Point-Light Sequence Preferences

<div><p>(A) Preferences (group means and the standard error of the mean) estimated as the percentage of time spent close to the walking hen.</p> <p>(B) Preferences are shown as the percentage of time spent close to the scrambled hen.</p> <p>(C) Preferences are shown as the percentage of time spent close to the walking cat.</p> <p>Asterisks indicate significant departures from chance level (i.e., 50%) estimated by one-sample two-tailed <i>t</i> tests (*<i>p</i> < 0.05; **<i>p</i> < 0.01; ***<i>p</i> < 0.001).</p></div

Results of Experiment 1(5vs.10), Experiment 2 (6vs.9) and Experiment 3 (10vs.20).

<p>Choice (means with SEM) displayed at testing by the chicks, expressed as a preference for the stimulus associated with food.</p

Schematic Representation of the Test Apparatus

<p>Schematic Representation of the Test Apparatus</p

Point-Light Displays and Sample Frames from the Animation Sequences

<div><p>(A) The walking hen point-light display (above) The filled circles indicate the location of each point of light.</p> <p>(B) Six frames sampled from the walking hen animation (below)</p> <p>(C) The walking cat point-light display (above).</p> <p>(D) Six frames sampled from the walking cat animation (below).</p></div

The experimental stimuli.

<p>The experimental stimuli used for the shaping (a), discrimination training (b) and the generalization testing phases (c) for Experiments 1 and 2. The main difference between aligned (BAL) and misaligned (IMBAL) conditions was the position of the second dot from the top, which was presented off-axis and therefor misaligned in the IMBAL condition. During the generalization phase, “spread apart” versions of the training stimuli, obtained by increasing the distance between the dots, were used (compare Figs. 2b and c., which allowed us to test whether BAL- and IMBAL-chicks differed in their generalization ability). In Experiment 2, fewer dots were presented thereby reducing the amount of information over the same spatial range and increasing axial noncoherence. If chicks demonstrated a consistent preference in both Experiments 1 and 2, this consistency could be attributable to an evaluation of implicit structure rather than a preference for the shape itself.</p

A schematic representation of the apparatus.

<p>The food-box is denoted by A while B indicates the movable partition. A movable lamp providing illumination to the inside of the apparatus is represented above it. At the beginning of each trial, removing the partition, we allowed the chick to reach for the food box. This figure represents the initial training, when chicks are shaped to peck to the one-dot stimulus (Fig. 2a): the chick is rewarded (by opening the food box for a few seconds, allowing the ingestion of some food grains) for each peck at the stimulus. Then the experimenters close the food box and confine the chick behind partition B (the starting position for the following trial). In the subsequent discrimination training two food boxes are presented side by side, and the chick has to choose which one to peck on the basis of the stimulus displayed on it (an aligned or a misaligned configuration of dots, Fig. 2b). After a correct response (a peck on S+) the animal is rewarded (see above), whereas after an incorrect response the chick will be confined behind partition B for 15 s without access to food. The procedure used at test differs only in that the chick is always reinforced for each peck at either stimulus (see Fig. 2c).</p

Results of Experiments 1 and 2.

<p>The proportion of trials (of 20) upon which chicks showed a preference to approach and peck the target stimulus in the generalization phase, as a function of training on aligned (BAL) or misaligned (IMBAL) training stimuli. The number of occasions upon which chicks showed a category preference consistent with their training was significantly different between the IMBAL- and BAL-chicks in both Experiments 1 and 2.</p

Example of one the control noise stimuli used in the newborns' study.

<p>The same stimulus reproduced in this figure was also used with chicks in Experiment 2. See also <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0018802#pone.0018802-Csibra1" target="_blank">[15]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0018802#pone.0018802-Blasi1" target="_blank">[16]</a> for the face stimuli employed.</p

Newborn human babies.

<p>Newborn human babies.</p