Exploratory behavior: The inadequacy of activity measures

Abstract

It has been reported that rats show lower activity and alternation scores in an elevated maze than they do in an enclosed maze, -and it has been argued that this can be explained by a theory relating exploration to anxiety. But it is shown here that behavior in the two kinds of maze is so different that these comparisons do not justify the conclusions drawn from them. Lester (1967a) has compared the locomotor activity of rats in an elevated and an enclosed Y maze of similar dimensions and reported two differences. Rats in the elevated maze moved less often from one maze arm to another. They also showed a lower level of alternation between arms at the first opportunity: that is to say, having been placed in one arm (A), and having entered a second arm (B), they were less likely than rats in the enclosed maze to make their next entry into the third arm (C). Lester takes these results as supporting a theory of exploratory behavior (Lester, 1967b) according to which the probability of a rat's approaching a stimulus in its environment fIrst increases and then decreases as a function of the fear aroused by that stimulus. The fear aroused by a stimulus is held to depend partly on its novelty, and partly on the rat's basal level of fear.If this theory is to explain Lester's results, a number of assumptions have to be made. It must be assumed that rats in an elevated maze are generally more fearful than rats in an enclosed maze. Lester provides no independent evidence for this, but Halliday (1967) has recently reported that rats defecated more in an elevated maze. It must also be assumed that the measure Lester took of locomotor activity (the number of occasions on which a rat moved from one maze arm to another) is a measure of the rat's exploratory approaches to the stimuli in its environment, and further that it is an equally appropriate measure in both kinds of maze. But before we are justifIed in making this last assumption (and concluding, as Lester's theory predicts, that rats in elevated mazes explore less) we need to examine the behavior more carefully. An elevated and an enclosed maze may have identical ground plans, but they necessarily present the rat with very different sensory environments. In particular, of course, extramaze cues are likely to be far more prominent with an elevated maze. It may be, therefore, that there will be gross differences in behavior in the two situations, and that different patterns of response may have a claim to be called exploratory. If this proved to be so, comparisons based simply on Lester's measure of locomotor activity would obviously be unsatisfactory. 38The following results (extracted from a longer experiment with rats in an elevated maze) seem to be relevant.Method. The Ss were 18 hooded female rats, without previous maze experience, and about 100 days old. Each rat was observed for 3 min on each of three successive days in a wooden elevated Y maze. The arms, measuring 18 x 4 in. were set at angles of 120 deg to each other. The maze was supported 18 in. above the floor w...

The relationship between fear and exploration in rats

“…We do not know the limits of the rat's perception. Sheldon (1968) has noted that the rat on an elevated maze spends much time with his head over the arm of the maze, but this may result from the absence of a wall to confine the rat rather than visual exploration of the environment.…”

Nociceptin/Orphanin FQ Increases Anxiety-Related Behavior and Circulating Levels of Corticosterone During Neophobic Tests of Anxiety

“…Unfortunately, thigmotactic responses were not assessed in that experiment. Since thigmotactic behaviors are thought to reflect anxiety states more reliably than locomotor counts do (Sheldon, 1968;Archer, 1973;File, 1985), it would be interesting to evaluate the potential effect of N/OFQ on urocortin-or FG 7142-induced alterations in thigmotaxis.…”

Can Social Interaction Be Used to Measure Anxiety?

“…As well as scoring social interaction, each observer scored the time one rat spent exploring. Because motor activity has been so frequently criticised as a measure of exploration (Sheldon, 1968;Archer, 1973;Robbins & Iversen, 1973;File & Wardill, 1975) it is essential to use a measure of directed exploration. In this part of the experiment, therefore, objects were hung on the walls of the box and exploration was measured by the time spent sniffing and manipulating objects.…”