Maree Hunt

The cage preferences of laboratory rats

Preference tests were used to assess a range of enrichment options for rats kept under standard New Zealand (and similar) caging conditions. The rats did not show significant preferences for most of the options, over an empty cage. The exceptions were shredded paper, a nesting box and a semi-enriched condition incorporating a range of modifications. These cage modifications are recommended for the enrichment of laboratory rats.

(+/-)3,4-methylenedioxymethamphetamine, d-amphetamine, and cocaine impair delayed matching-to-sample performance by an increase in susceptibility to proactive interference.

This study compared the effects of (+/-)3,4-methylenedioxymethamphetamine, d-amphetamine, and cocaine on performance of rats in a delayed matching-to-sample procedure using a variety of indices of performance to determine the mechanism by which working memory task impairments arise. All 3 drugs produced an overall delay-independent decrease in accuracy rather than a delay-dependent increase in the rate of forgetting. This impairment arose as a result of current-trial choice responses being progressively more affected by responses made in the immediately preceding trial as drug dose increased. Therefore, all 3 drugs produced qualitatively similar disruptions in memory task performance best characterized as an impairment arising from proactive sources of interference.

Differential effects of MDMA and scopolamine on working versus reference memory in the radial arm maze task

Previous research has suggested that the disruption to memory-task performance seen following acute exposure to 3,4-methylenedioxymethaphemtamine (MDMA) with rats might best be characterized as reference memory impairment rather than a working memory impairment. The current study specifically compared the effects of MDMA and scopolamine on measures of working versus reference memory in an eight-arm radial maze task. It was predicted that scopolamine would produce a greater impairment with respect to the working memory component of the task, whereas MDMA would produce a greater impairment to reference memory. On each trial rats were allowed to make a total of four arm visits in order to collect the reinforcers located at the end of different arms in the maze. Working memory errors were indicated by re-visiting an already visited arm during a trial, whereas visiting an arm that was never baited on any trial indicated a reference memory error. Using a within subjects design, rats were exposed to a range of doses of scopolamine and MDMA administered acutely. An interaction between drug type and memory error type was found. Specifically, scopolamine produced more working memory errors than reference memory errors, while MDMA produced the opposite pattern of significantly more reference memory errors compared to working memory error. This finding supported the hypothesis that MDMA disrupts reference memory processes in terms of an impairment in the strategies or rules used for solving memory tasks.

An Animal Model of Slot Machine Gambling: The Effect of Structural Characteristics on Response Latency and Persistence

Despite the prevalence of problem gamblers and the ethical issues involved in studying gambling behavior with humans, few animal models of gambling have been developed. When designing an animal model it is necessary to determine if behavior in the paradigm is similar to human gambling. In human studies, response latencies following winning trials and near win trials are greater than those following clear losses. Weatherly and Derenne (Anal Gambl Behav 1:79–89, 2007) investigated whether this pattern was found with rats working in an animal analogue of slot machine gambling. They found a similar pattern of response latencies but the subjects’ behavior did not come under control of the visual stimuli signalling the different outcomes. The animal model of slot machine gambling we used addressed procedural issues in Weatherly and Derenne’s model and examined whether reinforcer magnitude and the presence of near win trials influenced response latency and resistance to extinction. Response latencies of the six female Norway Hooded rats varied as a function of reinforcer magnitude and the presence of near-win trials. These results are consistent with prior research and with the idea that near win trials serve as conditional reinforcers.

Imagination inflation is a fact, not an artifact: A reply to Pezdek and Eddy

Pezdek and Eddy (2001) claim to prove that imagination inflation is a spurious effect caused by regression to the mean (RTM). They make four predictions about what patterns of data would demonstrate a genuine effect for imagination versus those that would be explainable by RTM. We review each of those predictions, and demonstrate significant problems with them. We conclude that imagination inflation is a genuine effect, and that Pezdek and Eddy’s work has contributed to the growing research showing that when people imagine fictitious events from long ago, they become more confident that those false events were genuine experiences.

