Magnitude versus parity in numerical judgements: event-related brain potentials implicate response conflict as the source of interference.

When subjects make 'odd/even' and 'low/high' decisions about digits, information about the digit's magnitude can interfere with the decision about the digit's parity. The present experiment used a psychophysiological approach to examine whether this interference arises at the level of response processing. Subjects performed a choice-reaction time task involving low/high and odd/even judgements about the digits 2 through 9. The data point to a response locus for the interference effect with the size of the effect being dependent on the ease with which magnitude information can be used to prime the appropriate response. This, in turn, is influenced by the 'naturalness' of the mapping between magnitude and response hand as well as by the distance of a digit to the low/high cut-point.

Perinatal mortality--a hospital based study.

A total of 5082 consecutive deliveries in Medical College Hospital, Kottayam during the period August 1992 to July 1993 constituted the study. Perinatal mortality rate (PMR) was 38.5 per 1000 total births and autopsy rate was 72%. More than 85% of perinatal deaths occured in low birth weight and preterm babies. Perinatal hypoxia and congenital anomalies were the leading causes in late fetal deaths (LFD). The main causes of early neonatal deaths (END) were perinatal hypoxia, infections, congenital anomalies and hyaline membrane disease (HMD).

The cuing and priming of cognitive operations.

The effect on performance of advance information about the specific cognitive operations to be performed on a stimulus was investigated in two experiments using cues (information useful and necessary for performance) and primes (information useful but not necessary for performance). In the first experiment, a cue presented prior to a digit stimulus indicated whether the digit was to be classified as odd or even, or low (less than 6) or high (greater than 5). Results showed that performance improved with increasing time between cue and digit and with practice. A stroop-like asymmetric interference of the low-high operation on the odd-even operation was also observed. In the second experiment, a prime that matched the cue, mismatched it, or was neutral was presented before the cue. Results showed facilitatory and inhibitory priming effects, as well as a distance effect based on the position of a digit relative to the boundary between 5 and 6. The results of both experiments were discussed in terms of a model based on relative processing speeds of the two relevant properties of the digits.

Representation of linear orders.

Two binary classification tasks were used to explore the associative structure of linear orders. In Experiment 1, college students classified English letters as targets or nontargets, the targets being consecutive letters of the alphabet. The time to reject nontargets was a decreasing function of the distance from the target set, suggesting response interference mediated by automatic associations from the target to the nontarget letters. The way in which this interference effect depended on the placement of the boundaries between the target and nontarget sets revealed the relative strengths of individual interletter associations. In Experiment 2, students were assigned novel linear orders composed of letterlike symbols and asked to classify pairs of symbols as being adjacent or nonadjacent in the assigned sequence. Reaction time was found to be a joint function of the distance between any pair of symbols and the relative positions of those symbols within the sequence. The effects of both distance and position decreased systematically over 6 days of practice with a particular order, beginning at a level typical of unfamiliar orders and converging on a level characteristic of familiar orders such as letters and digits. These results provide an empirical unification of two previously disparate sets of findings in the literature on linear orders, those concerning familiar and unfamiliar orders, and the systematic transition between the two patterns of results suggests the gradual integration of a new associative structure.