of the aim they serve, and the means and processes developed and implemented in order to achieve that aim. According to AS, the main aim of words is that of indicating to, and eliciting in, the listener or reader a specific conscious experience: namely, the conscious experience referred to by their meanings. Words achieve their main aim by conveying the condensed instructions on the attentional operations one has to perform if one wants to consciously experience what is expressed through and by them. By describing the conscious experiences elicited by words in terms of the attentional operations that are responsible for the production of such conscious experiences, AS offers an a-linguistic counterpart to language, and therefore an effective way out of circularity. Following in footsteps of Mach (Contributions to the analysis of the sensations, 1890), but slightly revising his hypothesis, AS defines time-sensation as the perception of the effort made, or alternatively the nervous energy expended, by the organ of attention when performing a “temporal activity” (for instance, estimating duration), that is, when one’s own attention is focused in a continuous and incremental way on the conscious product of the (“non-temporal”) activity performed by means of another portion of one’s attention.

Differences in matching-to-sample performance with element and compound sample stimuli in pigeons

This series of experiments examined zero-delay matching-to-sample performance in pigeons with element and compound sample stimuli. In Experiment 1, compound sample stimuli were consistently followed by compound comparison stimuli and matching accuracy during testing was equivalent to element sample-element comparison trials on the color dimension. In Experiment 2, element comparisons suddenly introduced following compound samples produced a decrement on the line dimension only. Subsequent testing at various sample durations revealed higher matching accuracy following element samples than following compound samples on both the color and line-tilt dimensions. Experiment 3 replicated the results of Experiments 1 and 2 and also demonstrated that the superiority of element over compound matching performance remains constant over the sample durations tested. In Experiment 4 testing at sample durations up to 30 sec produced an overall decrement in matching performance, but again the element vs compound matching difference remained constant. The stimulus-generalization decrement hypothesis provided a better explanation of these results than either the information-overload hypothesis or the rule hypothesis.     

Brain rCBF and performance in visual imagery tasks: Common and distinct processes

The present study was designed to discover whether variations in normalised regional cerebral blood flow (rCBF) in different brain areas predict variations in performance of different imagery tasks. Positron emission tomography (PET) was used to assess brain activity as 16 participants performed four imagery tasks. These tasks were designed so that performance was particularly sensitive to the participant's ability to form images with high resolution, to generate images from distinct segments, to parse imaged forms into parts while inspecting them, or to transform (rotate) images. Response times and error rates were recorded. Multiple regression analyses revealed that variations in most brain areas predicted variations in performance of only one task, thus demonstrating that the four tasks tap largely independent imagery processes. However, we also found that some underlying processes were recruited by more than one task, particularly those implemented in the occipito‐parietal sulcus, the medial frontal cortex, and Area 18.     

Domestic chicks perceive stereokinetic illusions

Stereokinetic illusions occur when certain 2-D patterns are set in slow rotation in a plane perpendicular to the line of sight. Such phenomena have never been investigated in animal species other than our own. We used the domestic chick (Gallus gallus) to check whether these illusions are experienced by non-human species, taking advantage of filial imprinting. Newly hatched visually naive chicks were individually exposed for 4 h to 2-D stimuli producing, to a human observer, the perception of a stereokinetic cone (experiment 1) or of a stereokinetic cylinder (experiment 2). Thereafter, each chick underwent a free-choice test between a solid 3-D cone and a solid 3-D cylinder. A control group of newly hatched but not imprinted chicks underwent the same testing procedure, to check for the presence of any spontaneous preference for one or other of the two solid objects. Imprinted chicks approached the 3-D stimulus closely resembling the stimulus they had been exposed to during imprinting (the cone in experiment 1 and the cylinder in experiment 2). Non-imprinted chicks did not show any preference. These results suggest that domestic chicks experience stereokinetic illusions.     

Dissecting the geometric module: a sense linkage for metric and landmark information in animals' spatial reorientation

Disoriented children can use geometric information in combination with featural information to reorient themselves in large but not in small spaces; somewhat similar effects have been found in nonhuman animals. These results call for an explanation. We trained young chicks to reorient to find food in a corner of a small or a large rectangular room with a distinctive featural cue (a blue wall) -- a task similar to that used with children. Then we tested the chicks after displacement of the feature to an adjacent wall. In the large enclosure, chicks chose the corner that maintained the correct arrangement of the featural cue with respect to sense, whereas in the small enclosure, they chose the corner that maintained the correct metrical arrangement of the walls with respect to sense. On the basis of these findings, we propose a simple model that can explain the effects of room size on spatial reorientation.     

Attachment predicts treatment completion in an eating disorders partial hospital program among women with anorexia nervosa

The goal of this study was to examine if attachment theory can provide a framework for understanding treatment completion in an eating disorders partial hospital program among women with anorexia nervosa (AN). Attachment was measured using the Attachment Styles Questionnaire (Feeney, Noller, & Hanrahan, 1994). As hypothesized, self-reports of high avoidant attachment predicted noncompletion of treatment for those with AN binge-purge subtype (ANB). However, this relationship did not emerge for those with AN restricting subtype (ANR). Also as hypothesized, self-reports of high anxious attachment predicted completing treatment for those with ANB but not for those with ANR. For completers with ANB and ANR, the program was helpful in increasing body weight and lowering drive for thinness, body dissatisfaction, interpersonal problems, and depression. Attachment avoidance, characterized by devaluing one's need for relationships, may be a contraindication for group-based partial hospital treatment of ANB. Attachment anxiety, characterized by high preoccupation with relationships, may facilitate remaining in treatment for those with ANB.