Investigating the size weight illusion in upper limb amputees

Sarah Day, Gavin Buckingham

Research output: Contribution to conferenceAbstractpeer-review


The size weight illusion occurs when a person underestimates the weight of a larger object in relation to a
smaller object of the same mass. This is well documented
in normal populations but there has only been one study
looking into its presence in populations with limb loss. This
project aims to expand on the work by Wallace comparing
the performance of a larger sample of upper limb amputees
with able-bodied persons to investigate whether the size
weight illusion exists in amputees and whether it is of the
same magnitude as in the normal population. There are several potential benefits to this study. Currently what causes the size weight illusion is unknown although there are several theories. Testing with active prosthetic users allow the researchers to eliminate certain variables such as sensory feedback as current prostheses used do not provide sensory feedback from the fingers to the user. The findings
from this study also provide a greater understanding of what
information individuals with a prosthetic limb use to judge
the weight of objects, which may have consequences for the
environmental ergonomics of this population.

During our investigation we compared a group of upper
limb amputees using prosthetic devices to a group of people
with normal upper limb function. Approval for the study was
granted by the University of Strathclyde Ethical Committee.
Participants were tested one at a time in separate testing
sessions. Participants were asked to lift objects of varying size and weight and ask them to rate them as a number, with
a larger number indicating a larger weight. This number was
then used to determine if the participants were experiencing
the size weight illusion. The order in which the objects were
offered to the participants was random and different for each
participant. The data was analysed using T-tests and ANOVA with the SPSS software package.

The data collection phase is due to be completed on 31/3/14. To date we have collected data on 5 amputee and 5 control subjects.

Preliminary analysis of the data shows that the amputee
group did experience the size weight illusion. This supports
the previous findings by Wallace. Interestingly, the magnitude
of the illusion and sensitivity to weight appear to be different
according to the subject groups, although this will be confirmed upon completion of the data collection
Original languageEnglish
Number of pages1
Publication statusPublished - 22 Aug 2014
EventMEC 14: Myoelectric Controls Symposium - Fredericton, Canada
Duration: 19 Aug 201422 Aug 2014


ConferenceMEC 14: Myoelectric Controls Symposium
Abbreviated titleMEC 14


  • size weight illusion
  • upper limb amputees
  • prosthetic devices


Dive into the research topics of 'Investigating the size weight illusion in upper limb amputees'. Together they form a unique fingerprint.

Cite this