Measuring clustering differences among categories in the same list

A method is presented for analysis of clustering differences among categories in the same list. This allows category characteristics to be varied within Ss by using mixed lists, whereas previously only homogeneous lists could be employed.     

Local and Global Sources of Control in Pigeon Delayed Matching-to-sample Performance

The present study employed a behavioural detection approach to investigate the combined effects of sample duration and sample presentation frequency on delayed matching accuracy of pigeons. Experiment 1 showed that when both samples were exposed at each of the two possible durations within a two-alternative, delayed matching session, discriminability was higher to the longer duration sample than to the short-duration sample, as found when sample duration is varied between sessions. Experiment 2's asymmetrical procedure increased bias toward the more frequent of the two samples but had no influence on discriminability. Initial discriminability was higher to samples exposed for longer durations, irrespective of stimulus presentation frequency. The results suggest qualitatively different effects of the two sources of stimulus control under consideration: Sample duration (a local or within-trial manipulation) exerted its effect on discrimination of the stimuli, whereas sample presentation frequence (a global factor) exerted its major effect on response bias. An interpretation of the data in terms of Blough's (1996) analysis of errors in matching tasks suggests that the amount of behaviour under control of the sample stimulus markedly changed with different sample durations. The analysis also showed that the biasing manipulation exerted most of its effect on the portion of behaviour outside of control by the critical stimulus. We argue that theoretical accounts of delayed matching performance need to consider both local and global factors as determinants of matching accuracy.     

Nonresident Suicides in England: A National Study

Little is known about the numbers and characteristics of people who travel away from home before dying by suicide. Therefore, this studied attempts to identify the sociodemographic characteristics, location, and method of suicide in people who died distant from home, in a national sample. Data were collected on all English suicides and a patient population; nonresident suicides resided in one Health Authority but died in a different one. Twelve percent of suicides were nonresident and features of these included: young age, social adversity, and severe mental illness. In conclusion, both individual‐ and area‐based factors are likely to contribute to suicide away from home.