Exploration of a mouse model (C57BL/6J) capable of demonstrating behavioral changes after adolescent social isolation that are consistent with prior findings may prove beneficial in later research. This study examined 2 proposed long-term effects of isolated housing (one mouse/cage), when compared to group housing (two mice/cage) during adolescence. Mice were placed in their respective housing conditions after weaning (PND 21) and remained in those conditions until PND 60. The same cohorts were used in both phases of the experiment. Phase 1 sought to confirm previous findings that showed increases in ethanol intake after adolescent social isolation using a 2-bottle preference Drinking-in-the-Dark (DID) design over a 4-day period (PND 64-PND 67.). Phase 2 sought to elucidate the effects present after adolescent social isolation, as measured using response inhibition capabilities demonstrated during fixed-minimum interval (FMI) trials (PND 81-PND 111). Findings in phase 1 of the experiment were non-significant, save a strong tendency for female mice in both housing conditions to drink more as a proportion of their bodyweight (g/kg). However, a trend of lower bodyweight in single housed mice did exist, which does suggest that detrimental stress was applied via the used of adolescent isolation in that housing condition. Findings in phase 2 showed little effect of adolescent social isolation on mean inter-response time (IRT) at any criterion used (FMI-0, FMI-4, FMI-6). Evaluation of mean interquartile range (IQR) of IRTs showed a significantly greater amount of variation in IRT responses within single housed mice at the highest criterion (FMI-6), and a trend in the same direction when FMI-4 and FMI-6 were tested concurrently. Taken as a whole, the findings of this experiment suggest that the effect of adolescent social isolation on ethanol intake is far less robust than the effect of sex and may be difficult to replicate in a low-power study. Additionally, adolescent social isolation may interfere with the ability of mice to show consistent accuracy during FMI tasks or a delay in recognition of FMI criterion change.

Many organisms associate environmental events that occur together and can predict the outcome of the event. This ability is termed associative learning. Through associative learning, organisms are able to change their behavior to increase their fitness and survival. However, little is known about how these same learning processes proceed when subjects are not alone, but in a group. The behavior of conspecifics could serve as a cue for learning, similar to stimuli during individual learning. This study was designed to compare learning across rats exposed to a simple simultaneous discrimination task, either in an individual or a social learning setting. Sixteen rats were trained to choose between two corridors differentiated by visual stimuli (flashing or steady light). One of the two cues signaled that food was available in the feeders at the end of the corridor. Half of the rats were trained individually and the other half were trained in groups of four. To compare the effect of the social training setting, all rats were tested independently and in a group. Next, contingencies were reversed and the previously non-reinforced cue now signaled the availability of food, and rats were again tested individually and in a group. The results suggest that the social setting interferes with the rats’ ability to make associations but makes the performance of the rats less sensitive to changes in their learning environment.