The Effect of Orientation on Accuracy of the T- illusion
Abstract
The T-illusion study was experimented by 58 Psychology students to conclude whether the orientation
of a T-shape can affect the accuracy of equality. The research question for the study was “In which
orientation do we overestimate or underestimate the critical line in the T-shape?” In order to do so the
participants had to follow a method. The lines were to be judged on their equality at different start
points with the critical line being longer and shorter. Participants were presented with a number of
several trials to identify which vertical line was longer. This was done using a counter-balanced
design, meaning that the conditions differed for the participants. The findings were that the results
between the horizontal and vertical lines were both underestimated with quite similar percentages
following the Bisection theory. This supported my prediction as I believed that the orientation would
make no difference to the effect.
Participants
58 Psychology students were participants in the experiment. The age range within the study was from
18 to 42 years of age, meaning that the mean age within the study was 20.95 and the standard
deviation was 5.70. The gender split was 9.43 which consisted of 53 females and five males. Each
student was assigned to a lab partner in which they took turns in being the participant/experimenter.
The experiment was completed in a lab with a teacher present to observe and ensure everyone was
abiding the rules (I.e. no hinting or discussing results, which could’ve increased critical line
accuracy).
Design
The design of the study was a within subjects' design, that was both a repeated measure and paired
sample. The independent variable was the orientation which had 2 levels being horizontal and
vertical, whilst the dependent variable was the accuracy of the line.
Apparatus
The participants conducted the experiment on a Mac computer, the ratio was two students to a
computer. Participants were required to visit the stimulus website (https://dangurn.github.io/HV-
illusion/) in which the programme would be ready to adjust and use to begin the experiment.
Procedure
Upon arrival to the experiment, participants were debriefed on the study. Each participant was
required to adjust their chair so eyes were level with screen and an estimate of 40cm away. The
participant was then introduced to an online stimulus of the T in which they either had to lengthen or
shorten using the + and – keys until they thought the length of the critical line was equal to the other
line. This would be repeated 16 times, 4 shortening and 4 lengthening of horizontal and then the same
thing for a vertical T. The conditions were that the experimenter couldn't assist them in any way by
hinting to answers or allowing participants to see their results.
Abstract
The T-illusion study was experimented by 58 Psychology students to conclude whether the orientation
of a T-shape can affect the accuracy of equality. The research question for the study was “In which
orientation do we overestimate or underestimate the critical line in the T-shape?” In order to do so the
participants had to follow a method. The lines were to be judged on their equality at different start
points with the critical line being longer and shorter. Participants were presented with a number of
several trials to identify which vertical line was longer. This was done using a counter-balanced
design, meaning that the conditions differed for the participants. The findings were that the results
between the horizontal and vertical lines were both underestimated with quite similar percentages
following the Bisection theory. This supported my prediction as I believed that the orientation would
make no difference to the effect.
Participants
58 Psychology students were participants in the experiment. The age range within the study was from
18 to 42 years of age, meaning that the mean age within the study was 20.95 and the standard
deviation was 5.70. The gender split was 9.43 which consisted of 53 females and five males. Each
student was assigned to a lab partner in which they took turns in being the participant/experimenter.
The experiment was completed in a lab with a teacher present to observe and ensure everyone was
abiding the rules (I.e. no hinting or discussing results, which could’ve increased critical line
accuracy).
Design
The design of the study was a within subjects' design, that was both a repeated measure and paired
sample. The independent variable was the orientation which had 2 levels being horizontal and
vertical, whilst the dependent variable was the accuracy of the line.
Apparatus
The participants conducted the experiment on a Mac computer, the ratio was two students to a
computer. Participants were required to visit the stimulus website (https://dangurn.github.io/HV-
illusion/) in which the programme would be ready to adjust and use to begin the experiment.
Procedure
Upon arrival to the experiment, participants were debriefed on the study. Each participant was
required to adjust their chair so eyes were level with screen and an estimate of 40cm away. The
participant was then introduced to an online stimulus of the T in which they either had to lengthen or
shorten using the + and – keys until they thought the length of the critical line was equal to the other
line. This would be repeated 16 times, 4 shortening and 4 lengthening of horizontal and then the same
thing for a vertical T. The conditions were that the experimenter couldn't assist them in any way by
hinting to answers or allowing participants to see their results.
