Discrimination of five-dimensional stimuli by pigeons: Limitations of feature analysis

Pigeons were trained to discriminate between stimuli constructed using five orthogonal two-valued features. The stimuli consisted of stylized monochrome drawings of seeds. Two different training procedures (conditional and simultaneous discrimination) were used. In the first two experiments, the discrimination required was between polymorphous categories, in which a positive stimulus was defined as one in which three or more of the five features took their positive values. Discrimination in both experiments was imperfect; the pigeons' behaviour only came under the control of a subset of the available features (one to three in Experiment 1, three or four in Experiment 2). In Experiment 3, single features had to be discriminated, while the remaining features varied. It was found that all five features of the “seed” stimuli could be discriminated, but one of them was exceptionally difficult. The results show that pigeons do not reliably use all the features available to them when making category discriminations. This casts doubts on feature analysis as a basis for the excellent performance pigeons show when required to discriminate between categories of natural objects.     

Tourette's syndrome—case report and contribution to the Prata/Masson-Nunn controversy

The conflicting views on Tourette's syndrome (TS) and its management in children put forward in the November 1985 issue of Journal of Family Therapy (Nunn, 1985; Prata & Masson, 1985) and the Editorial in the same issue prompt us to report a case. A twelve-year-old boy with TS managed on interactional lines snowed changes more modest than those achieved by Prata and Masson, and we address some of the issues raised by Nunn in his critique of their paper.     

Thoughts of Self‐Harm and Help‐Seeking Behavior among Youth in the Community

The association between thoughts of self‐harm and help‐seeking among youth with symptoms of depression was examined. Data were drawn from the Health Behavior of School‐aged Children Study (n = 15, 686), a nationally representative sample of youth in the United States. Analyses focused on comparing help‐seeking behaviors among youth with and without thoughts of deliberate self‐harm (DSH) when depressed. Depressed youth with thoughts of DSH exhibited different patterns of help‐seeking than those without. Both groups most frequently sought help from friends and parents. However, adolescents with thoughts of DSH were statistically more likely than youth without to seek help from friends (DSH: 69.9%; no DSH: 57.8%; AOR = 1.46), but less likely to seek help from parents (DSH: 53.7%; no DSH: 73.1%; AOR = 0.47). Youth with DSH were more likely to seek help from school officials (AOR = 1.05), health professionals (AOR: 1.83), or a counselor (AOR = 1.93) compared with those without thoughts of DSH who were more likely to seek help from a sibling (AOR: 0.77) or other relatives (AOR: 0.78). Results may help inform programs to improve identification of youth at risk of self‐harm in community and school settings.     

The priming of word associations: A levels-of-processing approach

Four experiments are reported in which the magnitude of the associative-priming effect is manipulated by varying both the experimental task and the conditions within a given task. The between-task manipulation involved a comparison of priming effects in length categorization on the one hand and lexical decision on the other. The within-task manipulation involved varying the type of letter strings presented as the nonword stimuli in lexical decisions. Pseudowords and two types of orthographically illegal letter strings—namely, consonant strings and random letter strings—served as nonwords. Finally, the effect of varying the proportion of pseudowords to illegal nonwords across four sets of experimental materials was investigated. On the whole, these within-and between-task manipulations turned out to be very effective ways of affecting the size of the associative-priming effect. Also, the size of the lexicality effect (the difference between the RTs to word and nonword stimuli) varied systematically with these within-and between-task manipulations. The results are discussed in relation to both Shulman and Davison's (1977) parallel-processing model and Balota and Chumbley's (1984) account of lexical decision.