False-belief understanding i 2.5-year-olds: evidence for violation-of-expectation change-of-location and unexpected-contents tasks

Abstract

Until recently, it was generally assumed that the ability to attribute false beliefs did not emerge until about 4 years of age. However, recent reports using spontaneous- as opposed to elicited-response tasks have suggested that this ability may be present much earlier. To date, researchers have employed two kinds of spontaneous-response false-belief tasks: violation-of-expectation tasks have been used with infants in the second year of life, and anticipatory-looking tasks have been used with toddlers in the third year of life. In the present research, 2.5-year-old toddlers were tested in violation-of-expectation tasks involving a change-of-location situation (Experiment 1) and an unexpected-contents situation (Experiment 2). Results were positive in both situations, providing the first demonstrations of false-belief understanding in toddlers using violation-of-expectation tasks and, as such, pointing to a consistent and continuous picture of early false-belief understanding.

Figure 1

Schematic drawing of the familiarization trials in Experiment 1. False-belief and ignorance conditions: During the (40-s) initial phase of the left-container familiarization trial in the false-belief and ignorance conditions, the agent (in the back window) first slid open the green curtain filling her window, and then the experimenter (in the right window) said `Watch!' and hid the toy frog in the left container. Next, the agent closed the green curtain, and the experimenter counted aloud to 10. The agent then returned and the experimenter asked `Where is the toy?' During the final phase of the trial, the agent first said `Here it is!' while pointing to the left container (1 s) and then tapped the knob on the container's lid four times (4 s); this 5-s sequence was repeated until the trial ended. In the right-container familiarization trial, the experimenter hid the toy in the right container and the agent pointed to the right container. Knowledge condition: The agent remained present throughout the knowledge condition familiarization trials: instead of opening and closing the green curtain, she moved the open curtain from one side of her window to the other.

Figure 2

Schematic drawing of the test trials in Experiment 1. False-belief condition: The points-left test trial in the false-belief condition was identical to the left-container familiarization trial in the same condition, except that the experimenter moved the toy to the right container while she counted aloud. In the points-right test trial, the agent pointed to the right container in the final phase of the trial. Knowledge condition: The agent remained present throughout the knowledge condition test trials: instead of opening and closing the green curtain, she moved the open curtain from one side of her window to the other. Ignorance condition: The ignorance condition test trials were identical to those in the false-belief condition with one exception: in each test trial, after placing the toy into the left container, the experimenter immediately took it out again. After the agent closed the green curtain, the experimenter hid the toy in the right container while she counted aloud.

Figure 3

Mean looking times of the children in the false-belief, knowledge, and ignorance conditions of Experiment 1 during the final phase of the points-left or points-right test trial. Error bars represent standard errors, and asterisks indicate significant differences (p < .05 or better).

Figure 4

Schematic drawing of the set-up for the familiarization trials of Experiment 2. False-belief condition: At the start of the false-belief condition familiarization trial, only the experimenter was present (the green curtain was closed). On the apparatus floor were a crayon box (containing six crayons) and a cheerio box (containing about 50 cheerios); in front of each box was a transparent tray. During the (65-s) initial phase of the trial, the experimenter emptied the cheerio box into its tray, emptied the crayon box into its tray, switched the two trays, placed the crayons inside the cheerio box, and finally poured the cheerios into the crayon box. During the final phase of the trial, the experimenter paused as shown until the trial ended. Knowledge condition: In the knowledge condition familiarization trial, the agent was present (the green curtain was open) throughout the trial. Reverse-false-belief condition: The infants in the reverse-false-belief condition received two familiarization trials. The first was identical to that in the knowledge condition; in the second, the agent was absent (the green curtain was closed), and the experimenter repeated the actions she had performed before and thus effectively restored the boxes' original contents.

Figure 5

Schematic drawing of the test trials in Experiment 2. Eat group: During the (18-s) initial phase of the matching-box trial, the agent opened the green curtain and said `I want to eat. I'll get the Cheerios', while looking at a neutral mark on the apparatus floor between the two trays. During the final phase of the trial, the agent first said `Here they are!' while pointing to the cheerio box (1 s) and then tapped the top of the box four times (4 s); this 5-s sequence was repeated until the trial ended. In the non-matching-box trial, the agent pointed to the crayon box. Color group: The color group test trials were identical except that the agent said `I want to color. I'll get the crayons', and pointed to the crayon box in the matching-box trial and to the cheerio box in the non-matching-box trial.

Figure 6

Mean looking times of the children in the false-belief, knowledge, and reverse-false-belief conditions of Experiment 2 during the final phase of the matching- and non-matching-box test trials. Error bars represent standard errors, and asterisks indicate significant differences (p < .05 or better).