Perceived variability and symbol use: a common language-cognition interface in children and chimpanzees (Pan troglodytes)

Analysis of two chimpanzees' conversations with their teacher during a tool-use training task demonstrated that chimps use lexigrams, a humanly devised visual symbol system, selectively to encode perceived variability; that is, they generally used their symbols to differentiate alternative possibilities or to represent change or novelty in a situation. In contrast, they tended to leave unsaid what was unchanging, repetitive, or the unique possibility in a situation. Perceived variability influenced not only which symbols were selected but also utterance length: A single dimension of variability in a situation leads to single-lexigram utterances; multiple dimensions are associated with multi-lexigram utterances. This pattern of results indicates that the absence of formal grammatical structure in chimp language does not imply that utterances beyond one word in length are either rote strings or imitations. The chimps' tendency to mention the variable while leaving the constant or redundant unsaid is, moreover, strong support for the position that their use of a humanly devised symbol system is more than a series of conditioned responses.     

Follow-up of a full-scale network assembly

The authors conducted two full-scale network assemblies for the family network of a suicidal adolescent. Findings from the clinical follow-up and telephone interviews with 21 of 65 participants revealed benefits for the index family and the network members who participated in the meetings. A ripple effect in which the participants' own personal networks improved was also demonstrated. Benefits included resolution of a suicidal crisis, better understanding of depression and family stress, more adaptive responses to depression and suicidal risk, and improved personal relationships. No casualties from this intervention were discovered. This report is intended to stimulate future, more systematic outcome studies.     

Mechanisms of blocking by contextual stimuli

The influence of contextual stimuli on the conditioning and performance of responding to a discrete stimulus was examined in the US preexposure paradigm using both context shift manipulations and a measure of context conditioning. Four groups of rats received both repeated exposure to an electric shock US in one context (Context 1), and repeated nonshocked exposure to a second context (Context 2). Two additional groups of rats received exposure to these contexts, but never received shock presentations. Rats exposed to shock learned to escape from the stimuli of Context 1, but did not escape from the stimuli provided by Context 2. Rats not exposed to shock failed to escape from either context. All rats then received a single CER conditioning session in which four pairings of a 3-min noise CS and shock US were presented. Half the rats received those CS-US pairings in the excitatory Context 1, while the remaining rats received those pairings in the neutral Context 2. Finally, half the rats in each of the CER conditioning treatments received extinction test trials of the noise CS in Context 1, while the remaining rats received those test trials in Context 2. Thus, this design factorially manipulated the presence of excitatory or neutral contextual stimuli during both conditioning and testing of a discrete CS. In comparison with the two groups of rats never preexposed to shock alone, attenuation in acquisition of conditioned suppression observed during test trials occurred only when CER conditioning had been administered in the excitatory Context 1, and this effect was manifested when testing occurred in either the excitatory Context 1 or the neutral Context 2. These results support the model of R. A. Rescorla and A. R. Wagner (1972) (in A. H. Black & W. F. Prokasy (Eds.) Classical Conditioning II, pp. 64–99, New York: Appleton-Century-Crofts) which asserts that contextual stimuli and sicrete CSs compete for limited associative strength supportable by a given US.     

Arousal and T-maze choice behavior in mice: A convergent paradigm for neophobia constructs and optimal arousal theory

Three experiments investigating the effects of arousal on the T-maze choice behavior of inbred mouse strains are reported. In Experiment 1, CBA and NZB mice were administered unrewarded free choice alternation tests on 10 consecutive days under either No Shock, Shock Start (shocked in the start box), or Shock Choice (shocked at the choice point) treatment conditions. Both strain and treatment effects were observed: In the No-Shock condition, the nonreactive CBA strain alternated, but the reactive NZB strain did not. In the Shock Start condition the CBA strain showed only a suppressed alternation, while the NZB strain administered the same treatment perseverated. Both strains perseverated in the Shock Choice condition. In Experiment 2, NZB mice administered identical shocks in the start box and goal arms on both trials of five consecutive tests conducted once a day perseverated to the same goal arm in which they had been shocked on the first trial. In Experiment 3, NZB mice punished for perseverating (with shock continuation) and simultaneously reinforced for alternating (with shock termination) showed a “punishment paradox”; they perseverated despite the reinforcement contingencies. These results, which are congruent with the optimal arousal theory and several characteristics the theory shares with the emergent neophobia construct, support the contention that arousal mediates a symmetrical relationship between approach and avoidance along a novelty-familiarity continuum.