Developmental changes in auditory temporal perception

Infants, preschoolers, and adults were tested to determine the shortest time interval at which they would respond to the precedence effect--an auditory phenomenon produced by presenting the same sound through 2 loudspeakers with the input to 1 loudspeaker delayed relative to the other. The delayed sound is not localized at its source until time delays between onsets are lengthened beyond a critical limit, or threshold. Thresholds for the precedence effect were defined as the delay interval below which listeners respond only to the leading loudspeaker and above which they respond to both loudspeakers. Threshold estimates were determined for adults and preschoolers with an ascending and descending series, followed by a method of constant stimuli series. Infants were trained to respond to the delayed sound using a visually reinforced headturning procedure. For clicks, preschoolers' and adults' thresholds were around 12 msec, while 6-month-olds stopped responding to the delayed sound around 25 msec. A similar developmental difference in threshold was expressed between preschoolers and adults for a more complex sound, with younger subjects hearing the precedence effect over a longer time delay.     

Heading in the rat: Determination by environmental shape

After a 75-sec intratrial delay, rats that had been shown the location of hidden food within a rectangular box correctly dug at that location in a second identical box, which had been moved into the same position within the room. For some rats, the opposing ends of the boxes were differentiated by distinctive corner panels; for others, there were no panels. When, during the delay interval, the turntable supporting both boxes was rotated by more than 180°, so that the second box no longer took the place of the first box within the room, the rats showed performance decrements. Nevertheless, 4 subjects selected the correct location significantly more often than the rotationally equivalent location, which corresponds to the correct location when the ends of the box are confused. The amount of rotation had no significant effect for any rat. In a final phase, the rats were denied perceptual access to cues outside the test box, which now had differentiating corner panels for all rats. Despite the distinctive panels, no rat showed a significant difference between correct digs and rotational errors; that is, no rat reliably distinguished one end of the box from the other. Results confirm previous findings that rats rely primarily on environmental shape to establish their heading. They ignore distinctive features of the surfaces that define environmental shape, even when the shape by itself is insufficient to establish a unique orientation.     

Personality,Intelligence Components and Foreign Language Attainment

Approximately 1200 children from the Irish Republic were tested for various intelligence abilities, attainment in Irish (taught as a second language), personality traits of psychoticism, neuroticism and extroversion and attitude to learning foreign languages. Females had a significantly higher N score and had a significantly more positive attitude towards learning second languages and males had a significantly higher P score. The personality measures were not strongly related to the cognitive measures; anxiety, for example, does not appear to have an adverse effect on performance. There were low but positive correlations between attitude towards foreign language learning and the total score obtained in the Irish test. It is suggested that individuals have a more positive attitude towards subjects they are good at; hence the attitude could be influenced by innate ability. Attitude towards learning foreign languages also had low but significant correlations with some of the other cognitive tests, e.g. the English Spelling and Verbal Fluency tests. The results were very similar for both the primary and secondary school children. Age does not appear to influence personality measures during this period of childhood and adolescence.