Mitchell M. Metzger

The world wide web and the laboratory: a comparison using face recognition.

In recent years, a growing number of psychological researchers have turned to the World Wide Web (WWW) as a resource to access participants in experimental studies. While there are benefits to this approach in conducting psychological research (e.g., access to a potentially large subject pool and faster data collection), there are also concerns regarding this medium (e.g., the validity of the data). In recent years, data collected on-line has been validated by comparing it to data collected in the traditional laboratory setting. This study attempted to build on these previous reports by comparing face recognition data collected on the web and data collected in a laboratory. In two separate experiments, data collected from WWW participants did not statistically differ from data collected with undergraduate college students in a classroom setting. These findings strongly suggest that the WWW may be a viable alternative for researchers conducting face recognition experiments.

Stress-induced memory enhancement for inhibitory fear conditioning in rats

The retroactive effects of stress on memory have not received a great deal of empirical attention; however, the research that has been conducted has reported both positive and negative effects of stress on memorial processes. The goal of this study was to examine the effects of a naturalistic Stressor—an intense bout of exercise—on memory for inhibitory fear conditioning in rats. Experiment 1 investigated the retroactive effect of a stressful swim treatment on memory for passive avoidance (PA) training. Rats that received an immediate posttraining swim treatment demonstrated a significant enhancement in performance when tested for retention 24 h later. Furthermore, the enhancing effect of the swim treatment was time dependent: Rats receiving the swim treatment 15 min after PA training no longer exhibited reliably better scores than did rats not receiving the swim treatment. Experiment 2 used preexposures to control for the possibility that the swim treatment was enhancing avoidance scores by acting as a punisher rather than a memory modulator. Results indicate that both the group that was preexposed and the group that was not preexposed showed reliably higher scores than did a group of animals receiving only PA training, thus replicating Experiment 1. Furthermore, the results of Experiment 2 suggest that swimming was not simply acting as a punishing agent, since preexposures to the treatment did not attenuate its memory-enhancing properties. The possible role of stress-related hormones on memory processes is considered.

Is Acquired Tolerance to Hypothermia Susceptible to Extinction

Studies examining adaptation to thermoregulatory challenges have shown that tolerance to hypothermia is mediated, in part, by associative (Pavlovian) learning mechanisms. This study examined whether acquired tolerance to deep body cooling (hypothermia) could be extinguished by conditions in which presentations of the environmental cues were presented in the absence of hypothermia treatment. The results of Experiment 1 indicate that five extinction exposures in which the context was presented alone were not sufficient to extinguish established hypothermia tolerance in rats. Experiment 2 demonstrated that tripling the number of daily extinction exposures from 5 to 15 also did not disrupt adaptation to cold, and further demonstrated that the presentation of a challenge condition (heat exposure) over the 15-day extinction phase of the experiment had no effect on established cold tolerance. Furthermore, Experiment 2 confirmed associative control of tolerance by demonstrating a context shift effect in resistance to cold. The lack of an extinction effect in these two experiments suggests that the environmental context may be acting as an occasion setter.

The forgetting of stimulus attributes in latent inhibition

Numerous studies have demonstrated that the forgetting of stimulus attributes is a common occurrence; that is, organisms forget the specific characteristics of training stimuli over long retention intervals, while retaining general information of the training stimuli themselves. However, most studies have examined this effect after a learning episode, and there have been virtually no accounts to test whether the forgetting of attributes occurs for stimuli presented prior to training. Therefore, this experiment was designed to test that possibility, and it examined whether the forgetting of stimulus attributes occurred prior to training for the flavor stimulus in a conditioned taste aversion (CTA) procedure. Specifically, a latent inhibition (LI) procedure was used to measure the extent of forgetting for a pre-exposed flavor over short and long retention intervals. The results indicate that rats forgot the specific characteristics of the flavor stimulus (CS) while retaining memory for pre-exposure sessions over a long retention interval. That is, subjects pre-exposed and conditioned with different concentrations of sucrose showed no LI effect with a 1-day delay between pre-exposure and training, but demonstrated a generalized LI with an 8-day delay between pre-exposure and conditioning. This experiment provides further evidence for the robustness of the forgetting of stimulus attributes, and demonstrates that this specific type of forgetting also occurs prior to the learning of a CTA task.

Directed Forgetting: Differential Effects on Typical and Distinctive Faces

ABSTRACT Directed forgetting (DF) occurs when stimuli presented during the study phase are followed by “forget” and “remember” cues. On a subsequent memory test, poor memory is observed for stimuli followed by the forget cues, compared to stimuli followed by the remember cues. Although DF is most commonly observed with verbal tasks, the present study extended intentional forgetting research for nonverbal stimuli and examined whether faces were susceptible to DF. Results confirmed that the presentation of a forget cue significantly reduced recognition for faces, as compared to faces followed by a remember cue. Additionally, a well-established finding in face recognition is that distinctive faces are better remembered than typical faces, and Experiment 2 assessed whether face appearance influenced the degree of DF. Results indicate that the DF effect observed in Experiment 1 was replicated in Experiment 2 and that the effect was more pronounced for those faces that were typical in appearance.

