The perception of natural contour.

The observation that natural curves and surfaces are often fractal suggests that people may be sensitive to their statistical properties. The perceptual protocols that underlie discrimination between fractals and between other types of random contour and fractals are examined. Discrimination algorithms that have precisely the same sensitivities as human observers are constructed. These algorithms do not recognize the integrated scale hierarchy intrinsic to fractal form and operate by imposing a metatheory of structure that is based on a signal–noise distinction. The success of the algorithms implies that (1) self-affinity in random fractals is not perceptually recovered and (2) people have a natural disposition to view contour in terms of signal and noise. The authors propose that this disposition be understood as a principle of perceptual organization. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interkey timing in piano performance and typing

In typing, when the fingers executing two successive movements are on the same hand, the time between keystrokes is longer than when the fingers are on different hands. Biomechanical limitations of the hands are thought to account for this difference. The generality of this finding was explored by investigating skilled pianists' performance of two successive notes. Experiment 1 failed to find comparable differences in timing as a function of the hands involved. Experiment 2, employing both a piano production and a typing task, replicated the previous piano performance results, and revealed that the timing differences in typing were limited to letter sequences requiring fore-aft and lateral finger movements. Experiment 3 extended this finding to piano performance. Together, these findings clarify the nature of biomechanical constraints on skilled manual performance.     

Synthetic Aspects of Selective Ion Exchangers

New anion exchange resins were prepared by the interaction of sulfonated and chloromethylated crosslinked polystyrene with hexamine, ethylene diamine, and thiourea. The conditions of preparation were based on existing information concerning the analogous monomers and were adapted to the special case of the polymeric matrix.     

Music cognition and performance: An introduction.

Introduces this issue of the Canadian Journal of Experimental Psychology as focusing on musical cognition and performance. There are a series of articles reporting on explorations of various aspects of the cognitive processing of music. Other articles focus on different aspects of the perceptual and cognitive processing of music. Also represented in this special issue is work looking at the emotional aspect of musical behaviour. Finally, this special issue contains two series of experiments related to musical performance, each, interestingly enough, with a developmental slant. Overall, the articles in this special issue provide insight into how it is that people perceive and produce complex auditory information, and are suggestive about what research in musical cognition can say about psychological processing in general. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pitch and time, tonality and meter: How do musical dimensions combine?

The authors examined how the structural attributes of tonality and meter influence musical pitch–time relations. Listeners heard a musical context followed by probe events that varied in pitch class and temporal position. Tonal and metric hierarchies contributed additively to the goodness-of-fit of probes, with pitch class exerting a stronger influence than temporal position (Experiment 1), even when listeners attempted to ignore pitch (Experiment 2). Speeded classification tasks confirmed this asymmetry. Temporal classification was biased by tonal stability (Experiment 3), but pitch classification was unaffected by temporal position (Experiment 4). Experiments 5 and 6 ruled out explanations based on the presence of pitch classes and temporal positions in the context, unequal stimulus quantity, and discriminability. The authors discuss how typical Western music biases attention toward pitch and distinguish between dimensional discriminability and salience. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory perception of fractal contours.

A series of experiments examined auditory contour formation, investigating listeners' sensitivities to a family of random fractals known as fractional Brownian noises. Exps 1A and 1B looked at identification of contours when 3 different noises were portrayed using variations in the pitch, duration, or loudness of successive notes of a sequence. Listeners could categorize pitch and loudness encodings, but not duration mappings. Exp 2 looked at the effect of simultaneous presentation of pitch and loudness information, finding that these dimensions combined additively to increase identification of the noise distributions. Exp 3 looked at discrimination of pitch contours as a function of changing fractal dimension. Discrimination curves approximated an inverted U shape, a finding that is not understandable in terms of sensitivity to differences in fractal dimension per se, nor in terms of "tuned" perceptual sensitivity to statistical regularities of the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of visual and body movement information in infant search.

Three experiments investigated the use of visual input and body movement input arising from movement through the world on spatial orientation. Infants between 9.5 and 18 months participated in a search task in which they searched for a toy hidden in 1 of 2 containers. Prior to beginning search, either the infants or the containers were rotated 180*; these rotations occurred in a lit or dark environment. These experiments were distinguished by the environmental cues for object location; Experiment 1 used a position cue, Experiment 2 a color cue, and Experiment 3 both position and color cues. Accuracy was better in Experiments 2 and 3 than in Experiment 1. All studies found that search was best after infant movement in the light; all other conditions led to equivalently worse performance. These results are discussed relative to a theoretical characterization of spatial coding focusing on the uses of spatial information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Connaissance et exécution de la musique: Introduction.

Here the issue of the Canadian Journal of Experimental Psychology devotes its knowledge to the execution of music. The interest and research on the knowledge and execution of music have increased considerably during the last decades. This field now has become one of the most dynamic sub-disciplines of psychology and musical thinking. To present such a concentration of articles offers many advantages. By presenting the work of several of the best researchers in this field, this issue offers an excellent general introduction to the readers who do not know this discipline well. As for the experts, they will find a concentration of practical results from very recent research. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

EXTRACTION OF COPPER SALTS WITH A MIXED EXTRACTANT

Equilibrium distribution measurements and spectroscopic studies were undertaken in order to investigate the extraction of copper salts into a mixed extractant consisting of 2-ethyl hexanoic acid and trioctylamine in toluene. The predominant species in the organic phase was found to be a large ion pair of the type [R₃NH⁺]₂[CuX₂(R'COO-)₂]A By contacting the copper-loaded organic phase with water, an aqueous salt solution, or dilute HCI, copper can easily be back-extracted into the aqueous phase.     

EXTRACTION OF COPPER SALTS WITH A MIXED EXTRACTANT (II): WATER UPTAKE AND OSMOMETRIC MEASUREMENTS

A mixture, consisting of trioctylamine and 2-ethyl hexanoic acid dissolved in toluene, extracts metal salts as well as water from aqueous salt solutions. Water uptake measurements showed a linear increase with salt concentration. IR spectra revealed -OH vibrations of both “free” and “associated” hydroxyl, which differ from those of bulk water. Data treatment of water uptake in accordance with Hogfeldt's model indicated the formation of mixed reversed micelles consisting of metal-salt-loaded mixed extractant and free extractant molecules. Micellization was also confirmed by osmometric measurements.