Thomas D. Sambrook

Use of human-given cues by domestic dogs (Canis familiaris) and horses (Equus caballus)

Abstract Sixteen domestic dogs (Canis familiaris) and four horses (Equus caballus) were tested for their ability to use human-given manual and facial cues in an object-choice task. Two of the four horses used touch as a cue and one horse successfully used pointing. The performance of the dogs was considerably better, with 12 subjects able to use pointing as a cue, 4 able to use head orientation and 2 able to use eye gaze alone. Group analysis showed that the dogs performed significantly better in all experimental conditions than during control trials. Dogs were able to use pointing cues even when the cuer’s body was closer to the incorrect object. Working gundogs with specialised training used pointing more successfully than pet dogs and gundog breeds performed better than non-gundog breeds. The results of this experiment suggest that animals’ use of human given communicative signals depends on cognitive ability, the evolutionary consequences of domestication and enculturation by humans within the individual’s lifetime.

Priority of access and grooming patterns of females in a large and a small group of olive baboons

The theoretical basis of Seyfarths priority of access model of female cercopithecine grooming was critically examined and alternative models suggested. These models, named ‘engagement’, ‘interference’ and ‘rank difference’, generated different predicted grooming distributions by assuming the operation of different constraints. These constrains were, respectively, the time available for grooming, active interference on the part of higher ranked animals and a depression of grooming relations as rank difference between animals grew. These priority of access models were compared with observed grooming patterns in two groups of free-ranging olive baboons, Papio cynocephalus anubis: one large, one small. The fit of these models was poor. An alternative method of examining the effects of rank on grooming behaviour using multiple regression was successful. In the small troop the rank of the groomee explained a significant amount of the variance in grooming whilst the rank distance between groomer and groomee did not. In the large troop the opposite effect was found. In the light of these results the merits of bottom-up modelling versus top-down description are discussed. The question of group size in primates and its relationship to social complexity are addressed.

Does Visual Perspective Matter in Imitation

Theories purporting to explain the cognitive processes underlying imitation and its taxonomic distribution have proliferated in recent years but a common assumption is that imitators must adopt a models mental or visual perspective. Data on thirty-six adult subjects were used to test the hypothesis that imitative learning of knots would suffer a decrement proportional to the disparity of visual perspectives on the task that the subject held between observation and performance. There was no significant effect of visual perspective on performance, nor was there a trend in the predicted direction. This was in spite of significant preferences on the part of subjects for minimising the angle of disparity, assessed both by their behaviour and introspective report. The cognitive basis for human imitation is discussed in the light of these findings.

Vocabulary of 2-Year-Olds Learning English and an Additional Language: Norms and Effects of Linguistic Distance

Typically-developing bilingual children usually underperform relative to monolingual norms when assessed in one language only. We measured vocabulary with Communicative Development Inventories for 372 24-month-old toddlers learning British English and one Additional Language out of a diverse set of 13 (Bengali, Cantonese, Dutch, French, German, Greek, Hindi-Urdu, Italian, Mandarin, Polish, Portuguese, Spanish and Welsh). We furthered theoretical understanding of bilingual development by showing, for the first time, that linguistic distance between the child’s two languages predicts vocabulary outcome, with phonological overlap related to expressive vocabulary, and word order typology and morphological complexity related to receptive vocabulary, in the Additional Language. Our study also has crucial clinical implications: we have developed the first bilingual norms for expressive and receptive vocabulary for 24-month-olds learning British English and an Additional Language. These norms were derived from factors identified as uniquely predicting CDI vocabulary measures: the relative amount of English versus the Additional Language in child-directed input and parental overheard speech, and infant gender. The resulting UKBTAT tool was able to accurately predict the English vocabulary of an additional group of 58 bilinguals learning an Additional Language outside our target range. This offers a pragmatic method for the assessment of children in the majority language when no tool exists in the Additional Language.

