Do monkeys think in metaphors? Representations of space and time in monkeys and humans

Abstract

Research on the relationship between the representation of space and time has produced two contrasting proposals. ATOM posits that space and time are represented via a common magnitude system, suggesting a symmetrical relationship between space and time. According to metaphor theory, however, representations of time depend on representations of space asymmetrically. Previous findings in humans have supported metaphor theory. Here, we investigate the relationship between time and space in a nonverbal species, by testing whether non-human primates show space-time interactions consistent with metaphor theory or with ATOM. We tested two rhesus monkeys and 16 adult humans in a nonverbal task that assessed the influence of an irrelevant dimension (time or space) on a relevant dimension (space or time). In humans, spatial extent had a large effect on time judgments whereas time had a small effect on spatial judgments. In monkeys, both spatial and temporal manipulations showed large bi-directional effects on judgments. In contrast to humans, spatial manipulations in monkeys did not produce a larger effect on temporal judgments than the reverse. Thus, consistent with previous findings, human adults showed asymmetrical space-time interactions that were predicted by metaphor theory. In contrast, monkeys showed patterns that were more consistent with ATOM.

Figure 1

An example anchor training trial for line length (left) and duration (right). The background color of the screen indicated whether to judge line length (green background) or duration (orange background). In each case, a line was presented for a period of time, and then disappeared. Judgments were made by selecting the symbol that corresponded to either the “short” or “long” anchor (line length or duration).

Figure 2

Stimulus values for temporal and spatial cross-dimensional bisection. In the duration bisection test, participants judged seven durations (two anchors and five intermediate values) as long or short while the spatial extent of the lines were orthogonally varied between short, medium, and long values to produce 21 different duration (7 values) × spatial length (3 values) stimuli. Note that the three spatial lengths used were the short and long anchors and the geometric mean of these values. In the spatial bisection test, participants judged seven line lengths as long or short while the duration of the lines were orthogonally varied between short, medium, and long values to produce 21 different spatial (7 values) × duration length (3 values) stimuli. Note that the three durations used were the short and long anchors and the geometric mean of these values. Short and long anchors for both dimensions are indicated via bolded text above, and the geometric mean is indicated with an asterisk.

Figure 3

(A) The human bisection functions for judgments of duration when crossed with short (6 cm), medium (12 cm), and long (24 cm) spatial lengths. (B) The human bisection functions for judgments of spatial length when crossed with short (1000 ms), medium (2000 ms), and long (4000 ms) durations.

Figure 4

The monkey bisection functions for duration (WF = 0.24) and spatial length (WF = 0.19) following anchor training.

Figure 5

(A) The bisection functions (in monkeys) for judgments of duration when crossed with short (6 cm), medium (12 cm), and long (24 cm) spatial lengths. (B) The bisection functions for judgments of spatial length when crossed with short (1000 ms), medium (2000 ms), and long (4000 ms) durations. When the line was shown, the background color of the screen indicated whether to judge line length (green) or duration (orange).

Figure 6

(A) The bisection functions (in monkeys) for judgments of duration when crossed with short (6 cm), medium (12 cm), and long (24 cm) spatial lengths. (B) The bisection functions for judgments of spatial length when crossed with short (1000 ms), medium (2000 ms), and long (4000 ms) durations. When the line was shown, the background color of the screen remained light gray regardless of whether the monkeys were to judge line length or duration.