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These introductory comments for the special issue on Pavlovian conditioning begin with a brief review of Rescorla’s (1988) influential paper outlining how trends in the study of Pavlovian conditioning changed the dominant view from an analysis of simple associations to an information seeking approach. I argue that current research trends in Pavlovian conditioning suggest possible ways of integrating the information-seeking approach with a more embodied, evolutionary approach. I briefly consider four trends reflected in the following papers that potentially add to our appreciation of how ecology and evolution are involved in conditioning: (1) Exploring an adaptive basis for Pavlovian conditioning; (2) Clarifying the relation of Pavlovian and operant conditioning; (3) Relating preexposure and sensory preconditioning to the organization of exposure learning; and, (4) Integrating models of Pavlovian conditioning.

In two experiments we investigated the extent to which rats (Rattus norvegicus) use an egocentric trajectory and landmarks to locate a goal. In Experiment 1 we trained groups to locate the hidden platform in a water maze with either 1 of 3 or 3 of 3 predictive landmarks, and with either a random or fixed egocentric trajectory. A choice test revealed that regardless of the landmark configuration, rats relied on a directional, egocentric trajectory, when it was available, to locate the platform. In Experiment 2 we found that adding four predictive landmarks following training with a constant egocentric trajectory did not alter rats' initial attention to the trajectory. We conclude that the presence of nonpredictive landmarks in a predictive array did not affect the use of landmarks. With a blocking design, rats used initially an egocentric path, then landmarks. These results add to the notion that animals use available spatial cues sequentially. Keywords: egocentric, allocentric, spatial behavior, water maze, rat DOI: 10.1037/a0019458

In Stage 1 of 4 experiments in which rats completed a water-maze blocking procedure, experimental groups were trained to use a predictive beacon (hanging above, connected to, or displaced from the platform) to find a submerged escape platform in the presence of predictive or irrelevant background cues and in the presence or absence of irrelevant landmarks. In Stage 2, a fixed beacon, landmarks, and background cues all predicted the platform location. A Room Test (landmarks and background cues only) showed that Stage 1 training with a fixed hanging beacon or the moving displaced beacon facilitated Stage 2 learning of predictive room cues for experimental relative to control subjects. In contrast, Stage 1 training with a moving pole beacon interfered with Stage 2 learning about predictive room cues relative to controls, whereas training with a fixed pole or moving hanging beacon had no effect. We conclude that multiple spatial learning processes influence locating an escape platform in the water maze. Keywords: spatial learning, water maze, locale learning, facilitation, cue competition

James A. Dinsmoor, writer and social activist, believed in a mantra called 'never stop asking questions' which is one of the characteristics of any scientist, but he systematically and persistently committed himself to this mantra. He was influential in supporting scholarly and applied communities in experimental psychology and behavior analysis.

Issues related to backward excitatory conditioning are examined. One group of rats was exposed to light that followed food, another group to light that preceded food, and a third group to compound conditioning. A behavior system was used to predict food search habits.

The temporal pattern of stimuli in an interfood clock affected rats' behavior during intervals between feedings. When duration cues were progressively longer, activity near the feeder was increased at the beginning of the interfood interval. Progressively shorter cues were associated with increased locomotion in the middle of the interfood interval and more feeder-related responses near the end.

Backward serial conditioned stimuli can control a set of post-food searching behaviors that can influence later pre-food searches. Rats first trained with a backward conditioned stimulus (CS) with proximity to food were then trained with a different CS element. Temporal proximity to food was found to affect the outcome of these experiments.

A physical map of the 31-megabase Aspergillus nidulans genome is reported, in which 94% of 5,134 cosmids are assigned to 49 contiguous segments. The physical map is the result of a two-way ordering process, in which clones and probes were ordered simultaneously on a binary DNA/DNA hybridization matrix. Compression by elimination of redundant clones resulted in a minimal map, which is a chromosome walk. Repetitive DNA is nonrandomly dispersed in the A. nidulans genome, reminiscent of heterochromatic banding patterns of higher eukaryotes. We hypothesize gene clusters may arise by horizontal transfer and spread by transposition to explain the nonrandom pattern of repeats along chromosomes.