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Anim Cogn (2008) 11:651659 DOI 10.1007/s10071-008-0155-2
ORIGINAL PAPER
Sign- and goal-tracking in Atlantic cod (Gadus morhua)
Jonatan Nilsson Tore S. Kristiansen Jan Erik Fosseidengen Anders Fern Ruud van den Bos
Received: 14 September 2007 / Revised: 16 April 2008 / Accepted: 18 April 2008 / Published online: 14 May 2008 Springer-Verlag 2008
Abstract When animals associate a stimulus with food, they may either direct their response towards the stimulus (sign-tracking) or towards the food (goal-tracking). The direction of the conditioned response of cod was investigated to elucidate how cod read cue signals. Groups of cod were conditioned to associate a blinking light (conditioned stimulus, CS) with a food reward (unconditioned stimulus, US), with the CS and the US located at opposite sides of the tank. Two groups were trained in a delay conditioning procedure (CS = 60 s, interstimulus interval = 30 s) and two groups were trained in a trace conditioning procedure (CS = 12 s, trace interval = 20 s). The response pattern was similar for the delay- and trace-conditioned groups. The initial main response at the onset of the CS was approaching the blinking lights, i.e. sign-tracking. In the early trials, the Wsh did not gather in the feeding area before the arrival of food. In the later trials, the Wsh Wrst approached the blinking lights, but then moved across the tank and gathered below the feeder before the food arrived, i.e. sign-tracking followed by goal-tracking within each trial. These two responses are interpreted as reXecting two learning systems,i.e. one rapid, reXexive response directed at the signal (sign-tracking) and one slower, more Xexible response based on expectations about time and place for arrival of
the food (goal-tracking). The ecological signiWcance of these two learning systems in cod is discussed.
Keywords Response systems Pavlovian conditioning Cognition Foraging Fish Learning
Introduction
Interest in the learning capacities of Wsh has increased in recent years, and there is now a large literature on how Wsh can learn to deal with variable ecological challenges in connection with foraging, predator defence, orientation and mating (see Brown et al. 2006 for reviews). Although it is well documented that Wsh can learn to associate stimuli with biologically relevant events (Bull 1928; Overmier and Hollis 1990), it is less well known...