Model-free and model-based reward prediction errors in EEG

Abstract Learning theorists posit two reinforcement learning systems: model‐free and model‐based. Model‐based learning incorporates knowledge about structure and contingencies in the world to assign candidate actions with an expected value. Model‐free learning is ignorant of the worlds structure; instead, actions hold a value based on prior reinforcement, with this value updated by expectancy violation in the form of a reward prediction error. Because they use such different learning mechanisms, it has been previously assumed that model‐based and model‐free learning are computationally dissociated in the brain. However, recent fMRI evidence suggests that the brain may compute reward prediction errors to both model‐free and model‐based estimates of value, signalling the possibility that these systems interact. Because of its poor temporal resolution, fMRI risks confounding reward prediction errors with other feedback‐related neural activity. In the present study, EEG was used to show the presence of both model‐based and model‐free reward prediction errors and their place in a temporal sequence of events including state prediction errors and action value updates. This demonstration of model‐based prediction errors questions a long‐held assumption that model‐free and model‐based learning are dissociated in the brain. HighlightsA reinforcement learning task was employed which permitted both model‐free and model‐based learning.A computational model was used to generate prediction error estimates for the two learning variants.Regression of model estimates against scalp voltage revealed both model‐free and model‐based prediction error activity.Traditional formal models of reinforcement learning may not accurately describe activity in the brain.

IV: RESULTS FOR STUDIES 2 AND 3: THE UKBTAT MODEL AND ITS APPLICATION TO NONTARGET ADDITIONAL LANGUAGE LEARNERS: STUDIES 2 AND 3: CHARACTERISTICS OF THE UKBTAT

This article is part of the issue “Vocabulary of 2-Year-Olds Learning English and an Additional Language: Norms and Effects of Linguistic Distance” Floccia, Sambrook, Delle Luche, Kwok, Goslin, White, Cattani, Sullivan, Abbot-Smith, Krott, Mills, Rowland, Gervain, and Plunkett (Issue Authors). For a full listing of articles in this issue, see: http://onlinelibrary.wiley.com/doi/10.1111/mono.v83.1/issuetoc.

V: GENERAL DISCUSSION.

This article is part of the issue “Vocabulary of 2-Year-Olds Learning English and an Additional Language: Norms and Effects of Linguistic Distance” Floccia, Sambrook, Delle Luche, Kwok, Goslin, White, Cattani, Sullivan, Abbot-Smith, Krott, Mills, Rowland, Gervain, and Plunkett (Issue Authors). For a full listing of articles in this issue, see: http://onlinelibrary.wiley.com/doi/10.1111/mono.v83.1/issuetoc.

Vocabulary of 2-year-olds learning English and an additional language: norms and effects of linguistic distance. II: METHODS

T HE PROCEDURE and methods used in the initial examinations of all cohorts have been described in detail (Keys et al., 1967, pp. 24-54). Except for additional items in the protocol, noted below, the same procedures and methods were used in the reexaminations five years later, and with few exceptions the same professional and assisting staff conducted the work both times. On the second as on the first occasion, the great majority of the examinations were made in the mornings before the men had indulged in any strenuous work although most of them had eaten their usual breakfast before reporting for examination. The sequence of events in the examinations started with registration by an assistant, native to or at least greatly familiar with the area and its population, who recorded any changes in family and occupational status and in personal habits, including smoking. That assistant, usually a nurse or medical technician but sometimes a physician, filled out the London School of Hygiene Cardiovascular Questionnaire (see Rose and Blackburn 1968, Annex 6). After disrobing to underwear and socks, measurements of height, weight, and thickness of the skinfolds over the triceps muscle and over the tip of the scapula were made with the same standardized methods as used in the entry examinations. Respiratory function tests, which will not be reported here, preceded the medical history and physical examinations, two internists taking alternate subjects for this latter purpose. Blood pressure was recorded at least twice at that stage. The forms for initial data, medical history, and physical examination are reproduced in the Appendix of this report. The 12-lead electrocardiogram was recorded in supine rest on multichannel machines, with routine control of calibration and paper speed (25 mm/sec). Except where there was manifest heart disease or other contraindication, a three-minute exercise test was made with repetition of the ECG