Modifying driver behaviour with passenger feedback

A feedback programme was employed to help drivers improve their safety behaviour based on the idea that particular types of driver error result from contingency traps as defined by Fuller [Journal of Applied Behaviour Analysis, 24 (1991) 73]. Two drivers and their single respective passengers participated. For each driver, repeated in-car observations were made of four unsafe driving behaviours. Two of these were sequentially targeted in the behavioural intervention that involved the passengers providing informational feedback to their driver. Both drivers showed a marked improvement across the targeted behaviours. The study demonstrated the applicability of behaviour analysis to the traffic domain and the efficacy of individual feedback as a behavioural tool for positive behaviour modification.

Short communication: rat's demand for group size.

Social isolation compromises the welfare of rats. However, it is not clear how many rats should be housed together under laboratory conditions. Pair housing, sometimes recommended over group housing, may help avoid aggression and disease transmission. Female rats, however, showed the highest average demand for a group size of 6 (versus 1, 2, 4, and 12) when stocking density was maintained at 20 cm2/rat. This finding contributes to work suggesting that rats should be group housed. This article shows that further studies are required into the actual risks of disease and injury associated with group versus pair housing.

The "negative" credit card effect: Credit cards as spending-limiting stimuli in New Zealand.

The “credit card effect” describes a finding where greater value is given to consumer items if credit card logos are present. One explanation for the effect is that credit cards elicit spending behavior through associative learning. If this is true, social, economic and historical contexts should alter this effect. In Experiment 1, Year 1 New Zealand university students valued consumer items less in the presence of credit card logos. Experiment 2 replicated this effect. These findings support the idea that New Zealand students” negative conditioning history with credit card stimuli results in a “negative” credit card effect, whereby credit cards limit rather than facilitate spending. This “negative” effect suggests that the presence or absence of a “positive” effect in previous studies depends on previous associations with credit card stimuli

Human performance on a two-alternative rapid-acquisition choice task

Davison and Baum [Davison, M., Baum, W. M., 2000. Choice in a variable environment: every reinforcer counts. Journal of the Experimental Analysis of Behavior 74, 1-24.] developed a concurrent-schedule procedure where, within each session, different reinforcer ratios were arranged across components separated by brief black-outs. Behaviour adapted quickly to the reinforcer ratios and reinforcers also had local effects on responding. This procedure has been used with pigeons and rats. In the present experiment, we adapted the Davison and Baum procedure to study the effects of reinforcement on human choice behaviour. Eighteen participants were presented with four different reinforcer ratios within a single 50-minute session. Mean sensitivity to the reinforcer ratios increased within components, and preference was greater for the just-reinforced response alternative immediately following reinforcer delivery, similar to the results from non-human experiments. Although there were limitations to the current procedure, the local time scale analyses are a novel way of examining human operant behaviour.

Set-size and Frequency-of-occurrence Judgements in Young and Older Adults: The Role of the Availability Heuristic

Two experiments examined the cognitive processes underlying judgements of set size and judgements of frequency of occurrence in young (Experiments 1 and 2) and older (Experiment 2) adults. Previous research has implicated the availability heuristic in set-size judgements, whereas an automatic processing mechanism has been implicated in judgements of frequency of occurrence. In the current experiments, path analysis was employed to investigate the role of an availability bias in performance on the judgement tasks. In Experiments 1 and 2, both types of judgement were influenced by repetition frequency of words independent of the availability (recall) of specific exemplars. Experiment 2 extended the investigation to include age differences. Although older adults’ recall performance was poorer overall, the availability bias was age invariant, and there were no age differences in either set-size or frequency-of-occurrence judgements. Our results indicate that both set-size and frequency-of-occurrence judgements are independent of the availability bias evident in recall, and they support the notion that an automatic processing mechanism underlies both types of judgement.