Spectacles, distinctiveness, and face recognition: a web-based experiment.

This study sought to clarify previous research in the face recognition literature regarding memory for faces with spectacles. A second aim of this research was to further investigate Valentines face-space model, a leading model of face recognition that predicts better performance on distinctive faces compared to typical faces. Prior to this experiment, independent observers provided distinctiveness ratings for faces with, and without, spectacles. Experimental participants then accessed the PsychExperiments website and completed a face recognition experiment. Based on the judgments of the independent observers, the face-space model predicts that memory for spectacled faces should be superior to memory for non-spectacled faces. An analysis of hit rate (percent correct) supported this notion, as a higher hit rate was observed for spectacled faces compared to non-spectacled faces. However, the analysis of false alarms (false identifications) did not support the predictions made by the face-space model, as participants demonstrated reliably higher false alarm rates for faces with spectacles. A further analysis of response bias suggests that the overall pattern of responding may have been largely due to changes in response criteria for trials where spectacled faces were presented. Implications for models of face recognition are discussed.

Differential Effects of Ketaset/Rompun Anesthesia on Hypothermia-Induced Retrograde Amnesia and Its Recovery

A nonbarbiturate anesthetic consisting of ketamine HCl (Ketaset) and xlyazine (Rompun) was administered to assess the effects of anesthesia on hypothermia-induced retrograde amnesia in Long Evans hooded and Sprague-Dawley albino rats. Results from Experiment 1a indicate that this anesthetic does not attenuate retrograde amnesia, and the findings from Experiment 1b suggest that awakening from Ketaset/Rompun anesthesia at normal body temperature (following administration of deep body cooling) does not attenuate the resulting hypothermia-induced retrograde amnesia. Experiment 2 demonstrated that various delays between training and hypothermia resulted in a temporal gradient that was the same for animals cooled while either conscious or under anesthesia. The results of Experiment 3 showed that rats made amnesic while under anesthesia did not recover the target memory if given a recooling treatment, but rats that were made amnesic while conscious did recover the memory with the same reminder treatment. These findings indicate that the conscious processing of stimuli associated with hypothermia treatment is not necessary in inducing hypothermia-induced retrograde amnesia, but that conscious processing is an important factor if the amnesia is to be recovered with a recooling treatment.

Ketaset-Rompun Anesthesia Induces a Conditioned Taste Aversion in Rats

Two experiments paired a novel sucrose solution (conditioned stimulus, or CS) with injections of Ketaset-Rompun anesthesia (unconditioned stimulus, or US) to examine the effects of this anesthetic on the development of conditioned taste aversions (CTA) in Sprague-Dawley rats. Experiment 1 showed that using Ketaset-Rompun anesthesia as the US produced a reliable taste aversion, as rats injected with the anesthetic immediately after consumption of a novel sucrose solution drank significantly less sucrose on a 24-hr retention test compared to rats injected with an equivalent volume of saline at training. Additionally, Experiment 2 demonstrated that the level of Ketaset-Rompun-induced CTA varied with the CS-US interval. In this experiment, rats injected with the anesthetic demonstrated an aversion to sucrose at testing if the presentation of the CS was followed by injections of the US either immediately, 1 hr, or 2 hr later. However, when the US was administered 4 or 6 hr after presentation of the CS, no aversion to sucrose was manifested at testing. Furthermore, the results of Experiment 2 suggest that the largest CTA was obtained with the 2-hr delay condition. The methodological implications for researchers using Ketaset-Rompun for surgical interventions is considered.

Adaptation to exercise in the rat: Lack of associative control

A procedure in which female Long-Evans rats were swum to a criterion of fatigue was utilized to assess the contextual determinants of adaptation to exercise. In Experiment 1, it was observed that rats given four exercise exposures demonstrated significant adaptation to the treatment, as indicated by reliably longer swimming times over the course of exercise exposure. Furthermore, the change in swimming times reflected in these subjects was not due to maturation or growth over the course of the experiment, as their body weights before and after the experiment did not reliably differ. Experiment 2 addressed whether adaptation to swimming exercise was susceptible to a context shift effect, as is tolerance to drugs and adaptation to other homeostatic disturbances (e.g., hypothermia). Using a within-subject design, Experiment 2 demonstrated that a shift in contextual stimuli (a procedure that reliably disrupts drug tolerance and hypothermia adaptation) failed to disrupt established adjustment to exercise. The results of these experiments suggest that adaptation to exercise may be mediated by different mechanisms than adaptation to other disturbances (e.g., drugs, hypothermia), since an alteration in contextual stimuli did not appear to be detrimental to established exercise adaptation with this paradigm.