The temporal dependence of exploration on neotic style in birds

Abstract

Exploration (interacting with objects to gain information) and neophobia (avoiding novelty) are considered independent traits shaped by the socio-ecology of a given species. However, in the literature it is often assumed that neophobia inhibits exploration. Here, we investigate how different approaches to novelty (fast or slow) determine the time at which exploration is likely to occur across a number of species. We presented four corvid and five parrot species with a touchscreen discrimination task in which novel stimuli were occasionally interspersed within the familiar training stimuli. We investigated the likelihood that an animal would choose novelty at different stages of its training and found evidence for a shift in the pattern of exploration, depending on neotic style. The findings suggest that faster approaching individuals explored earlier, whilst animals with long initial approach latencies showed similar amounts of exploration but did so later in training. Age rather than species might have influenced the amount of total exploration, with juveniles exploring more than adults. Neotic style varied consistently only for one species and seems to involve a strong individual component, rather than being a purely species-specific trait. This suggests that variation in behavioural phenotypes within a species may be adaptive.

Figure 1

Theoretical model illustrating the shift in exploration-probability dependent on neotic style; solid- and perforated black lines indicate assumed responses to baseline stimuli (S+ and S−) throughout the course of learning; coloured lines represent proposed total novelty response probability for individuals approaching novelty fast or slow over time, with assumed normal distribution, if novel stimuli are non-rewarded; shaded areas denote corrected total novelty responses; hence, we assume the total amount of corrected novelty responses (shaded area) as well as the height of the peak to be dependent on how explorative an individual is and its general learning capacity, whereas the location of the peak on the time axis to be defined by what neotic style an individual pursues.

Figure 2

Delta latencies (approach latency in the last, non-consecutive session subtracted from the approach time in the first trial of session one) for all species; bold horizontal lines indicate median values, boxes span the first to third quartiles and whiskers represent 95% confidence intervals; horizontal lines indicate species comparisons; Significance codes: ‘***’ for p < 0.001, ‘**’ for p < 0.01, ‘*’ for p < 0.05, ‘t’ for p < 0.1 (alpha adjusted for multiple comparisons).

Figure 3

Age differences in corrected novelty responses; bold horizontal lines indicate median values, boxes span the first to third quartiles and whiskers represent 95% confidence intervals; horizontal lines indicate species comparisons; Significance codes: ‘***’ for p < 0.001, ‘**’ for p < 0.01, ‘*’ for p < 0.05, ‘t’ for p < 0.1 (alpha adjusted for multiple comparisons).

Figure 4

Bars show mean corrected probability to commit novelty responses, in each of the four task quarters for different groups of neotic responses; blue line indicates the smoothed slope by local polynomial regression fitting (locally weighted scatterplot smoothing-loess); the coloured lines indicate the probability to respond to the unrewarded baseline stimuli; shaded areas represent 95% confidence intervals.

Figure 5

Number of individuals per species participating in the task. Shading indicates quartile latencies to respond to either stimulus in the first trial of the task after the touchscreen has been associated with a food reward: Black represents very fast approaching individuals (responding below 5.00 seconds); dark grey indicates fast approaching individuals (responses made between 5.00 and 21.97 seconds); slowly approaching individuals (responding within 21.97 and 66.87 seconds) were assigned medium grey; light grey shows very slowly approaching individuals (requiring more than 66.87 seconds to interact with the stimuli); the red bar indicates missing values of four individuals of kea for which no latencies are available.