The Poggendorff illusion: a bias in the estimation of the orientation of virtual lines by second-stage filters

نویسنده

  • M. J. Morgan
چکیده

The veridical perception of collinearity between two separated lines is distorted by two parallel lines in the space between them (the Poggendorff illusion). This paper tests the conjecture that the perception of collinearity of separated lines is based on a two-stage mechanism. The first stage encodes the orientation of the virtual line between the proximal terminators of the target lines. The second stage compares this virtual orientation with the orientation of the target lines themselves. Errors can and do arise from either process. Two parallel lines, abutting against the target lines, cause the classical Poggendorff misalignment bias. The magnitude of the bias is increased by Gaussian blur, as is a version of the Poggendorff figure containing only acute angles. In the obtuse-angle figure, on the other hand, blur decreases the misalignment bias. We argue that the acute- and obtuse-angle biases depend upon different mechanisms, and that the obtuse-angle effect is more related to the obtuse-angle version of the Muller-Lyer illusion, which is also decreased by blur. If observers attempt to match the orientation of the virtual line between the two line intersections in the Poggendorff figure they make an error in the same direction as the Poggendorff bias. The orientation of the target lines in the figure, however, is veridically matched to a Gabor-patch probe, unless the target lines are very short, in which case the error is in the same direction as the Poggendorff bias. A small bend in the target lines where they abut the parallels increases the Poggendorff bias if it makes the line more orthogonal to the parallel, but has little effect in the opposite direction. The Poggendorff bias is unlikely to depend upon biases in first-stage linear filters because (a) it still exists in figures composed of short, luminance-balanced lines which are defined by contrast only; and (b) it also exists if the parallels are replaced by grating patches with the same mean luminance as the background. The orientation of the grating in the latter case affects the magnitude of the bias, but even an orientation which should reverse the Poggendorff bias by the mechanism of cross-orientation inhibition fails to do so. The Poggendorff bias is a complex effect arising from several sources. Blurring in second-stage filters with large receptive fields can explain many aspects of the phenomenon.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Bias in Visual Motion Processes: A Theory Predicting Illusions

The first step in the interpretation of video sequences is the estimation of spatio-temporal image representations, that is the image motion or the correspondence of points or lines. Noise in the data, however, causes a serious problem for their estimation; in particular, it causes bias. As a result the location of image points, the orientation of image lines and the length and orientation of i...

متن کامل

Characterisation of the misalignment and misangulation components in the Poggendorff and corner-Poggendorff illusions.

In the Poggendorff illusion, two colinear segments abutting obliquely on an intervening configuration (often consisting of two long parallel lines) appear misaligned. We report here the results of a component analysis of the illusion and several of its variants, including in particular the 'corner-Poggendorff' illusion, and variants with a single arm. Using a nulling method, we determined an 'o...

متن کامل

Fiscal Illusion in Iranian Economy Emphasizing the Five-Dimensional Indicators and the NARDL Approach

The phenomenon of fiscal illusion has always been an intriguing topic in the public finance literature. Fiscal illusion is a concept in which misinterpretation of fiscal parameters and tax expenses and liabilities lead to bias in budgetary decision making at all levels of the government. The current research presents an empirical analysis of the fiscal illusion in the Iranian economy, using fiv...

متن کامل

An Advanced State Estimation Method Using Virtual Meters

-  Power system state estimation is a central component in energy management systems of power system. The goal of state estimation is to determine the system status and power flow of transmission lines. This paper presents an advanced state estimation algorithm based on weighted least square (WLS) criteria by introducing virtual meters. For each bus of network, except slack bus, a virtual meter...

متن کامل

Spatial context affects the Poggendorff illusion.

The Poggendorff illusion has often been explained as purely an interaction between the parallels and the transversals. The present study demonstrates that additional spatial context exerts an influence on this illusion. In Experiment 1, we examined the effects of a surrounding tilted frame (complete and degraded versions) on collinearity adjustments in the upright and rotated Poggendorff figure...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:
  • Vision Research

دوره 39  شماره 

صفحات  -

تاریخ انتشار 1999