Characteristic views and the visual inspection of simple faceted and smooth objects: 'tetrahedra and potatoes'

The way in which human subjects distribute their time when attempting to learn the surface appearance of objects placed on a stand free to rotate about its vertical axis was investigated. Experiments were undertaken to establish whether observers concentrate their time on particular views and, if so, to determine the image characteristics of the preferred views. For tetrahedra, subjects concentrated on views which presented a face or an edge centred on the line of sight. Both of these views were symmetric about the vertical axis. For potatoes as examples of opaque smooth objects, subjects concentrated on four views in which the object's principal (long) axis was oriented side-on or end-on to their line of sight. For such views the horizontal width (and surface area) of the object's image had maximum and minimum values. Preferred views were not systematically related to views defined as stable from the appearance of surface boundaries or 'singularities'.     

Book reviews

Hansel, C . E. M. ESP and Parapsychology: A Critical Re-Evaluation. Buffalo: Prometheus Books. 1980. Pp. 325. Hardback 415.95; paperback £7.95. ISBN 0 87975 119 3.

Marks, D. and Kamman, R. The Psychology of the Psychic. Buffalo: Prometheus Books. 1980. Pp. 232. Hardback £16.95; paperback 48.95. ISBN 0 87975 121 5.

Atkin, R. Multidimensional Men. Harmondsworth: Penguin. 1981. £2.95. ISBN o 14 005478 2.

Frith, U. (Ed.). Cognitive Processes in Spelling. London: Academic Press. 1980. Pp. 560. £17.00. ISBN 0 12 268660 8.

Herron, J. (Ed.). Neuropsychology of Left-Handedness. Perspectives in Neurolinguistics and Psycholinguistics. London: Academic Press. 1980. Pp. xiv+357. £13.50. ISBN 0 12 343150 6.

Welford, A. T. (Ed.). Reaction Times. London: Academic Press. 1980. Pp. ix+418. £27-80. ISBN 0 12 742880 1.

Anderson, J. R. Cognitive Psychology and its Implications. San Francisco: Freeman. 1980. Pp. xviii+503. £8.10.

Bolton, N. (Ed.). Philosophical Problems in Psychology. London: Methuen. 1979. £8.50. Pp. xiii+207. ISBN 0 416 70980 X.     

Risk Factors for Attempting Suicide in Heroin Addicts

In order to examine risk factors for attempting suicide in heroin dependent patients, a group of 527 abstinent opiate dependent patients had a psychiatric interview and completed the Childhood Trauma Questionnaire. Patients who had or had never attempted suicide were compared on putative suicide risk factors. It was found that 207 of the 527 heroin abusers (39.3%) had attempted suicide. Attempters were younger; more were female, reported childhood trauma, a family history of suicidal behavior, a history of aggression, treatment with antidepressant medication, and alcohol and cocaine dependence. Logistic regression revealed that a family history of suicidal behavior, alcohol dependence, cocaine dependence, and treatment with antidepressant medication were significant predictors of attempting suicide. These results suggest that attempting suicide is common among opiate dependent patients and that both distal and proximal risk factors may play a role.