Limitations of a Bidirectional Control Procedure for the Investigation of Imitation in Rats: Odour Cues on the Manipulandum

Magazine-trained observer rats confronted a conspecific demonstrator pushing a joystick to the right or to the left for food reward before the observers were given access to the joystick from the position previously occupied by the demonstrator and rewarded for responses in both directions. For half of the observers (group 0), the joystick was in the same position when acted upon by demonstrators and observers; for the other half (group 180) the manipulandum was rotated 180 within its mounting between observation and test. As in previous experiments using this bidirectional control procedure, rats in group 0 showed demonstratorconsistent responding-that is, they pushed the joystick in the same direction, relative to the actor's body, as had their demonstrators. However, group 180 showed a reverse effect: reliable demonstrator-inconsistent responding. These results suggest that attractive odour or taste cues deposited by demonstrators on the side of the joystick contralateral to the direction of responding are sufficient to produce demonstrator-consistent responding in the bidirectional control procedure.     

Discrimination learning during the first year: stimulus and positional cues

In four studies, 3-, 6-, and 9-month-old human infants were tested in a discrimination learning task in which visual fixation to a particular stimulus or lateral position was reinforced with an auditory stimulus. In Experiment 1, all age groups exhibited acquisition, extinction, and reinstatement of fixation to the reinforced target or position. Experiment 2 revealed that 3-month-olds retained the positional discrimination but not the stimulus discrimination after a 5-min delay between acquisition and extinction; older infants retained both types of discriminations. In Experiments 3 and 4 we investigated a possible developmental shift in the dominance of positional versus stimulus cues by training infants on displays in which stimulus and position were confounded and then by dissociating the cues on test trials. Results from both experiments indicated positional cue dominance for young infants and stimulus cue dominance for older infants. The findings are discussed in terms of differences in the attentional demands elicited by proprioceptive versus exteroceptive cues.     

Experimental social innovation and client-centered job-seeking programs

The complexity of most social problems and a growing human services shortfall dictate that we reevaluate our approach to planned social change. Simplistic one-shot evaluations of social interventions are unlikely to yield the kind of information that will help us identify true social innovations, understand and refine their instrumental processes, and thereby optimize their effects. However, incremental progress in these areas is possible through the pursuit of ESI or other systematic and rigorous approaches to outcome research.     

Short- and long-term implicit memory in aging and Alzheimer's disease

Implicit memory processes were investigated via picture naming in healthy young and older adults and in persons with mild Alzheimer's disease (AD). Repetition priming in picture-naming was intact in all groups over the course of a short retention interval (seconds), and only the AD group revealed a deficit over a longer interval (72 hours). In addition, the AD group showed impaired procedural memory, with no benefit of practice on picture-naming. Impaired long-term priming was related to severity of AD. Both theoretical and methodological implications are discussed.     

Does incongruence of lexicosemantic and prosodic information cause discernible cognitive conflict?

We are often required to interpret discordant emotional signals. Whereas equivalent cognitive paradigms cause noticeable conflict via their behavioral and psychophysiological effects, the same may not necessarily be true for discordant emotions. Skin conductance responses (SCRs) and heart rates (HRs) were measured during a classic Stroop task and one in which the emotions conveyed by lexicosemantic content and prosody were congruent or incongruent. The participants’ task was to identify the emotion conveyed by lexicosemantic content or prosody. No relationship was observed between HR and congruence. SCR was higher during incongruent than during congruent conditions of the experimental task (as well as in the classic Stroop task), but no difference in SCR was observed in a comparison between congruence effects during lexicosemantic emotion identification and those during prosodic emotion identification. It is concluded that incongruence between lexicosemantic and prosodic emotion does cause notable cognitive conflict. Functional neuroanatomic implications are discussed.     

Object-centred spatial reference in 4-month-old infants

An appreciation of object-centred spatial relations involves representing a 'within-object' spatial relation across changes in the object orientation. This representational ability is important in adult object recognition [Biederman, I. (1987). Recognition-by-components: A theory of human image understanding. Psychological Review, 94, 115-147; Marr, D., & Nishihara, H. K. (1978). Representation and recognition of the spatial organisation of three-dimensional structure. Proceedings of the Royal Society of London, Series B (Biological Sciences), 200, 269-294; Tarr, M. J., & Pinker, S. (1990). When does human object recognition use a viewer-centred reference frame? Psychological Science, 1, 253-256] and is also thought to be a fundamental component of the mature object concept [Piaget, J. (1954). The Construction of Reality in the Child. Routledge & Kegan-Paul: London, UK. (Originally published in French in 1937)]. An experiment is reported in which eighteen 4-month-old infants were familiarised to a specific spatial relation within an object, across six different orientations of the object. On subsequent test trials the object was presented to the infants in an entirely novel orientation. Between successive test trials the within-object spatial relation was alternated between novel and familiar. The infants demonstrated significant sensitivity of their looking to both the novelty of the stimuli and the order in which novel and familiar stimuli were presented. It is concluded that by 4 months of age infants are able to form object-centred spatial frames of reference. These findings are discussed in the light of our current understanding of the development of object representation during infancy.